diff --git a/package.json b/package.json
index b61b673d5..56bd46fbf 100644
--- a/package.json
+++ b/package.json
@@ -34,6 +34,7 @@
   "scripts": {
     "check": "yarn clean && yarn lint && yarn prepack:all && yarn test",
     "lint": "eslint packages && lerna run tslint",
+    "lint:fix": "eslint --fix 'packages/**/*.{ts,js}'",
     "flow": "flow",
     "flow:check": "flow check",
     "test": "lerna run --concurrency 1 test",
diff --git a/packages/graphile-build-pg/src/GraphQLJSON.js b/packages/graphile-build-pg/src/GraphQLJSON.ts
similarity index 100%
rename from packages/graphile-build-pg/src/GraphQLJSON.js
rename to packages/graphile-build-pg/src/GraphQLJSON.ts
diff --git a/packages/graphile-build-pg/src/PgLiveProvider.js b/packages/graphile-build-pg/src/PgLiveProvider.ts
similarity index 92%
rename from packages/graphile-build-pg/src/PgLiveProvider.js
rename to packages/graphile-build-pg/src/PgLiveProvider.ts
index 4a42c9a7e..020895da2 100644
--- a/packages/graphile-build-pg/src/PgLiveProvider.js
+++ b/packages/graphile-build-pg/src/PgLiveProvider.ts
@@ -1,6 +1,5 @@
-// @flow
 import { LiveProvider } from "graphile-build";
-import type { PgClass } from "./plugins/PgIntrospectionPlugin";
+import { PgClass } from "./plugins/PgIntrospectionPlugin";
 
 export default class PgLiveProvider extends LiveProvider {
   // eslint-disable-next-line flowtype/no-weak-types
diff --git a/packages/graphile-build-pg/src/QueryBuilder.js b/packages/graphile-build-pg/src/QueryBuilder.ts
similarity index 92%
rename from packages/graphile-build-pg/src/QueryBuilder.js
rename to packages/graphile-build-pg/src/QueryBuilder.ts
index 11c207604..6640eee13 100644
--- a/packages/graphile-build-pg/src/QueryBuilder.js
+++ b/packages/graphile-build-pg/src/QueryBuilder.ts
@@ -1,9 +1,8 @@
-// @flow
 import * as sql from "pg-sql2";
-import type { SQL } from "pg-sql2";
+import { SQL } from "pg-sql2";
 import isSafeInteger from "lodash/isSafeInteger";
 import chunk from "lodash/chunk";
-import type { PgClass, PgType } from "./plugins/PgIntrospectionPlugin";
+import { PgClass, PgType } from "./plugins/PgIntrospectionPlugin";
 
 // eslint-disable-next-line flowtype/no-weak-types
 type GraphQLContext = any;
@@ -11,8 +10,9 @@ type GraphQLContext = any;
 const isDev = process.env.POSTGRAPHILE_ENV === "development";
 
 type GenContext = {
-  queryBuilder: QueryBuilder,
+  queryBuilder: QueryBuilder;
 };
+
 type Gen<T> = (context: GenContext) => T;
 
 function callIfNecessary<T>(o: Gen<T> | T, context: GenContext): T {
@@ -39,10 +39,10 @@ type SQLAlias = SQL;
 type SQLGen = Gen<SQL> | SQL;
 type NumberGen = Gen<number> | number;
 type CursorValue = {};
-type CursorComparator = (val: CursorValue, isAfter: boolean) => void;
+type CursorComparator = (val: CursorValue, isAfter: boolean) => undefined;
 
 export type QueryBuilderOptions = {
-  supportsJSONB?: boolean, // Defaults to true
+  supportsJSONB?: boolean;
 };
 
 function escapeLarge(sqlFragment: SQL, type: PgType) {
@@ -66,62 +66,71 @@ function escapeLarge(sqlFragment: SQL, type: PgType) {
 }
 
 class QueryBuilder {
-  parentQueryBuilder: QueryBuilder | void;
+  parentQueryBuilder: QueryBuilder | undefined;
   context: GraphQLContext;
   rootValue: any; // eslint-disable-line flowtype/no-weak-types
   supportsJSONB: boolean;
   locks: {
-    [string]: false | true | string,
+    [a: string]: false | true | string;
   };
+
   finalized: boolean;
   selectedIdentifiers: boolean;
   data: {
-    cursorPrefix: Array<string>,
-    select: Array<[SQLGen, RawAlias]>,
-    selectCursor: ?SQLGen,
-    from: ?[SQLGen, SQLAlias],
-    join: Array<SQLGen>,
-    where: Array<SQLGen>,
+    cursorPrefix: Array<string>;
+    select: Array<[SQLGen, RawAlias]>;
+    selectCursor: SQLGen | null | undefined;
+    from: [SQLGen, SQLAlias] | null | undefined;
+    join: Array<SQLGen>;
+    where: Array<SQLGen>;
     whereBound: {
-      lower: Array<SQLGen>,
-      upper: Array<SQLGen>,
-    },
-    orderBy: Array<[SQLGen, boolean, boolean | null]>,
-    orderIsUnique: boolean,
-    limit: ?NumberGen,
-    offset: ?NumberGen,
-    first: ?number,
-    last: ?number,
+      lower: Array<SQLGen>;
+      upper: Array<SQLGen>;
+    };
+
+    orderBy: Array<[SQLGen, boolean, boolean | null]>;
+    orderIsUnique: boolean;
+    limit: NumberGen | null | undefined;
+    offset: NumberGen | null | undefined;
+    first: number | null | undefined;
+    last: number | null | undefined;
     beforeLock: {
-      [string]: Array<() => void> | null,
-    },
-    cursorComparator: ?CursorComparator,
+      [a: string]: Array<() => undefined> | null;
+    };
+
+    cursorComparator: CursorComparator | null | undefined;
     liveConditions: Array<
       // eslint-disable-next-line flowtype/no-weak-types
-      [(data: {}) => (record: any) => boolean, { [key: string]: SQL } | void]
-    >,
+      [
+        (data: {}) => (record: any) => boolean,
+        { [key: string]: SQL } | undefined
+      ]
+    >;
   };
+
   compiledData: {
-    cursorPrefix: Array<string>,
-    select: Array<[SQL, RawAlias]>,
-    selectCursor: ?SQL,
-    from: ?[SQL, SQLAlias],
-    join: Array<SQL>,
-    where: Array<SQL>,
+    cursorPrefix: Array<string>;
+    select: Array<[SQL, RawAlias]>;
+    selectCursor: SQL | null | undefined;
+    from: [SQL, SQLAlias] | null | undefined;
+    join: Array<SQL>;
+    where: Array<SQL>;
     whereBound: {
-      lower: Array<SQL>,
-      upper: Array<SQL>,
-    },
-    orderBy: Array<[SQL, boolean, boolean | null]>,
-    orderIsUnique: boolean,
-    limit: ?number,
-    offset: ?number,
-    first: ?number,
-    last: ?number,
-    cursorComparator: ?CursorComparator,
+      lower: Array<SQL>;
+      upper: Array<SQL>;
+    };
+
+    orderBy: Array<[SQL, boolean, boolean | null]>;
+    orderIsUnique: boolean;
+    limit: number | null | undefined;
+    offset: number | null | undefined;
+    first: number | null | undefined;
+    last: number | null | undefined;
+    cursorComparator: CursorComparator | null | undefined;
   };
+
   lockContext: {
-    queryBuilder: QueryBuilder,
+    queryBuilder: QueryBuilder;
   };
 
   constructor(
@@ -154,6 +163,7 @@ class QueryBuilder {
       limit: false,
       offset: false,
     };
+
     this.finalized = false;
     this.selectedIdentifiers = false;
     this.data = {
@@ -168,6 +178,7 @@ class QueryBuilder {
         lower: [],
         upper: [],
       },
+
       orderBy: [],
       orderIsUnique: false,
       limit: null,
@@ -191,9 +202,11 @@ class QueryBuilder {
         limit: [],
         offset: [],
       },
+
       cursorComparator: null,
       liveConditions: [],
     };
+
     this.compiledData = {
       cursorPrefix: ["natural"],
       select: [],
@@ -205,6 +218,7 @@ class QueryBuilder {
         lower: [],
         upper: [],
       },
+
       orderBy: [],
       orderIsUnique: false,
       limit: null,
@@ -213,6 +227,7 @@ class QueryBuilder {
       last: null,
       cursorComparator: null,
     };
+
     this.beforeLock("select", () => {
       this.lock("selectCursor");
       if (this.compiledData.selectCursor) {
@@ -254,6 +269,7 @@ class QueryBuilder {
             ([expr, alias]) =>
               sql.fragment`${sql.literal(alias)}::text, ${expr}`
           ),
+
           ", "
         )})`;
       return sql.fragment`(${sql.join(
@@ -266,6 +282,7 @@ class QueryBuilder {
         fields.map(
           ([expr, alias]) => sql.fragment`${sql.literal(alias)}::text, ${expr}`
         ),
+
         ", "
       )})`;
     }
@@ -273,7 +290,7 @@ class QueryBuilder {
 
   // ----------------------------------------
 
-  beforeLock(field: string, fn: () => void) {
+  beforeLock(field: string, fn: () => undefined) {
     this.checkLock(field);
     if (!this.data.beforeLock[field]) {
       this.data.beforeLock[field] = [];
@@ -285,7 +302,7 @@ class QueryBuilder {
   makeLiveCollection(
     table: PgClass,
     // eslint-disable-next-line flowtype/no-weak-types
-    cb?: (checker: (data: any) => (record: any) => boolean) => void
+    cb?: (checker: (data: any) => (record: any) => boolean) => undefined
   ) {
     /* the actual condition doesn't matter hugely, 'select' should work */
     if (!this.rootValue || !this.rootValue.liveConditions) return;
@@ -295,6 +312,7 @@ class QueryBuilder {
       const checkers = liveConditions.map(([checkerGenerator]) =>
         checkerGenerator(data)
       );
+
       return record => checkers.every(checker => checker(record));
     };
     if (this.parentQueryBuilder) {
@@ -311,6 +329,7 @@ class QueryBuilder {
             requirements ? Object.assign(memo, requirements) : memo,
           {}
         );
+
         // $FlowFixMe
         this.parentQueryBuilder.select(
           sql.fragment`\
@@ -319,6 +338,7 @@ ${sql.join(
   Object.keys(allRequirements).map(
     key => sql.fragment`, ${sql.literal(key)}::text, ${allRequirements[key]}`
   ),
+
   ""
 )})`,
           "__live"
@@ -392,10 +412,12 @@ ${sql.join(
             key.type
           )
         ),
+
         ", "
       )})`,
       "__identifiers"
     );
+
     this.selectedIdentifiers = true;
   }
   selectCursor(exprGen: SQLGen) {
@@ -574,6 +596,7 @@ ${sql.join(
         ([sqlFragment, alias]) =>
           sql.fragment`to_json(${sqlFragment}) as ${sql.identifier(alias)}`
       ),
+
       ", "
     );
   }
@@ -581,8 +604,8 @@ ${sql.join(
     addNullCase,
     addNotDistinctFromNullCase,
   }: {
-    addNullCase?: boolean,
-    addNotDistinctFromNullCase?: boolean,
+    addNullCase?: boolean;
+    addNotDistinctFromNullCase?: boolean;
   }) {
     this.lockEverything();
     let buildObject = this.compiledData.select.length
@@ -622,7 +645,7 @@ ${sql.join(
     {
       addNullCase,
       addNotDistinctFromNullCase,
-    }: { addNullCase?: boolean, addNotDistinctFromNullCase?: boolean }
+    }: { addNullCase?: boolean; addNotDistinctFromNullCase?: boolean }
   ) {
     this.lock("where");
     const clauses = [
@@ -658,18 +681,19 @@ ${sql.join(
       ...(includeLowerBound ? [this.buildWhereBoundClause(true)] : []),
       ...(includeUpperBound ? [this.buildWhereBoundClause(false)] : []),
     ];
+
     return clauses.length
       ? sql.fragment`(${sql.join(clauses, ") and (")})`
       : sql.fragment`1 = 1`;
   }
   build(
     options: {
-      asJson?: boolean,
-      asJsonAggregate?: boolean,
-      onlyJsonField?: boolean,
-      addNullCase?: boolean,
-      addNotDistinctFromNullCase?: boolean,
-      useAsterisk?: boolean,
+      asJson?: boolean;
+      asJsonAggregate?: boolean;
+      onlyJsonField?: boolean;
+      addNullCase?: boolean;
+      addNotDistinctFromNullCase?: boolean;
+      useAsterisk?: boolean;
     } = {}
   ) {
     const {
@@ -717,6 +741,7 @@ ${
                 : null
             }`
         ),
+
         ","
       )}`
     : ""
@@ -775,6 +800,7 @@ order by (row_number() over (partition by 1)) desc`;
         this.data[type].lower,
         context
       );
+
       this.compiledData[type].upper = callIfNecessaryArray(
         this.data[type].upper,
         context
diff --git a/packages/graphile-build-pg/src/index.js b/packages/graphile-build-pg/src/index.ts
similarity index 99%
rename from packages/graphile-build-pg/src/index.js
rename to packages/graphile-build-pg/src/index.ts
index 4701c1add..f46db7651 100644
--- a/packages/graphile-build-pg/src/index.js
+++ b/packages/graphile-build-pg/src/index.ts
@@ -1,4 +1,3 @@
-// @flow
 import PgBasicsPlugin from "./plugins/PgBasicsPlugin";
 import PgIntrospectionPlugin from "./plugins/PgIntrospectionPlugin";
 import PgTypesPlugin from "./plugins/PgTypesPlugin";
diff --git a/packages/graphile-build-pg/src/inflections.js b/packages/graphile-build-pg/src/inflections.ts
similarity index 77%
rename from packages/graphile-build-pg/src/inflections.js
rename to packages/graphile-build-pg/src/inflections.ts
index 6b1fb7bd2..19e2e7f81 100644
--- a/packages/graphile-build-pg/src/inflections.js
+++ b/packages/graphile-build-pg/src/inflections.ts
@@ -1,5 +1,5 @@
 /* THIS ENTIRE FILE IS DEPRECATED. DO NOT USE THIS. DO NOT EDIT THIS. */
-// @flow
+
 import {
   upperCamelCase,
   camelCase,
@@ -29,30 +29,31 @@ function deprecate(fn: (...input: Array<any>) => string, message: string) {
 
 function deprecateEverything(obj: {
   // eslint-disable-next-line flowtype/no-weak-types
-  [string]: (...input: Array<any>) => string,
+  [a: string]: (...input: Array<any>) => string;
 }) {
   return Object.keys(obj).reduce((memo, key) => {
     memo[key] = deprecate(
       obj[key],
       `Something (probably a plugin) called the old inflection system (inflector: '${key}'). This system has been deprecated since 4.0.0-beta.6 (4th May 2018) and is not used internally so using it may cause inconsistencies, instead please use the plugin-capable inflection system https://www.graphile.org/postgraphile/inflection/`
     );
+
     return memo;
   }, {});
 }
 
 type Keys = Array<{
-  column: string,
-  table: string,
-  schema: ?string,
+  column: string;
+  table: string;
+  schema: string | null | undefined;
 }>;
 
-type InflectorUtils = {|
-  constantCase: string => string,
-  camelCase: string => string,
-  upperCamelCase: string => string,
-  pluralize: string => string,
-  singularize: string => string,
-|};
+type InflectorUtils = {
+  constantCase: (a: string) => string;
+  camelCase: (a: string) => string;
+  upperCamelCase: (a: string) => string;
+  pluralize: (a: string) => string;
+  singularize: (a: string) => string;
+};
 
 export const defaultUtils: InflectorUtils = {
   constantCase,
@@ -65,11 +66,11 @@ export const defaultUtils: InflectorUtils = {
 export type Inflector = {
   // TODO: tighten this up!
   // eslint-disable-next-line flowtype/no-weak-types
-  [string]: (...input: Array<any>) => string,
+  [a: string]: (...input: Array<any>) => string;
 };
 
 export const newInflector = (
-  overrides: ?{ [string]: () => string } = undefined,
+  overrides: { [a: string]: () => string } | null | undefined = undefined,
   {
     constantCase,
     camelCase,
@@ -88,7 +89,7 @@ export const newInflector = (
   return deprecateEverything(
     preventEmptyResult({
       pluralize,
-      argument(name: ?string, index: number) {
+      argument(name: string | null | undefined, index: number) {
         return camelCase(name || `arg${index}`);
       },
       orderByType(typeName: string) {
@@ -98,7 +99,7 @@ export const newInflector = (
         name: string,
         ascending: boolean,
         _table: string,
-        _schema: ?string
+        _schema: string | null | undefined
       ) {
         return constantCase(`${name}_${ascending ? "asc" : "desc"}`);
       },
@@ -207,68 +208,84 @@ export const newInflector = (
       patchField(itemName: string) {
         return camelCase(`${itemName}-patch`);
       },
-      tableName(name: string, _schema: ?string) {
+      tableName(name: string, _schema: string | null | undefined) {
         return camelCase(singularizeTable(name));
       },
-      tableNode(name: string, _schema: ?string) {
+      tableNode(name: string, _schema: string | null | undefined) {
         return camelCase(singularizeTable(name));
       },
-      allRows(name: string, schema: ?string) {
+      allRows(name: string, schema: string | null | undefined) {
         return camelCase(`all-${this.pluralize(this.tableName(name, schema))}`);
       },
-      functionName(name: string, _schema: ?string) {
+      functionName(name: string, _schema: string | null | undefined) {
         return camelCase(name);
       },
-      functionPayloadType(name: string, _schema: ?string) {
+      functionPayloadType(name: string, _schema: string | null | undefined) {
         return upperCamelCase(`${name}-payload`);
       },
-      functionInputType(name: string, _schema: ?string) {
+      functionInputType(name: string, _schema: string | null | undefined) {
         return upperCamelCase(`${name}-input`);
       },
-      tableType(name: string, schema: ?string) {
+      tableType(name: string, schema: string | null | undefined) {
         return upperCamelCase(this.tableName(name, schema));
       },
-      column(name: string, _table: string, _schema: ?string) {
+      column(name: string, _table: string, _schema: string | null | undefined) {
         return camelCase(name);
       },
-      singleRelationByKeys(detailedKeys: Keys, table: string, schema: ?string) {
+      singleRelationByKeys(
+        detailedKeys: Keys,
+        table: string,
+        schema: string | null | undefined
+      ) {
         return camelCase(
           `${this.tableName(table, schema)}-by-${detailedKeys
             .map(key => this.column(key.column, key.table, key.schema))
             .join("-and-")}`
         );
       },
-      rowByUniqueKeys(detailedKeys: Keys, table: string, schema: ?string) {
+      rowByUniqueKeys(
+        detailedKeys: Keys,
+        table: string,
+        schema: string | null | undefined
+      ) {
         return camelCase(
           `${this.tableName(table, schema)}-by-${detailedKeys
             .map(key => this.column(key.column, key.table, key.schema))
             .join("-and-")}`
         );
       },
-      updateByKeys(detailedKeys: Keys, table: string, schema: ?string) {
+      updateByKeys(
+        detailedKeys: Keys,
+        table: string,
+        schema: string | null | undefined
+      ) {
         return camelCase(
           `update-${this.tableName(table, schema)}-by-${detailedKeys
             .map(key => this.column(key.column, key.table, key.schema))
             .join("-and-")}`
         );
       },
-      deleteByKeys(detailedKeys: Keys, table: string, schema: ?string) {
+      deleteByKeys(
+        detailedKeys: Keys,
+        table: string,
+        schema: string | null | undefined
+      ) {
         return camelCase(
           `delete-${this.tableName(table, schema)}-by-${detailedKeys
             .map(key => this.column(key.column, key.table, key.schema))
             .join("-and-")}`
         );
       },
-      updateNode(name: string, _schema: ?string) {
+      updateNode(name: string, _schema: string | null | undefined) {
         return camelCase(`update-${singularizeTable(name)}`);
       },
-      deleteNode(name: string, _schema: ?string) {
+      deleteNode(name: string, _schema: string | null | undefined) {
         return camelCase(`delete-${singularizeTable(name)}`);
       },
       updateByKeysInputType(
         detailedKeys: Keys,
         name: string,
-        _schema: ?string
+        _schema: string | null | undefined
       ) {
         return upperCamelCase(
           `update-${singularizeTable(name)}-by-${detailedKeys
@@ -279,7 +296,7 @@ export const newInflector = (
       deleteByKeysInputType(
         detailedKeys: Keys,
         name: string,
-        _schema: ?string
+        _schema: string | null | undefined
       ) {
         return upperCamelCase(
           `delete-${singularizeTable(name)}-by-${detailedKeys
@@ -287,18 +304,18 @@ export const newInflector = (
             .join("-and-")}-input`
         );
       },
-      updateNodeInputType(name: string, _schema: ?string) {
+      updateNodeInputType(name: string, _schema: string | null | undefined) {
         return upperCamelCase(`update-${singularizeTable(name)}-input`);
       },
-      deleteNodeInputType(name: string, _schema: ?string) {
+      deleteNodeInputType(name: string, _schema: string | null | undefined) {
         return upperCamelCase(`delete-${singularizeTable(name)}-input`);
       },
       manyRelationByKeys(
         detailedKeys: Keys,
         table: string,
-        schema: ?string,
+        schema: string | null | undefined,
         _foreignTable: string,
-        _foreignSchema: ?string
+        _foreignSchema: string | null | undefined
       ) {
         return camelCase(
           `${this.pluralize(
@@ -311,31 +328,37 @@ export const newInflector = (
       edge(typeName: string) {
         return upperCamelCase(`${pluralize(typeName)}-edge`);
       },
-      edgeField(name: string, _schema: ?string) {
+      edgeField(name: string, _schema: string | null | undefined) {
         return camelCase(`${singularizeTable(name)}-edge`);
       },
       connection(typeName: string) {
         return upperCamelCase(`${this.pluralize(typeName)}-connection`);
       },
-      scalarFunctionConnection(procName: string, _procSchema: ?string) {
+      scalarFunctionConnection(
+        procName: string,
+        _procSchema: string | null | undefined
+      ) {
         return upperCamelCase(`${procName}-connection`);
       },
-      scalarFunctionEdge(procName: string, _procSchema: ?string) {
+      scalarFunctionEdge(
+        procName: string,
+        _procSchema: string | null | undefined
+      ) {
         return upperCamelCase(`${procName}-edge`);
       },
-      createField(name: string, _schema: ?string) {
+      createField(name: string, _schema: string | null | undefined) {
         return camelCase(`create-${singularizeTable(name)}`);
       },
-      createInputType(name: string, _schema: ?string) {
+      createInputType(name: string, _schema: string | null | undefined) {
         return upperCamelCase(`create-${singularizeTable(name)}-input`);
       },
-      createPayloadType(name: string, _schema: ?string) {
+      createPayloadType(name: string, _schema: string | null | undefined) {
         return upperCamelCase(`create-${singularizeTable(name)}-payload`);
       },
-      updatePayloadType(name: string, _schema: ?string) {
+      updatePayloadType(name: string, _schema: string | null | undefined) {
         return upperCamelCase(`update-${singularizeTable(name)}-payload`);
       },
-      deletePayloadType(name: string, _schema: ?string) {
+      deletePayloadType(name: string, _schema: string | null | undefined) {
         return upperCamelCase(`delete-${singularizeTable(name)}-payload`);
       },
       ...overrides,
diff --git a/packages/graphile-build-pg/src/omit.js b/packages/graphile-build-pg/src/omit.ts
similarity index 99%
rename from packages/graphile-build-pg/src/omit.js
rename to packages/graphile-build-pg/src/omit.ts
index 8c9491244..618ed8fbc 100644
--- a/packages/graphile-build-pg/src/omit.js
+++ b/packages/graphile-build-pg/src/omit.ts
@@ -1,6 +1,4 @@
-// @flow
-
-import type {
+import {
   PgProc,
   PgClass,
   PgAttribute,
@@ -67,6 +65,7 @@ function parse(arrOrNot, errorPrefix = "Error") {
       }
     })
   );
+
   if (all) {
     return true;
   }
@@ -98,6 +97,7 @@ export default function omit(
       entity.name
     }'`
   );
+
   const includeSpec = parse(
     includeSpecRaw,
     `Error when processing @include instructions for ${entity.kind} '${
@@ -113,6 +113,7 @@ export default function omit(
       const bad = PERMISSIONS_THAT_REQUIRE_READ.filter(
         p => omitSpec.indexOf(p) === -1
       );
+
       if (bad.length > 0) {
         throw new Error(
           `Processing @omit for ${entity.kind} '${entity.name}' - '${bad.join(
@@ -136,6 +137,7 @@ export default function omit(
       const bad = PERMISSIONS_THAT_REQUIRE_READ.find(
         p => includeSpec.indexOf(p) >= 0
       );
+
       if (bad) {
         throw new Error(
           `Error when processing @include for ${entity.kind} '${
diff --git a/packages/graphile-build-pg/src/parseIdentifier.js b/packages/graphile-build-pg/src/parseIdentifier.ts
similarity index 100%
rename from packages/graphile-build-pg/src/parseIdentifier.js
rename to packages/graphile-build-pg/src/parseIdentifier.ts
diff --git a/packages/graphile-build-pg/src/pgPrepareAndRun.js b/packages/graphile-build-pg/src/pgPrepareAndRun.ts
similarity index 97%
rename from packages/graphile-build-pg/src/pgPrepareAndRun.js
rename to packages/graphile-build-pg/src/pgPrepareAndRun.ts
index 5ab35dedc..cc1814a31 100644
--- a/packages/graphile-build-pg/src/pgPrepareAndRun.js
+++ b/packages/graphile-build-pg/src/pgPrepareAndRun.ts
@@ -1,7 +1,6 @@
-//@flow
 import { createHash } from "crypto";
 import LRU from "@graphile/lru";
-import type { PoolClient } from "pg";
+import { PoolClient } from "pg";
 
 const POSTGRAPHILE_PREPARED_STATEMENT_CACHE_SIZE =
   parseInt(process.env.POSTGRAPHILE_PREPARED_STATEMENT_CACHE_SIZE, 10) || 100;
diff --git a/packages/graphile-build-pg/src/plugins/PageInfoStartEndCursor.js b/packages/graphile-build-pg/src/plugins/PageInfoStartEndCursor.ts
similarity index 91%
rename from packages/graphile-build-pg/src/plugins/PageInfoStartEndCursor.js
rename to packages/graphile-build-pg/src/plugins/PageInfoStartEndCursor.ts
index 25ed0101c..9ee37c67f 100644
--- a/packages/graphile-build-pg/src/plugins/PageInfoStartEndCursor.js
+++ b/packages/graphile-build-pg/src/plugins/PageInfoStartEndCursor.ts
@@ -1,7 +1,6 @@
-// @flow
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 
-export default (function PageInfoStartEndCursor(builder) {
+export default function PageInfoStartEndCursor(builder) {
   builder.hook(
     "GraphQLObjectType:fields",
     (fields, build, context) => {
@@ -28,6 +27,7 @@ export default (function PageInfoStartEndCursor(builder) {
               isPageInfoStartCursorField: true,
             }
           ),
+
           endCursor: fieldWithHooks(
             "endCursor",
             ({ addDataGenerator }) => {
@@ -43,6 +43,7 @@ export default (function PageInfoStartEndCursor(builder) {
             }
           ),
         },
+
         `Adding startCursor/endCursor to ${Self.name}`
       );
     },
@@ -50,4 +51,4 @@ export default (function PageInfoStartEndCursor(builder) {
     [],
     ["Cursor"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgAllRows.js b/packages/graphile-build-pg/src/plugins/PgAllRows.ts
similarity index 98%
rename from packages/graphile-build-pg/src/plugins/PgAllRows.js
rename to packages/graphile-build-pg/src/plugins/PgAllRows.ts
index 372e5c5ca..c48ea739b 100644
--- a/packages/graphile-build-pg/src/plugins/PgAllRows.js
+++ b/packages/graphile-build-pg/src/plugins/PgAllRows.ts
@@ -1,9 +1,7 @@
-// @flow
-
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 import debugSql from "./debugSql";
 
-export default (async function PgAllRows(
+export default async function PgAllRows(
   builder,
   { pgViewUniqueKey, pgSimpleCollections, subscriptions }
 ) {
@@ -43,6 +41,7 @@ export default (async function PgAllRows(
             table.type.id,
             null
           );
+
           if (!TableType) {
             return memo;
           }
@@ -50,6 +49,7 @@ export default (async function PgAllRows(
           const ConnectionType = getTypeByName(
             inflection.connection(TableType.name)
           );
+
           if (!TableType) {
             throw new Error(
               `Could not find GraphQL type for table '${table.name}'`
@@ -98,11 +98,13 @@ export default (async function PgAllRows(
                     const parsedResolveInfoFragment = parseResolveInfo(
                       resolveInfo
                     );
+
                     parsedResolveInfoFragment.args = args; // Allow overriding via makeWrapResolversPlugin
                     const resolveData = getDataFromParsedResolveInfoFragment(
                       parsedResolveInfoFragment,
                       resolveInfo.returnType
                     );
+
                     let checkerGenerator;
                     const query = queryFromResolveData(
                       sqlFullTableName,
@@ -112,6 +114,7 @@ export default (async function PgAllRows(
                         useAsterisk: table.canUseAsterisk,
                         withPaginationAsFields: isConnection,
                       },
+
                       queryBuilder => {
                         if (subscriptions) {
                           queryBuilder.makeLiveCollection(
@@ -131,6 +134,7 @@ export default (async function PgAllRows(
                               queryBuilder.data.cursorPrefix = [
                                 "primary_key_asc",
                               ];
+
                               primaryKeys.forEach(key => {
                                 queryBuilder.orderBy(
                                   sql.fragment`${queryBuilder.getTableAlias()}.${sql.identifier(
@@ -148,12 +152,14 @@ export default (async function PgAllRows(
                               queryBuilder.data.cursorPrefix = [
                                 "view_unique_key_asc",
                               ];
+
                               queryBuilder.orderBy(
                                 sql.fragment`${queryBuilder.getTableAlias()}.${sql.identifier(
                                   uniqueIdAttribute.name
                                 )}`,
                                 true
                               );
+
                               queryBuilder.setOrderIsUnique();
                             }
                           });
@@ -162,6 +168,7 @@ export default (async function PgAllRows(
                       resolveContext,
                       resolveInfo.rootValue
                     );
+
                     const { text, values } = sql.compile(query);
                     if (debugSql.enabled) debugSql(text);
                     const result = await pgPrepareAndRun(
@@ -230,4 +237,4 @@ export default (async function PgAllRows(
     [],
     ["PgTables"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgBackwardRelationPlugin.js b/packages/graphile-build-pg/src/plugins/PgBackwardRelationPlugin.ts
similarity index 99%
rename from packages/graphile-build-pg/src/plugins/PgBackwardRelationPlugin.js
rename to packages/graphile-build-pg/src/plugins/PgBackwardRelationPlugin.ts
index da15452df..ca7e5fc2a 100644
--- a/packages/graphile-build-pg/src/plugins/PgBackwardRelationPlugin.js
+++ b/packages/graphile-build-pg/src/plugins/PgBackwardRelationPlugin.ts
@@ -1,7 +1,6 @@
-// @flow
 import debugFactory from "debug";
 
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 
 const debug = debugFactory("graphile-build-pg");
 
@@ -9,7 +8,7 @@ const OMIT = 0;
 const DEPRECATED = 1;
 const ONLY = 2;
 
-export default (function PgBackwardRelationPlugin(
+export default function PgBackwardRelationPlugin(
   builder,
   { pgLegacyRelations, pgSimpleCollections, subscriptions }
 ) {
@@ -49,17 +48,20 @@ export default (function PgBackwardRelationPlugin(
       const foreignKeyConstraints = foreignTable.foreignConstraints.filter(
         con => con.type === "f"
       );
+
       const foreignTableTypeName = inflection.tableType(foreignTable);
       const gqlForeignTableType = pgGetGqlTypeByTypeIdAndModifier(
         foreignTable.type.id,
         null
       );
+
       if (!gqlForeignTableType) {
         debug(
           `Could not determine type for foreign table with id ${
             foreignTable.type.id
           }`
         );
+
         return fields;
       }
 
@@ -80,10 +82,12 @@ export default (function PgBackwardRelationPlugin(
             table.type.id,
             null
           );
+
           if (!gqlTableType) {
             debug(
               `Could not determine type for table with id ${constraint.classId}`
             );
+
             return memo;
           }
           if (!table) {
@@ -159,6 +163,7 @@ export default (function PgBackwardRelationPlugin(
                               parsedResolveInfoFragment,
                               gqlTableType
                             );
+
                             const tableAlias = sql.identifier(Symbol());
                             const foreignTableAlias = queryBuilder.getTableAlias();
                             const query = queryFromResolveData(
@@ -171,6 +176,7 @@ export default (function PgBackwardRelationPlugin(
                                 addNullCase: true,
                                 withPagination: false,
                               },
+
                               innerQueryBuilder => {
                                 innerQueryBuilder.parentQueryBuilder = queryBuilder;
                                 if (
@@ -192,6 +198,7 @@ export default (function PgBackwardRelationPlugin(
                               queryBuilder.context,
                               queryBuilder.rootValue
                             );
+
                             return sql.fragment`(${query})`;
                           }, getSafeAliasFromAlias(parsedResolveInfoFragment.alias));
                         },
@@ -207,6 +214,7 @@ export default (function PgBackwardRelationPlugin(
                         const safeAlias = getSafeAliasFromResolveInfo(
                           resolveInfo
                         );
+
                         const record = data[safeAlias];
                         const liveRecord =
                           resolveInfo.rootValue &&
@@ -224,6 +232,7 @@ export default (function PgBackwardRelationPlugin(
                   }
                 ),
               },
+
               `Backward relation (single) for ${describePgEntity(
                 constraint
               )}. To rename this relation with smart comments:\n\n  ${sqlCommentByAddingTags(
@@ -270,6 +279,7 @@ export default (function PgBackwardRelationPlugin(
                         withPaginationAsFields: false,
                         asJsonAggregate: !isConnection,
                       };
+
                       addDataGenerator(parsedResolveInfoFragment => {
                         return {
                           pgQuery: queryBuilder => {
@@ -278,6 +288,7 @@ export default (function PgBackwardRelationPlugin(
                                 parsedResolveInfoFragment,
                                 isConnection ? ConnectionType : TableType
                               );
+
                               const tableAlias = sql.identifier(Symbol());
                               const foreignTableAlias = queryBuilder.getTableAlias();
                               const query = queryFromResolveData(
@@ -328,6 +339,7 @@ export default (function PgBackwardRelationPlugin(
                                           innerQueryBuilder.data.cursorPrefix = [
                                             "primary_key_asc",
                                           ];
+
                                           primaryKeys.forEach(key => {
                                             innerQueryBuilder.orderBy(
                                               sql.fragment`${innerQueryBuilder.getTableAlias()}.${sql.identifier(
@@ -355,6 +367,7 @@ export default (function PgBackwardRelationPlugin(
                                 queryBuilder.context,
                                 queryBuilder.rootValue
                               );
+
                               return sql.fragment`(${query})`;
                             }, getSafeAliasFromAlias(parsedResolveInfoFragment.alias));
                           },
@@ -363,10 +376,12 @@ export default (function PgBackwardRelationPlugin(
                       const ConnectionType = getTypeByName(
                         inflection.connection(gqlTableType.name)
                       );
+
                       const TableType = pgGetGqlTypeByTypeIdAndModifier(
                         table.type.id,
                         null
                       );
+
                       return {
                         description:
                           constraint.tags.backwardDescription ||
@@ -376,11 +391,13 @@ export default (function PgBackwardRelationPlugin(
                           : new GraphQLNonNull(
                               new GraphQLList(new GraphQLNonNull(TableType))
                             ),
+
                         args: {},
                         resolve: (data, _args, resolveContext, resolveInfo) => {
                           const safeAlias = getSafeAliasFromResolveInfo(
                             resolveInfo
                           );
+
                           const liveCollection =
                             resolveInfo.rootValue &&
                             resolveInfo.rootValue.liveCollection;
@@ -470,4 +487,4 @@ export default (function PgBackwardRelationPlugin(
     },
     ["PgBackwardRelation"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgBasicsPlugin.js b/packages/graphile-build-pg/src/plugins/PgBasicsPlugin.ts
similarity index 97%
rename from packages/graphile-build-pg/src/plugins/PgBasicsPlugin.js
rename to packages/graphile-build-pg/src/plugins/PgBasicsPlugin.ts
index b093824a3..b0cef25d5 100644
--- a/packages/graphile-build-pg/src/plugins/PgBasicsPlugin.js
+++ b/packages/graphile-build-pg/src/plugins/PgBasicsPlugin.ts
@@ -1,8 +1,7 @@
-// @flow
 import * as sql from "pg-sql2";
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 import { version } from "../../package.json";
-import type {
+import {
   PgProc,
   PgType,
   PgClass,
@@ -35,17 +34,16 @@ import pgPrepareAndRun from "../pgPrepareAndRun";
 
 const defaultPgColumnFilter = (_attr, _build, _context) => true;
 type Keys = Array<{
-  column: string,
-  table: string,
-  schema: ?string,
+  column: string;
+  table: string;
+  schema: string | null | undefined;
 }>;
 
 const identity = _ => _;
 
 export function preventEmptyResult<
-  // eslint-disable-next-line flowtype/no-weak-types
-  O: { [key: string]: (...args: Array<any>) => string }
->(obj: O): $ObjMap<O, <V>(V) => V> {
+  O extends { [key: string]: (...args: Array<any>) => string }
+>(obj: O): $ObjMap<O, <V>(a: V) => V> {
   return Object.keys(obj).reduce((memo, key) => {
     const fn = obj[key];
     memo[key] = function(...args) {
@@ -87,20 +85,20 @@ const omitWithRBACChecks = omit => (
     const tableEntity: PgClass = entity;
     if (
       (permission === READ || permission === ALL || permission === MANY) &&
-      (!tableEntity.aclSelectable &&
-        !tableEntity.attributes.some(attr => attr.aclSelectable))
+      !tableEntity.aclSelectable &&
+      !tableEntity.attributes.some(attr => attr.aclSelectable)
     ) {
       return true;
     } else if (
       permission === CREATE &&
-      (!tableEntity.aclInsertable &&
-        !tableEntity.attributes.some(attr => attr.aclInsertable))
+      !tableEntity.aclInsertable &&
+      !tableEntity.attributes.some(attr => attr.aclInsertable)
     ) {
       return true;
     } else if (
       permission === UPDATE &&
-      (!tableEntity.aclUpdatable &&
-        !tableEntity.attributes.some(attr => attr.aclUpdatable))
+      !tableEntity.aclUpdatable &&
+      !tableEntity.attributes.some(attr => attr.aclUpdatable)
     ) {
       return true;
     } else if (permission === DELETE && !tableEntity.aclDeletable) {
@@ -188,6 +186,7 @@ function describePgEntity(entity: PgEntity, includeAlias = true) {
           entity.tags,
           (value, key) => key === "name" || key.endsWith("Name")
         );
+
         if (Object.keys(tags).length) {
           return ` (with smart comments: ${chalk.bold(
             Object.keys(tags)
@@ -319,7 +318,7 @@ function sqlCommentByAddingTags(entity, tagsToAdd) {
   return `COMMENT ON ${sqlThing} IS ${commentValue};`;
 }
 
-export default (function PgBasicsPlugin(
+export default function PgBasicsPlugin(
   builder,
   {
     pgStrictFunctions = false,
@@ -446,7 +445,7 @@ export default (function PgBasicsPlugin(
           enumType(type: PgType) {
             return this.upperCamelCase(this._typeName(type));
           },
-          argument(name: ?string, index: number) {
+          argument(name: string | null | undefined, index: number) {
             return this.coerceToGraphQLName(
               this.camelCase(name || `arg${index}`)
             );
@@ -473,6 +472,7 @@ export default (function PgBasicsPlugin(
               proc,
               table
             );
+
             return this.orderByEnum(columnName, ascending);
           },
           domainType(type: PgType) {
@@ -873,9 +873,10 @@ export default (function PgBasicsPlugin(
             );
           },
         }),
+
         "Default inflectors from PgBasicsPlugin. You can override these with `makeAddInflectorsPlugin(..., true)`."
       );
     },
     ["PgBasics"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgColumnDeprecationPlugin.js b/packages/graphile-build-pg/src/plugins/PgColumnDeprecationPlugin.ts
similarity index 82%
rename from packages/graphile-build-pg/src/plugins/PgColumnDeprecationPlugin.js
rename to packages/graphile-build-pg/src/plugins/PgColumnDeprecationPlugin.ts
index d75d72767..a6198f7ac 100644
--- a/packages/graphile-build-pg/src/plugins/PgColumnDeprecationPlugin.js
+++ b/packages/graphile-build-pg/src/plugins/PgColumnDeprecationPlugin.ts
@@ -1,7 +1,6 @@
-// @flow
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 
-export default (function PgColumnDeprecationPlugin(builder) {
+export default function PgColumnDeprecationPlugin(builder) {
   builder.hook(
     "GraphQLObjectType:fields:field",
     (field, build, context) => {
@@ -24,4 +23,4 @@ export default (function PgColumnDeprecationPlugin(builder) {
     },
     ["PgColumnDeprecation"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgColumnsPlugin.js b/packages/graphile-build-pg/src/plugins/PgColumnsPlugin.ts
similarity index 98%
rename from packages/graphile-build-pg/src/plugins/PgColumnsPlugin.js
rename to packages/graphile-build-pg/src/plugins/PgColumnsPlugin.ts
index b640dd403..953526cd1 100644
--- a/packages/graphile-build-pg/src/plugins/PgColumnsPlugin.js
+++ b/packages/graphile-build-pg/src/plugins/PgColumnsPlugin.ts
@@ -1,10 +1,9 @@
-// @flow
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 
 const nullableIf = (GraphQLNonNull, condition, Type) =>
   condition ? Type : new GraphQLNonNull(Type);
 
-export default (function PgColumnsPlugin(builder) {
+export default function PgColumnsPlugin(builder) {
   builder.hook(
     "build",
     build => {
@@ -45,6 +44,7 @@ end
             parsedResolveInfoFragment,
             ReturnType
           );
+
           if (type.type === "c") {
             const isDefinitelyNotATable =
               type.class && !type.class.isSelectable;
@@ -58,6 +58,7 @@ end
                 addNotDistinctFromNullCase: isDefinitelyNotATable,
               }
             );
+
             return jsonBuildObject;
           } else {
             return pgTweakFragmentForTypeAndModifier(
@@ -148,6 +149,7 @@ end
                             type,
                             typeModifier
                           ),
+
                           fieldName
                         );
                       },
@@ -163,6 +165,7 @@ end
                         !attr.tags.notNull,
                       ReturnType
                     ),
+
                     resolve: (data, _args, _context, _resolveInfo) => {
                       return convertFromPg(data[fieldName]);
                     },
@@ -171,6 +174,7 @@ end
                 { pgFieldIntrospection: attr }
               ),
             },
+
             `Adding field for ${describePgEntity(
               attr
             )}. You can rename this field with:\n\n  ${sqlCommentByAddingTags(
@@ -180,6 +184,7 @@ end
               }
             )}`
           );
+
           return memo;
         }, {}),
         `Adding columns to '${describePgEntity(table)}'`
@@ -187,6 +192,7 @@ end
     },
     ["PgColumns"]
   );
+
   builder.hook(
     "GraphQLInputObjectType:fields",
     (fields, build, context) => {
@@ -209,6 +215,7 @@ end
           pgIntrospection: table,
           pgAddSubfield,
         },
+
         fieldWithHooks,
       } = context;
       if (
@@ -266,11 +273,14 @@ end
                       ) || GraphQLString
                     ),
                   },
+
                   attr.typeModifier
                 ),
+
                 { pgFieldIntrospection: attr }
               ),
             },
+
             `Adding input object field for ${describePgEntity(
               attr
             )}. You can rename this field with:\n\n  ${sqlCommentByAddingTags(
@@ -280,6 +290,7 @@ end
               }
             )}`
           );
+
           return memo;
         }, {}),
         `Adding columns to input object for ${describePgEntity(table)}`
@@ -287,4 +298,4 @@ end
     },
     ["PgColumns"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgComputedColumnsPlugin.js b/packages/graphile-build-pg/src/plugins/PgComputedColumnsPlugin.ts
similarity index 95%
rename from packages/graphile-build-pg/src/plugins/PgComputedColumnsPlugin.js
rename to packages/graphile-build-pg/src/plugins/PgComputedColumnsPlugin.ts
index ba9f2ca84..4ea6f6c5c 100644
--- a/packages/graphile-build-pg/src/plugins/PgComputedColumnsPlugin.js
+++ b/packages/graphile-build-pg/src/plugins/PgComputedColumnsPlugin.ts
@@ -1,6 +1,5 @@
-// @flow
-import type { Plugin, Build } from "graphile-build";
-import type { PgClass, PgProc } from "./PgIntrospectionPlugin";
+import { Plugin, Build } from "graphile-build";
+import { PgClass, PgProc } from "./PgIntrospectionPlugin";
 
 // This interface is not official yet, don't rely on it.
 export const getComputedColumnDetails = (
@@ -37,7 +36,7 @@ export const getComputedColumnDetails = (
   return { argTypes, pseudoColumnName };
 };
 
-export default (function PgComputedColumnsPlugin(
+export default function PgComputedColumnsPlugin(
   builder,
   { pgSimpleCollections }
 ) {
@@ -51,6 +50,7 @@ export default (function PgComputedColumnsPlugin(
           isInputType,
           pgIntrospection: table,
         },
+
         fieldWithHooks,
         Self,
       } = context;
@@ -88,6 +88,7 @@ export default (function PgComputedColumnsPlugin(
             table,
             proc
           );
+
           if (!computedColumnDetails) return memo;
           const { pseudoColumnName } = computedColumnDetails;
           function makeField(forceList) {
@@ -104,6 +105,7 @@ export default (function PgComputedColumnsPlugin(
                     forceList,
                   }),
                 },
+
                 `Adding computed column for ${describePgEntity(
                   proc
                 )}. You can rename this field with:\n\n  ${sqlCommentByAddingTags(
@@ -135,4 +137,4 @@ export default (function PgComputedColumnsPlugin(
     },
     ["PgComputedColumns"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgConditionComputedColumnPlugin.js b/packages/graphile-build-pg/src/plugins/PgConditionComputedColumnPlugin.ts
similarity index 97%
rename from packages/graphile-build-pg/src/plugins/PgConditionComputedColumnPlugin.js
rename to packages/graphile-build-pg/src/plugins/PgConditionComputedColumnPlugin.ts
index 8bdd1259e..ed96f16e0 100644
--- a/packages/graphile-build-pg/src/plugins/PgConditionComputedColumnPlugin.js
+++ b/packages/graphile-build-pg/src/plugins/PgConditionComputedColumnPlugin.ts
@@ -1,5 +1,4 @@
-// @flow
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 import { getComputedColumnDetails } from "./PgComputedColumnsPlugin";
 import assert from "assert";
 function getCompatibleComputedColumns(build, table) {
@@ -44,7 +43,7 @@ function getCompatibleComputedColumns(build, table) {
   }, []);
 }
 
-export default (function PgConditionComputedColumnPlugin(builder) {
+export default function PgConditionComputedColumnPlugin(builder) {
   builder.hook(
     "GraphQLInputObjectType:fields",
     (fields, build, context) => {
@@ -65,6 +64,7 @@ export default (function PgConditionComputedColumnPlugin(builder) {
         build,
         table
       );
+
       return extend(
         fields,
         compatibleComputedColumns.reduce((memo, { proc, pseudoColumnName }) => {
@@ -73,10 +73,12 @@ export default (function PgConditionComputedColumnPlugin(builder) {
             proc,
             table
           );
+
           const Type = pgGetGqlInputTypeByTypeIdAndModifier(
             proc.returnTypeId,
             null
           );
+
           if (!Type) return memo;
           memo = build.extend(
             memo,
@@ -87,16 +89,19 @@ export default (function PgConditionComputedColumnPlugin(builder) {
                   description: `Checks for equality with the object’s \`${fieldName}\` field.`,
                   type: Type,
                 },
+
                 {
                   isPgConnectionConditionInputField: true,
                   pgFieldIntrospection: proc,
                 }
               ),
             },
+
             `Adding computed column condition argument for ${describePgEntity(
               proc
             )}`
           );
+
           return memo;
         }, {})
       );
@@ -123,6 +128,7 @@ export default (function PgConditionComputedColumnPlugin(builder) {
           pgFieldIntrospection,
           pgFieldIntrospectionTable,
         },
+
         addArgDataGenerator,
       } = context;
 
@@ -152,6 +158,7 @@ export default (function PgConditionComputedColumnPlugin(builder) {
       const TableConditionType = getTypeByName(
         inflection.conditionType(TableType.name)
       );
+
       if (!TableConditionType) {
         return args;
       }
@@ -171,6 +178,7 @@ export default (function PgConditionComputedColumnPlugin(builder) {
           proc,
           table
         );
+
         const sqlFnName = sql.identifier(proc.namespaceName, proc.name);
         return {
           ...o,
@@ -208,4 +216,4 @@ export default (function PgConditionComputedColumnPlugin(builder) {
     },
     ["PgConditionComputedColumn"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgConnectionArgCondition.js b/packages/graphile-build-pg/src/plugins/PgConnectionArgCondition.ts
similarity index 97%
rename from packages/graphile-build-pg/src/plugins/PgConnectionArgCondition.js
rename to packages/graphile-build-pg/src/plugins/PgConnectionArgCondition.ts
index a52b5d7a9..8f0a19b5a 100644
--- a/packages/graphile-build-pg/src/plugins/PgConnectionArgCondition.js
+++ b/packages/graphile-build-pg/src/plugins/PgConnectionArgCondition.ts
@@ -1,7 +1,6 @@
-// @flow
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 
-export default (function PgConnectionArgCondition(builder) {
+export default function PgConnectionArgCondition(builder) {
   builder.hook(
     "init",
     (_, build) => {
@@ -49,17 +48,21 @@ export default (function PgConnectionArgCondition(builder) {
                             attr.typeModifier
                           ) || GraphQLString,
                       },
+
                       {
                         isPgConnectionConditionInputField: true,
                       }
                     ),
                   },
+
                   `Adding condition argument for ${describePgEntity(attr)}`
                 );
+
                 return memo;
               }, {});
             },
           },
+
           {
             __origin: `Adding condition type for ${describePgEntity(
               table
@@ -72,6 +75,7 @@ export default (function PgConnectionArgCondition(builder) {
             pgIntrospection: table,
             isPgCondition: true,
           },
+
           true // Conditions might all be filtered
         );
       });
@@ -103,6 +107,7 @@ export default (function PgConnectionArgCondition(builder) {
           pgFieldIntrospection,
           pgFieldIntrospectionTable,
         },
+
         addArgDataGenerator,
         Self,
       } = context;
@@ -137,6 +142,7 @@ export default (function PgConnectionArgCondition(builder) {
       const TableConditionType = getTypeByName(
         inflection.conditionType(TableType.name)
       );
+
       if (!TableConditionType) {
         return args;
       }
@@ -156,6 +162,7 @@ export default (function PgConnectionArgCondition(builder) {
                   queryBuilder.addLiveCondition(() => record =>
                     record[attr.name] === val
                   );
+
                   queryBuilder.where(
                     sql.fragment`${queryBuilder.getTableAlias()}.${sql.identifier(
                       attr.name
@@ -165,6 +172,7 @@ export default (function PgConnectionArgCondition(builder) {
                   queryBuilder.addLiveCondition(() => record =>
                     record[attr.name] == null
                   );
+
                   queryBuilder.where(
                     sql.fragment`${queryBuilder.getTableAlias()}.${sql.identifier(
                       attr.name
@@ -186,9 +194,10 @@ export default (function PgConnectionArgCondition(builder) {
             type: TableConditionType,
           },
         },
+
         `Adding condition to connection field '${fieldName}' of '${Self.name}'`
       );
     },
     ["PgConnectionArgCondition"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgConnectionArgFirstLastBeforeAfter.js b/packages/graphile-build-pg/src/plugins/PgConnectionArgFirstLastBeforeAfter.ts
similarity index 96%
rename from packages/graphile-build-pg/src/plugins/PgConnectionArgFirstLastBeforeAfter.js
rename to packages/graphile-build-pg/src/plugins/PgConnectionArgFirstLastBeforeAfter.ts
index c8d73499b..268e0e6f5 100644
--- a/packages/graphile-build-pg/src/plugins/PgConnectionArgFirstLastBeforeAfter.js
+++ b/packages/graphile-build-pg/src/plugins/PgConnectionArgFirstLastBeforeAfter.ts
@@ -1,9 +1,8 @@
-// @flow
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 
 const base64Decode = str => Buffer.from(String(str), "base64").toString("utf8");
 
-export default (function PgConnectionArgs(builder) {
+export default function PgConnectionArgs(builder) {
   builder.hook(
     "GraphQLObjectType:fields:field:args",
     (args, build, context) => {
@@ -19,6 +18,7 @@ export default (function PgConnectionArgs(builder) {
           isPgFieldSimpleCollection,
           pgFieldIntrospection: source,
         },
+
         addArgDataGenerator,
         Self,
       } = context;
@@ -90,6 +90,7 @@ export default (function PgConnectionArgs(builder) {
             description: "Only read the first `n` values of the set.",
             type: GraphQLInt,
           },
+
           ...(isPgFieldConnection
             ? {
                 last: {
@@ -104,6 +105,7 @@ export default (function PgConnectionArgs(builder) {
               : "Skip the first `n` values.",
             type: GraphQLInt,
           },
+
           ...(isPgFieldConnection
             ? {
                 before: {
@@ -111,6 +113,7 @@ export default (function PgConnectionArgs(builder) {
                     "Read all values in the set before (above) this cursor.",
                   type: Cursor,
                 },
+
                 after: {
                   description:
                     "Read all values in the set after (below) this cursor.",
@@ -119,6 +122,7 @@ export default (function PgConnectionArgs(builder) {
               }
             : null),
         },
+
         isPgFieldConnection
           ? `Adding connection pagination args to field '${fieldName}' of '${
               Self.name
@@ -130,4 +134,4 @@ export default (function PgConnectionArgs(builder) {
     },
     ["PgConnectionArgFirstLastBeforeAfter"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgConnectionArgOrderBy.js b/packages/graphile-build-pg/src/plugins/PgConnectionArgOrderBy.ts
similarity index 97%
rename from packages/graphile-build-pg/src/plugins/PgConnectionArgOrderBy.js
rename to packages/graphile-build-pg/src/plugins/PgConnectionArgOrderBy.ts
index 1cb7c857a..debe39d75 100644
--- a/packages/graphile-build-pg/src/plugins/PgConnectionArgOrderBy.js
+++ b/packages/graphile-build-pg/src/plugins/PgConnectionArgOrderBy.ts
@@ -1,8 +1,7 @@
-// @flow
 import isString from "lodash/isString";
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 
-export default (function PgConnectionArgOrderBy(builder, { orderByNullsLast }) {
+export default function PgConnectionArgOrderBy(builder, { orderByNullsLast }) {
   builder.hook(
     "init",
     (_, build) => {
@@ -36,6 +35,7 @@ export default (function PgConnectionArgOrderBy(builder, { orderByNullsLast }) {
               },
             },
           },
+
           {
             __origin: `Adding connection "orderBy" argument for ${describePgEntity(
               table
@@ -75,6 +75,7 @@ export default (function PgConnectionArgOrderBy(builder, { orderByNullsLast }) {
           pgFieldIntrospection,
           pgFieldIntrospectionTable,
         },
+
         addArgDataGenerator,
         Self,
       } = context;
@@ -109,6 +110,7 @@ export default (function PgConnectionArgOrderBy(builder, { orderByNullsLast }) {
       const TableOrderByType = getTypeByName(
         inflection.orderByType(tableTypeName)
       );
+
       const cursorPrefixFromOrderBy = orderBy => {
         if (orderBy) {
           let cursorPrefixes = [];
@@ -178,9 +180,10 @@ export default (function PgConnectionArgOrderBy(builder, { orderByNullsLast }) {
             type: new GraphQLList(new GraphQLNonNull(TableOrderByType)),
           },
         },
+
         `Adding 'orderBy' argument to field '${fieldName}' of '${Self.name}'`
       );
     },
     ["PgConnectionArgOrderBy"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgConnectionArgOrderByDefaultValue.js b/packages/graphile-build-pg/src/plugins/PgConnectionArgOrderByDefaultValue.ts
similarity index 90%
rename from packages/graphile-build-pg/src/plugins/PgConnectionArgOrderByDefaultValue.js
rename to packages/graphile-build-pg/src/plugins/PgConnectionArgOrderByDefaultValue.ts
index 90e523bdd..8f435e85c 100644
--- a/packages/graphile-build-pg/src/plugins/PgConnectionArgOrderByDefaultValue.js
+++ b/packages/graphile-build-pg/src/plugins/PgConnectionArgOrderByDefaultValue.ts
@@ -1,7 +1,6 @@
-// @flow
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 
-export default (function PgConnectionArgOrderByDefaultValue(builder) {
+export default function PgConnectionArgOrderByDefaultValue(builder) {
   builder.hook(
     "GraphQLObjectType:fields:field:args",
     (args, build, context) => {
@@ -31,6 +30,7 @@ export default (function PgConnectionArgOrderByDefaultValue(builder) {
       const TableOrderByType = getTypeByName(
         inflection.orderByType(tableTypeName)
       );
+
       if (!TableOrderByType) {
         return args;
       }
@@ -45,6 +45,7 @@ export default (function PgConnectionArgOrderByDefaultValue(builder) {
           {
             defaultValue: defaultValueEnum && [defaultValueEnum.value],
           },
+
           `Adding defaultValue to orderBy for field '${fieldName}' of '${
             Self.name
           }'`
@@ -53,4 +54,4 @@ export default (function PgConnectionArgOrderByDefaultValue(builder) {
     },
     ["PgConnectionArgOrderByDefaultValue"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgConnectionTotalCount.js b/packages/graphile-build-pg/src/plugins/PgConnectionTotalCount.ts
similarity index 93%
rename from packages/graphile-build-pg/src/plugins/PgConnectionTotalCount.js
rename to packages/graphile-build-pg/src/plugins/PgConnectionTotalCount.ts
index 049b24823..6b2a005ef 100644
--- a/packages/graphile-build-pg/src/plugins/PgConnectionTotalCount.js
+++ b/packages/graphile-build-pg/src/plugins/PgConnectionTotalCount.ts
@@ -1,7 +1,6 @@
-// @flow
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 
-export default (function PgConnectionTotalCount(builder) {
+export default function PgConnectionTotalCount(builder) {
   builder.hook(
     "GraphQLObjectType:fields",
     (fields, build, context) => {
@@ -58,9 +57,10 @@ export default (function PgConnectionTotalCount(builder) {
             }
           ),
         },
+
         `Adding totalCount to connection '${Self.name}'`
       );
     },
     ["PgConnectionTotalCount"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgForwardRelationPlugin.js b/packages/graphile-build-pg/src/plugins/PgForwardRelationPlugin.ts
similarity index 98%
rename from packages/graphile-build-pg/src/plugins/PgForwardRelationPlugin.js
rename to packages/graphile-build-pg/src/plugins/PgForwardRelationPlugin.ts
index f063749ec..ba83f53d5 100644
--- a/packages/graphile-build-pg/src/plugins/PgForwardRelationPlugin.js
+++ b/packages/graphile-build-pg/src/plugins/PgForwardRelationPlugin.ts
@@ -1,10 +1,9 @@
-// @flow
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 import debugFactory from "debug";
 
 const debug = debugFactory("graphile-build-pg");
 
-export default (function PgForwardRelationPlugin(builder, { subscriptions }) {
+export default function PgForwardRelationPlugin(builder, { subscriptions }) {
   builder.hook(
     "GraphQLObjectType:fields",
     (fields, build, context) => {
@@ -29,6 +28,7 @@ export default (function PgForwardRelationPlugin(builder, { subscriptions }) {
           pgIntrospection,
           pgIntrospectionTable,
         },
+
         fieldWithHooks,
         Self,
       } = context;
@@ -66,11 +66,13 @@ export default (function PgForwardRelationPlugin(builder, { subscriptions }) {
             table.type.id,
             null
           );
+
           const tableTypeName = gqlTableType.name;
           if (!gqlTableType) {
             debug(
               `Could not determine type for table with id ${constraint.classId}`
             );
+
             return memo;
           }
           const foreignTable =
@@ -79,6 +81,7 @@ export default (function PgForwardRelationPlugin(builder, { subscriptions }) {
             foreignTable.type.id,
             null
           );
+
           const foreignTableTypeName = gqlForeignTableType.name;
           if (!gqlForeignTableType) {
             debug(
@@ -86,6 +89,7 @@ export default (function PgForwardRelationPlugin(builder, { subscriptions }) {
                 constraint.foreignClassId
               }`
             );
+
             return memo;
           }
           if (!foreignTable) {
@@ -136,18 +140,21 @@ export default (function PgForwardRelationPlugin(builder, { subscriptions }) {
                             parsedResolveInfoFragment,
                             gqlForeignTableType
                           );
+
                           const foreignTableAlias = sql.identifier(Symbol());
                           const query = queryFromResolveData(
                             sql.identifier(
                               foreignSchema.name,
                               foreignTable.name
                             ),
+
                             foreignTableAlias,
                             resolveData,
                             {
                               useAsterisk: false, // Because it's only a single relation, no need
                               asJson: true,
                             },
+
                             innerQueryBuilder => {
                               innerQueryBuilder.parentQueryBuilder = queryBuilder;
                               if (subscriptions && table.primaryKeyConstraint) {
@@ -174,6 +181,7 @@ export default (function PgForwardRelationPlugin(builder, { subscriptions }) {
                             queryBuilder.context,
                             queryBuilder.rootValue
                           );
+
                           return sql.fragment`(${query})`;
                         }, getSafeAliasFromAlias(parsedResolveInfoFragment.alias));
                       },
@@ -190,6 +198,7 @@ export default (function PgForwardRelationPlugin(builder, { subscriptions }) {
                       const safeAlias = getSafeAliasFromResolveInfo(
                         resolveInfo
                       );
+
                       const record = data[safeAlias];
                       const liveRecord =
                         resolveInfo.rootValue &&
@@ -207,6 +216,7 @@ export default (function PgForwardRelationPlugin(builder, { subscriptions }) {
                 }
               ),
             },
+
             `Forward relation for ${describePgEntity(
               constraint
             )}. To rename this relation with smart comments:\n\n  ${sqlCommentByAddingTags(
@@ -216,6 +226,7 @@ export default (function PgForwardRelationPlugin(builder, { subscriptions }) {
               }
             )}`
           );
+
           return memo;
         }, {}),
         `Adding forward relations to '${Self.name}'`
@@ -223,4 +234,4 @@ export default (function PgForwardRelationPlugin(builder, { subscriptions }) {
     },
     ["PgForwardRelation"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgIntrospectionPlugin.js b/packages/graphile-build-pg/src/plugins/PgIntrospectionPlugin.ts
similarity index 85%
rename from packages/graphile-build-pg/src/plugins/PgIntrospectionPlugin.js
rename to packages/graphile-build-pg/src/plugins/PgIntrospectionPlugin.ts
index b65d12e10..d969f2545 100644
--- a/packages/graphile-build-pg/src/plugins/PgIntrospectionPlugin.js
+++ b/packages/graphile-build-pg/src/plugins/PgIntrospectionPlugin.ts
@@ -1,6 +1,5 @@
-// @flow
-import type { Plugin } from "graphile-build";
-import type { Client } from "pg";
+import { Plugin } from "graphile-build";
+import { Client } from "pg";
 import withPgClient, {
   getPgClientAndReleaserFromConfig,
 } from "../withPgClient";
@@ -21,172 +20,172 @@ const WATCH_FIXTURES_PATH = `${__dirname}/../../res/watch-fixtures.sql`;
 // Ref: https://github.com/graphile/postgraphile/tree/master/src/postgres/introspection/object
 
 export type PgNamespace = {
-  kind: "namespace",
-  id: string,
-  name: string,
-  comment: ?string,
-  description: ?string,
-  tags: { [string]: string },
+  kind: "namespace";
+  id: string;
+  name: string;
+  comment: string | null | undefined;
+  description: string | null | undefined;
+  tags: { [a: string]: string };
 };
 
 export type PgProc = {
-  kind: "procedure",
-  id: string,
-  name: string,
-  comment: ?string,
-  description: ?string,
-  namespaceId: string,
-  namespaceName: string,
-  isStrict: boolean,
-  returnsSet: boolean,
-  isStable: boolean,
-  returnTypeId: string,
-  argTypeIds: Array<string>,
-  argNames: Array<string>,
-  argModes: Array<"i" | "o" | "b" | "v" | "t">,
-  inputArgsCount: number,
-  argDefaultsNum: number,
-  namespace: PgNamespace,
-  tags: { [string]: string },
-  cost: number,
-  aclExecutable: boolean,
-  language: string,
+  kind: "procedure";
+  id: string;
+  name: string;
+  comment: string | null | undefined;
+  description: string | null | undefined;
+  namespaceId: string;
+  namespaceName: string;
+  isStrict: boolean;
+  returnsSet: boolean;
+  isStable: boolean;
+  returnTypeId: string;
+  argTypeIds: Array<string>;
+  argNames: Array<string>;
+  argModes: Array<"i" | "o" | "b" | "v" | "t">;
+  inputArgsCount: number;
+  argDefaultsNum: number;
+  namespace: PgNamespace;
+  tags: { [a: string]: string };
+  cost: number;
+  aclExecutable: boolean;
+  language: string;
 };
 
 export type PgClass = {
-  kind: "class",
-  id: string,
-  name: string,
-  comment: ?string,
-  description: ?string,
-  classKind: string,
-  namespaceId: string,
-  namespaceName: string,
-  typeId: string,
-  isSelectable: boolean,
-  isInsertable: boolean,
-  isUpdatable: boolean,
-  isDeletable: boolean,
-  isExtensionConfigurationTable: boolean,
-  namespace: PgNamespace,
-  type: PgType,
-  tags: { [string]: string },
-  attributes: [PgAttribute],
-  constraints: [PgConstraint],
-  foreignConstraints: [PgConstraint],
-  primaryKeyConstraint: ?PgConstraint,
-  aclSelectable: boolean,
-  aclInsertable: boolean,
-  aclUpdatable: boolean,
-  aclDeletable: boolean,
-  canUseAsterisk: boolean,
+  kind: "class";
+  id: string;
+  name: string;
+  comment: string | null | undefined;
+  description: string | null | undefined;
+  classKind: string;
+  namespaceId: string;
+  namespaceName: string;
+  typeId: string;
+  isSelectable: boolean;
+  isInsertable: boolean;
+  isUpdatable: boolean;
+  isDeletable: boolean;
+  isExtensionConfigurationTable: boolean;
+  namespace: PgNamespace;
+  type: PgType;
+  tags: { [a: string]: string };
+  attributes: [PgAttribute];
+  constraints: [PgConstraint];
+  foreignConstraints: [PgConstraint];
+  primaryKeyConstraint: PgConstraint | null | undefined;
+  aclSelectable: boolean;
+  aclInsertable: boolean;
+  aclUpdatable: boolean;
+  aclDeletable: boolean;
+  canUseAsterisk: boolean;
 };
 
 export type PgType = {
-  kind: "type",
-  id: string,
-  name: string,
-  comment: ?string,
-  description: ?string,
-  namespaceId: string,
-  namespaceName: string,
-  type: string,
-  category: string,
-  domainIsNotNull: boolean,
-  arrayItemTypeId: ?string,
-  arrayItemType: ?PgType,
-  arrayType: ?PgType,
-  typeLength: ?number,
-  isPgArray: boolean,
-  classId: ?string,
-  class: ?PgClass,
-  domainBaseTypeId: ?string,
-  domainBaseType: ?PgType,
-  domainTypeModifier: ?number,
-  tags: { [string]: string },
+  kind: "type";
+  id: string;
+  name: string;
+  comment: string | null | undefined;
+  description: string | null | undefined;
+  namespaceId: string;
+  namespaceName: string;
+  type: string;
+  category: string;
+  domainIsNotNull: boolean;
+  arrayItemTypeId: string | null | undefined;
+  arrayItemType: PgType | null | undefined;
+  arrayType: PgType | null | undefined;
+  typeLength: number | null | undefined;
+  isPgArray: boolean;
+  classId: string | null | undefined;
+  class: PgClass | null | undefined;
+  domainBaseTypeId: string | null | undefined;
+  domainBaseType: PgType | null | undefined;
+  domainTypeModifier: number | null | undefined;
+  tags: { [a: string]: string };
 };
 
 export type PgAttribute = {
-  kind: "attribute",
-  classId: string,
-  num: number,
-  name: string,
-  comment: ?string,
-  description: ?string,
-  typeId: string,
-  typeModifier: number,
-  isNotNull: boolean,
-  hasDefault: boolean,
-  identity: "" | "a" | "d",
-  class: PgClass,
-  type: PgType,
-  namespace: PgNamespace,
-  tags: { [string]: string },
-  aclSelectable: boolean,
-  aclInsertable: boolean,
-  aclUpdatable: boolean,
-  isIndexed: ?boolean,
-  isUnique: ?boolean,
-  columnLevelSelectGrant: boolean,
+  kind: "attribute";
+  classId: string;
+  num: number;
+  name: string;
+  comment: string | null | undefined;
+  description: string | null | undefined;
+  typeId: string;
+  typeModifier: number;
+  isNotNull: boolean;
+  hasDefault: boolean;
+  identity: "" | "a" | "d";
+  class: PgClass;
+  type: PgType;
+  namespace: PgNamespace;
+  tags: { [a: string]: string };
+  aclSelectable: boolean;
+  aclInsertable: boolean;
+  aclUpdatable: boolean;
+  isIndexed: boolean | null | undefined;
+  isUnique: boolean | null | undefined;
+  columnLevelSelectGrant: boolean;
 };
 
 export type PgConstraint = {
-  kind: "constraint",
-  id: string,
-  name: string,
-  type: string,
-  classId: string,
-  class: PgClass,
-  foreignClassId: ?string,
-  foreignClass: ?PgClass,
-  comment: ?string,
-  description: ?string,
-  keyAttributeNums: Array<number>,
-  keyAttributes: [PgAttribute],
-  foreignKeyAttributeNums: Array<number>,
-  foreignKeyAttributes: [PgAttribute],
-  namespace: PgNamespace,
-  isIndexed: ?boolean,
-  tags: { [string]: string },
+  kind: "constraint";
+  id: string;
+  name: string;
+  type: string;
+  classId: string;
+  class: PgClass;
+  foreignClassId: string | null | undefined;
+  foreignClass: PgClass | null | undefined;
+  comment: string | null | undefined;
+  description: string | null | undefined;
+  keyAttributeNums: Array<number>;
+  keyAttributes: [PgAttribute];
+  foreignKeyAttributeNums: Array<number>;
+  foreignKeyAttributes: [PgAttribute];
+  namespace: PgNamespace;
+  isIndexed: boolean | null | undefined;
+  tags: { [a: string]: string };
 };
 
 export type PgExtension = {
-  kind: "extension",
-  id: string,
-  name: string,
-  namespaceId: string,
-  namespaceName: string,
-  relocatable: boolean,
-  version: string,
-  configurationClassIds?: Array<string>,
-  comment: ?string,
-  description: ?string,
-  tags: { [string]: string },
+  kind: "extension";
+  id: string;
+  name: string;
+  namespaceId: string;
+  namespaceName: string;
+  relocatable: boolean;
+  version: string;
+  configurationClassIds?: Array<string>;
+  comment: string | null | undefined;
+  description: string | null | undefined;
+  tags: { [a: string]: string };
 };
 
 export type PgIndex = {
-  kind: "index",
-  id: string,
-  name: string,
-  namespaceName: string,
-  classId: string,
-  numberOfAttributes: number,
-  indexType: string,
-  isUnique: boolean,
-  isPrimary: boolean,
+  kind: "index";
+  id: string;
+  name: string;
+  namespaceName: string;
+  classId: string;
+  numberOfAttributes: number;
+  indexType: string;
+  isUnique: boolean;
+  isPrimary: boolean;
   /*
-  Though these exist, we don't want to officially
-  support them yet.
-
-  isImmediate: boolean,
-  isReplicaIdentity: boolean,
-  isValid: boolean,
-  */
-  attributeNums: Array<number>,
-  attributePropertiesAsc: ?Array<boolean>,
-  attributePropertiesNullsFirst: ?Array<boolean>,
-  description: ?string,
-  tags: { [string]: string },
+                      Though these exist, we don't want to officially
+                      support them yet.
+                       isImmediate: boolean,
+                      isReplicaIdentity: boolean,
+                      isValid: boolean,
+                      */
+
+  attributeNums: Array<number>;
+  attributePropertiesAsc: Array<boolean> | null | undefined;
+  attributePropertiesNullsFirst: Array<boolean> | null | undefined;
+  description: string | null | undefined;
+  tags: { [a: string]: string };
 };
 
 export type PgEntity =
@@ -251,6 +250,7 @@ function smartCommentConstraints(introspectionResults) {
       const pk = introspectionResults.constraint.find(
         c => c.classId == tbl.id && c.type === "p"
       );
+
       if (pk) {
         return pk.keyAttributeNums.map(n => attributes.find(a => a.num === n));
       } else {
@@ -279,6 +279,7 @@ function smartCommentConstraints(introspectionResults) {
     const namespace = introspectionResults.namespace.find(
       n => n.id === klass.namespaceId
     );
+
     if (!namespace) {
       return;
     }
@@ -293,6 +294,7 @@ function smartCommentConstraints(introspectionResults) {
       const { spec: pkSpec, tags, description } = parseConstraintSpec(
         klass.tags.primaryKey
       );
+
       // $FlowFixMe
       const columns: string[] = parseSqlColumn(pkSpec, true);
       const attributes = attributesByNames(
@@ -300,6 +302,7 @@ function smartCommentConstraints(introspectionResults) {
         columns,
         `@primaryKey ${klass.tags.primaryKey}`
       );
+
       attributes.forEach(attr => {
         attr.tags.notNull = true;
       });
@@ -320,6 +323,7 @@ function smartCommentConstraints(introspectionResults) {
         foreignKeyAttributeNums: null,
         tags,
       };
+
       introspectionResults.constraint.push(fakeConstraint);
     }
   });
@@ -328,6 +332,7 @@ function smartCommentConstraints(introspectionResults) {
     const namespace = introspectionResults.namespace.find(
       n => n.id === klass.namespaceId
     );
+
     if (!namespace) {
       return;
     }
@@ -355,9 +360,11 @@ function smartCommentConstraints(introspectionResults) {
         const { spec: fkSpec, tags, description } = parseConstraintSpec(
           fkSpecRaw
         );
+
         const matches = fkSpec.match(
           /^\(([^()]+)\) references ([^().]+)(?:\.([^().]+))?(?:\s*\(([^()]+)\))?$/i
         );
+
         if (!matches) {
           throw new Error(
             `Invalid foreignKey syntax for '${klass.namespaceName}.${
@@ -390,6 +397,7 @@ function smartCommentConstraints(introspectionResults) {
         const foreignKlass = introspectionResults.class.find(
           k => k.name === foreignTable && k.namespaceName === foreignSchema
         );
+
         if (!foreignKlass) {
           throw new Error(
             `@foreignKey smart comment referenced non-existant table/view '${foreignSchema}'.'${foreignTable}'. Note that this reference must use *database names* (i.e. it does not respect @name). (${fkSpecRaw})`
@@ -398,6 +406,7 @@ function smartCommentConstraints(introspectionResults) {
         const foreignNamespace = introspectionResults.namespace.find(
           n => n.id === foreignKlass.namespaceId
         );
+
         if (!foreignNamespace) {
           return;
         }
@@ -429,13 +438,14 @@ function smartCommentConstraints(introspectionResults) {
           foreignKeyAttributeNums,
           tags,
         };
+
         introspectionResults.constraint.push(fakeConstraint);
       });
     }
   });
 }
 
-export default (async function PgIntrospectionPlugin(
+export default async function PgIntrospectionPlugin(
   builder,
   {
     pgConfig,
@@ -474,13 +484,16 @@ export default (async function PgIntrospectionPlugin(
           const versionResult = await pgClient.query(
             "show server_version_num;"
           );
+
           const serverVersionNum = parseInt(
             versionResult.rows[0].server_version_num,
             10
           );
+
           const introspectionQuery = makeIntrospectionQuery(serverVersionNum, {
             pgLegacyFunctionsOnly,
           });
+
           const { rows } = await pgClient.query(introspectionQuery, [
             schemas,
             pgIncludeExtensionResources,
@@ -497,6 +510,7 @@ export default (async function PgIntrospectionPlugin(
             extension: [],
             index: [],
           };
+
           for (const { object } of rows) {
             result[object.kind].push(object);
           }
@@ -529,6 +543,7 @@ export default (async function PgIntrospectionPlugin(
             result.extension,
             e => e.configurationClassIds
           );
+
           result.class.forEach(klass => {
             klass.isExtensionConfigurationTable =
               extensionConfigurationClassIds.indexOf(klass.id) >= 0;
@@ -582,19 +597,23 @@ export default (async function PgIntrospectionPlugin(
       introspectionResultsByKind.namespace,
       "id"
     );
+
     introspectionResultsByKind.classById = xByY(
       introspectionResultsByKind.class,
       "id"
     );
+
     introspectionResultsByKind.typeById = xByY(
       introspectionResultsByKind.type,
       "id"
     );
+
     introspectionResultsByKind.attributeByClassIdAndNum = xByYAndZ(
       introspectionResultsByKind.attribute,
       "classId",
       "num"
     );
+
     introspectionResultsByKind.extensionById = xByY(
       introspectionResultsByKind.extension,
       "id"
@@ -749,15 +768,19 @@ export default (async function PgIntrospectionPlugin(
       klass.attributes = introspectionResultsByKind.attribute.filter(
         attr => attr.classId === klass.id
       );
+
       klass.canUseAsterisk = !klass.attributes.some(
         attr => attr.columnLevelSelectGrant
       );
+
       klass.constraints = introspectionResultsByKind.constraint.filter(
         constraint => constraint.classId === klass.id
       );
+
       klass.foreignConstraints = introspectionResultsByKind.constraint.filter(
         constraint => constraint.foreignClassId === klass.id
       );
+
       klass.primaryKeyConstraint = klass.constraints.find(
         constraint => constraint.type === "p"
       );
@@ -818,10 +841,10 @@ export default (async function PgIntrospectionPlugin(
   let listener;
 
   class Listener {
-    _handleChange: () => void;
+    _handleChange: () => undefined;
     client: Client | null;
     stopped: boolean;
-    _reallyReleaseClient: (() => Promise<void>) | null;
+    _reallyReleaseClient: (() => Promise<undefined>) | null;
     _haveDisplayedError: boolean;
     constructor(triggerRebuild) {
       this.stopped = false;
@@ -843,6 +866,7 @@ export default (async function PgIntrospectionPlugin(
           trailing: true,
         }
       );
+
       this._listener = this._listener.bind(this);
       this._handleClientError = this._handleClientError.bind(this);
       this._start();
@@ -887,16 +911,19 @@ export default (async function PgIntrospectionPlugin(
                         "Failed to setup watch fixtures in Postgres database"
                       )} ️️⚠️`
                     );
+
                     console.warn(
                       chalk.yellow(
                         "This is likely because the PostgreSQL user in the connection string does not have sufficient privileges; you can solve this by passing the 'owner' connection string via '--owner-connection' / 'ownerConnectionString'. If the fixtures already exist, the watch functionality may still work."
                       )
                     );
+
                     console.warn(
                       chalk.yellow(
                         "Enable DEBUG='graphile-build-pg' to see the error"
                       )
                     );
+
                     /* eslint-enable no-console */
                   }
                   debug(error);
@@ -916,7 +943,7 @@ export default (async function PgIntrospectionPlugin(
       }
     }
 
-    _handleClientError: (e: Error) => void;
+    _handleClientError: (e: Error) => undefined;
     _handleClientError(e) {
       // Client is already cleaned up
       this.client = null;
@@ -932,6 +959,7 @@ export default (async function PgIntrospectionPlugin(
         "Error occurred for PG watching client; reconnecting in 2 seconds.",
         e.message
       );
+
       await this._releaseClient();
       setTimeout(() => {
         if (!this.stopped) {
@@ -942,7 +970,7 @@ export default (async function PgIntrospectionPlugin(
     }
 
     // eslint-disable-next-line flowtype/no-weak-types
-    _listener: (notification: any) => void;
+    _listener: (notification: any) => undefined;
     // eslint-disable-next-line flowtype/no-weak-types
     async _listener(notification: any) {
       if (notification.channel !== "postgraphile_watch") {
@@ -964,6 +992,7 @@ export default (async function PgIntrospectionPlugin(
           const affectsOurSchemas = payload.payload.some(
             schemaName => schemas.indexOf(schemaName) >= 0
           );
+
           if (affectsOurSchemas) {
             this._handleChange();
           }
@@ -1036,4 +1065,4 @@ export default (async function PgIntrospectionPlugin(
     [],
     ["PgBasics"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgJWTPlugin.js b/packages/graphile-build-pg/src/plugins/PgJWTPlugin.ts
similarity index 97%
rename from packages/graphile-build-pg/src/plugins/PgJWTPlugin.js
rename to packages/graphile-build-pg/src/plugins/PgJWTPlugin.ts
index 3f1313195..753734b1d 100644
--- a/packages/graphile-build-pg/src/plugins/PgJWTPlugin.js
+++ b/packages/graphile-build-pg/src/plugins/PgJWTPlugin.ts
@@ -1,8 +1,7 @@
-// @flow
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 import { sign as signJwt } from "jsonwebtoken";
 
-export default (function PgJWTPlugin(
+export default function PgJWTPlugin(
   builder,
   { pgJwtTypeIdentifier, pgJwtSecret, pgJwtSignOptions }
 ) {
@@ -44,6 +43,7 @@ export default (function PgJWTPlugin(
           table.name === typeName &&
           table.namespaceName === namespaceName
       );
+
       if (!compositeClass) {
         throw new Error(
           `Could not find JWT type '"${namespaceName}"."${typeName}"'`
@@ -84,11 +84,13 @@ export default (function PgJWTPlugin(
                     : {
                         audience: "postgraphile",
                       },
+
                   token.iss || (pgJwtSignOptions && pgJwtSignOptions.issuer)
                     ? null
                     : {
                         issuer: "postgraphile",
                       },
+
                   token.exp || (pgJwtSignOptions && pgJwtSignOptions.expiresIn)
                     ? null
                     : {
@@ -98,6 +100,7 @@ export default (function PgJWTPlugin(
               );
             },
           },
+
           {
             __origin: `Adding JWT type based on ${describePgEntity(
               compositeType
@@ -105,6 +108,7 @@ export default (function PgJWTPlugin(
             isPgJwtType: true,
           }
         );
+
         cb(JWTType);
 
         pg2GqlMapper[compositeType.id] = {
@@ -136,6 +140,7 @@ export default (function PgJWTPlugin(
                   {}
                 )}`
             ),
+
             ", "
           )})`;
       });
@@ -145,4 +150,4 @@ export default (function PgJWTPlugin(
     [],
     ["PgIntrospection"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgMutationCreatePlugin.js b/packages/graphile-build-pg/src/plugins/PgMutationCreatePlugin.ts
similarity index 98%
rename from packages/graphile-build-pg/src/plugins/PgMutationCreatePlugin.js
rename to packages/graphile-build-pg/src/plugins/PgMutationCreatePlugin.ts
index e69f05513..f74970d78 100644
--- a/packages/graphile-build-pg/src/plugins/PgMutationCreatePlugin.js
+++ b/packages/graphile-build-pg/src/plugins/PgMutationCreatePlugin.ts
@@ -1,10 +1,9 @@
-// @flow
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 import debugFactory from "debug";
 
 const debug = debugFactory("graphile-build-pg");
 
-export default (function PgMutationCreatePlugin(
+export default function PgMutationCreatePlugin(
   builder,
   { pgDisableDefaultMutations }
 ) {
@@ -30,6 +29,7 @@ export default (function PgMutationCreatePlugin(
           GraphQLNonNull,
           GraphQLString,
         },
+
         pgColumnFilter,
         inflection,
         pgQueryFromResolveData: queryFromResolveData,
@@ -63,12 +63,14 @@ export default (function PgMutationCreatePlugin(
                 table.name
               }', so we're not generating a create mutation for it.`
             );
+
             return memo;
           }
           const TableInput = pgGetGqlInputTypeByTypeIdAndModifier(
             table.type.id,
             null
           );
+
           if (!TableInput) {
             debug(
               `There was no input type for table '${table.namespace.name}.${
@@ -88,6 +90,7 @@ export default (function PgMutationCreatePlugin(
                     "An arbitrary string value with no semantic meaning. Will be included in the payload verbatim. May be used to track mutations by the client.",
                   type: GraphQLString,
                 },
+
                 ...(TableInput
                   ? {
                       [inflection.tableFieldName(table)]: {
@@ -98,6 +101,7 @@ export default (function PgMutationCreatePlugin(
                   : null),
               },
             },
+
             {
               __origin: `Adding table create input type for ${describePgEntity(
                 table
@@ -112,6 +116,7 @@ export default (function PgMutationCreatePlugin(
               pgIntrospection: table,
             }
           );
+
           const PayloadType = newWithHooks(
             GraphQLObjectType,
             {
@@ -125,6 +130,7 @@ export default (function PgMutationCreatePlugin(
                       "The exact same `clientMutationId` that was provided in the mutation input, unchanged and unused. May be used by a client to track mutations.",
                     type: GraphQLString,
                   },
+
                   [tableName]: pgField(
                     build,
                     fieldWithHooks,
@@ -133,6 +139,7 @@ export default (function PgMutationCreatePlugin(
                       description: `The \`${tableTypeName}\` that was created by this mutation.`,
                       type: Table,
                     },
+
                     {
                       isPgCreatePayloadResultField: true,
                       pgFieldIntrospection: table,
@@ -141,6 +148,7 @@ export default (function PgMutationCreatePlugin(
                 };
               },
             },
+
             {
               __origin: `Adding table create payload type for ${describePgEntity(
                 table
@@ -158,6 +166,7 @@ export default (function PgMutationCreatePlugin(
               pgIntrospection: table,
             }
           );
+
           const fieldName = inflection.createField(table);
           memo = build.extend(
             memo,
@@ -171,6 +180,7 @@ export default (function PgMutationCreatePlugin(
                       pgColumnFilter(attr, build, context) &&
                       !omit(attr, "create")
                   );
+
                   return {
                     description: `Creates a single \`${tableTypeName}\`.`,
                     type: PayloadType,
@@ -179,17 +189,20 @@ export default (function PgMutationCreatePlugin(
                         type: new GraphQLNonNull(InputType),
                       },
                     },
+
                     async resolve(data, args, resolveContext, resolveInfo) {
                       const { input } = args;
                       const { pgClient } = resolveContext;
                       const parsedResolveInfoFragment = parseResolveInfo(
                         resolveInfo
                       );
+
                       parsedResolveInfoFragment.args = args; // Allow overriding via makeWrapResolversPlugin
                       const resolveData = getDataFromParsedResolveInfoFragment(
                         parsedResolveInfoFragment,
                         PayloadType
                       );
+
                       const insertedRowAlias = sql.identifier(Symbol());
                       const query = queryFromResolveData(
                         insertedRowAlias,
@@ -200,6 +213,7 @@ export default (function PgMutationCreatePlugin(
                         resolveContext,
                         resolveInfo.rootValue
                       );
+
                       const sqlColumns = [];
                       const sqlValues = [];
                       const inputData = input[inflection.tableFieldName(table)];
@@ -239,6 +253,7 @@ insert into ${sql.identifier(table.namespace.name, table.name)} ${
                           insertedRowAlias,
                           query
                         );
+
                         row = rows[0];
                         await pgClient.query(
                           "RELEASE SAVEPOINT graphql_mutation"
@@ -247,6 +262,7 @@ insert into ${sql.identifier(table.namespace.name, table.name)} ${
                         await pgClient.query(
                           "ROLLBACK TO SAVEPOINT graphql_mutation"
                         );
+
                         throw e;
                       }
                       return {
@@ -262,6 +278,7 @@ insert into ${sql.identifier(table.namespace.name, table.name)} ${
                 }
               ),
             },
+
             `Adding create mutation for ${describePgEntity(
               table
             )}. You can omit this default mutation with:\n\n  ${sqlCommentByAddingTags(
@@ -271,6 +288,7 @@ insert into ${sql.identifier(table.namespace.name, table.name)} ${
               }
             )}`
           );
+
           return memo;
         }, {}),
         `Adding default 'create' mutation to root mutation`
@@ -280,4 +298,4 @@ insert into ${sql.identifier(table.namespace.name, table.name)} ${
     [],
     ["PgTables"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgMutationPayloadEdgePlugin.js b/packages/graphile-build-pg/src/plugins/PgMutationPayloadEdgePlugin.ts
similarity index 98%
rename from packages/graphile-build-pg/src/plugins/PgMutationPayloadEdgePlugin.js
rename to packages/graphile-build-pg/src/plugins/PgMutationPayloadEdgePlugin.ts
index 670fba45f..068eeeed1 100644
--- a/packages/graphile-build-pg/src/plugins/PgMutationPayloadEdgePlugin.js
+++ b/packages/graphile-build-pg/src/plugins/PgMutationPayloadEdgePlugin.ts
@@ -1,8 +1,7 @@
-// @flow
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 import isString from "lodash/isString";
 
-export default (function PgMutationPayloadEdgePlugin(
+export default function PgMutationPayloadEdgePlugin(
   builder,
   { pgSimpleCollections, disableIssue397Fix }
 ) {
@@ -57,6 +56,7 @@ export default (function PgMutationPayloadEdgePlugin(
       const TableOrderByType = getTypeByName(
         inflection.orderByType(tableTypeName)
       );
+
       const TableEdgeType = getTypeByName(inflection.edge(tableTypeName));
       if (!TableEdgeType) {
         return fields;
@@ -89,6 +89,7 @@ export default (function PgMutationPayloadEdgePlugin(
                       type: new GraphQLList(
                         new GraphQLNonNull(TableOrderByType)
                       ),
+
                       defaultValue: defaultValueEnum
                         ? [defaultValueEnum.value]
                         : null,
@@ -133,10 +134,12 @@ export default (function PgMutationPayloadEdgePlugin(
                 };
               },
             },
+
             {
               isPgMutationPayloadEdgeField: true,
               pgFieldIntrospection: table,
             },
+
             false,
             {
               withQueryBuilder(queryBuilder, { parsedResolveInfoFragment }) {
@@ -195,6 +198,7 @@ export default (function PgMutationPayloadEdgePlugin(
             }
           ),
         },
+
         `Adding edge field for table ${describePgEntity(
           table
         )} to mutation payload '${Self.name}'`
@@ -202,4 +206,4 @@ export default (function PgMutationPayloadEdgePlugin(
     },
     ["PgMutationPayloadEdge"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgMutationProceduresPlugin.js b/packages/graphile-build-pg/src/plugins/PgMutationProceduresPlugin.ts
similarity index 92%
rename from packages/graphile-build-pg/src/plugins/PgMutationProceduresPlugin.js
rename to packages/graphile-build-pg/src/plugins/PgMutationProceduresPlugin.ts
index ce97f062a..d567e1d0b 100644
--- a/packages/graphile-build-pg/src/plugins/PgMutationProceduresPlugin.js
+++ b/packages/graphile-build-pg/src/plugins/PgMutationProceduresPlugin.ts
@@ -1,7 +1,6 @@
-// @flow
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 
-export default (function PgMutationProceduresPlugin(builder) {
+export default function PgMutationProceduresPlugin(builder) {
   builder.hook(
     "GraphQLObjectType:fields",
     (fields, build, context) => {
@@ -42,6 +41,7 @@ export default (function PgMutationProceduresPlugin(builder) {
                   isMutation: true,
                 }),
               },
+
               `Adding mutation field for ${describePgEntity(
                 proc
               )}. You can rename this field with:\n\n  ${sqlCommentByAddingTags(
@@ -61,4 +61,4 @@ export default (function PgMutationProceduresPlugin(builder) {
     },
     ["PgMutationProcedures"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgMutationUpdateDeletePlugin.js b/packages/graphile-build-pg/src/plugins/PgMutationUpdateDeletePlugin.ts
similarity index 99%
rename from packages/graphile-build-pg/src/plugins/PgMutationUpdateDeletePlugin.js
rename to packages/graphile-build-pg/src/plugins/PgMutationUpdateDeletePlugin.ts
index d163aa12c..6bb93373b 100644
--- a/packages/graphile-build-pg/src/plugins/PgMutationUpdateDeletePlugin.js
+++ b/packages/graphile-build-pg/src/plugins/PgMutationUpdateDeletePlugin.ts
@@ -1,10 +1,9 @@
-// @flow
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 import debugFactory from "debug";
 
 const debug = debugFactory("graphile-build-pg");
 
-export default (async function PgMutationUpdateDeletePlugin(
+export default async function PgMutationUpdateDeletePlugin(
   builder,
   { pgDisableDefaultMutations }
 ) {
@@ -36,6 +35,7 @@ export default (async function PgMutationUpdateDeletePlugin(
           GraphQLObjectType,
           GraphQLID,
         },
+
         pgColumnFilter,
         inflection,
         pgQueryFromResolveData: queryFromResolveData,
@@ -75,6 +75,7 @@ export default (async function PgMutationUpdateDeletePlugin(
                 table.type.id,
                 null
               );
+
               if (!TableType) {
                 return memo;
               }
@@ -109,6 +110,7 @@ export default (async function PgMutationUpdateDeletePlugin(
                     input[
                       inflection.patchField(inflection.tableFieldName(table))
                     ];
+
                   table.attributes.forEach(attr => {
                     // PERFORMANCE: These used to be .filter(...) calls
                     if (!pgColumnFilter(attr, build, context)) return;
@@ -131,6 +133,7 @@ update ${sql.identifier(table.namespace.name, table.name)} set ${sql.join(
                     sqlColumns.map(
                       (col, i) => sql.fragment`${col} = ${sqlValues[i]}`
                     ),
+
                     ", "
                   )}
 where ${condition}
@@ -152,6 +155,7 @@ returning *`;
                   resolveContext,
                   resolveInfo.rootValue
                 );
+
                 let row;
                 try {
                   await pgClient.query("SAVEPOINT graphql_mutation");
@@ -162,12 +166,14 @@ returning *`;
                     modifiedRowAlias,
                     query
                   );
+
                   row = rows[0];
                   await pgClient.query("RELEASE SAVEPOINT graphql_mutation");
                 } catch (e) {
                   await pgClient.query(
                     "ROLLBACK TO SAVEPOINT graphql_mutation"
                   );
+
                   throw e;
                 }
                 if (!row) {
@@ -186,14 +192,17 @@ returning *`;
                 const uniqueConstraints = table.constraints.filter(
                   con => con.type === "u" || con.type === "p"
                 );
+
                 const Table = pgGetGqlTypeByTypeIdAndModifier(
                   table.type.id,
                   null
                 );
+
                 const tableTypeName = Table.name;
                 const TablePatch = getTypeByName(
                   inflection.patchType(Table.name)
                 );
+
                 const PayloadType = newWithHooks(
                   GraphQLObjectType,
                   {
@@ -209,6 +218,7 @@ returning *`;
                       const deletedNodeIdFieldName = inflection.deletedNodeId(
                         table
                       );
+
                       return Object.assign(
                         {
                           clientMutationId: {
@@ -216,6 +226,7 @@ returning *`;
                               "The exact same `clientMutationId` that was provided in the mutation input, unchanged and unused. May be used by a client to track mutations.",
                             type: GraphQLString,
                           },
+
                           [tableName]: pgField(
                             build,
                             fieldWithHooks,
@@ -224,10 +235,12 @@ returning *`;
                               description: `The \`${tableTypeName}\` that was ${mode}d by this mutation.`,
                               type: Table,
                             },
+
                             {},
                             false
                           ),
                         },
+
                         mode === "delete"
                           ? {
                               [deletedNodeIdFieldName]: fieldWithHooks(
@@ -242,6 +255,7 @@ returning *`;
                                     fieldDataGeneratorsByTableType[
                                       nodeIdFieldName
                                     ];
+
                                   if (gens) {
                                     gens.forEach(gen => addDataGenerator(gen));
                                   }
@@ -267,6 +281,7 @@ returning *`;
                       );
                     },
                   },
+
                   {
                     __origin: `Adding table ${mode} mutation payload type for ${describePgEntity(
                       table
@@ -307,11 +322,13 @@ returning *`;
                               "An arbitrary string value with no semantic meaning. Will be included in the payload verbatim. May be used to track mutations by the client.",
                             type: GraphQLString,
                           },
+
                           [nodeIdFieldName]: {
                             description: `The globally unique \`ID\` which will identify a single \`${tableTypeName}\` to be ${mode}d.`,
                             type: new GraphQLNonNull(GraphQLID),
                           },
                         },
+
                         mode === "update"
                           ? {
                               [inflection.patchField(
@@ -324,6 +341,7 @@ returning *`;
                           : null
                       ),
                     },
+
                     {
                       __origin: `Adding table ${mode} (by node ID) mutation input type for ${describePgEntity(
                         table
@@ -363,6 +381,7 @@ returning *`;
                                 type: new GraphQLNonNull(InputType),
                               },
                             },
+
                             async resolve(
                               parent,
                               args,
@@ -401,6 +420,7 @@ returning *`;
                                           key.typeModifier
                                         )}`
                                     ),
+
                                     ") and ("
                                   )})`,
                                   context,
@@ -422,6 +442,7 @@ returning *`;
                         }
                       ),
                     },
+
                     "Adding ${mode} mutation for ${describePgEntity(table)}"
                   );
                 }
@@ -460,6 +481,7 @@ returning *`;
                             type: GraphQLString,
                           },
                         },
+
                         mode === "update"
                           ? {
                               [inflection.patchField(
@@ -480,10 +502,12 @@ returning *`;
                               )
                             ),
                           };
+
                           return memo;
                         }, {})
                       ),
                     },
+
                     {
                       __origin: `Adding table ${mode} mutation input type for ${describePgEntity(
                         constraint
@@ -524,6 +548,7 @@ returning *`;
                                 type: new GraphQLNonNull(InputType),
                               },
                             },
+
                             async resolve(
                               parent,
                               args,
@@ -549,6 +574,7 @@ returning *`;
                                         key.typeModifier
                                       )}`
                                   ),
+
                                   ") and ("
                                 )})`,
                                 context,
@@ -567,6 +593,7 @@ returning *`;
                         }
                       ),
                     },
+
                     `Adding ${mode} mutation for ${describePgEntity(
                       constraint
                     )}`
@@ -577,9 +604,10 @@ returning *`;
             }, outerMemo),
           {}
         ),
+
         `Adding default update/delete mutations to root Mutation type`
       );
     },
     ["PgMutationUpdateDelete"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgNodeAliasPostGraphile.js b/packages/graphile-build-pg/src/plugins/PgNodeAliasPostGraphile.ts
similarity index 80%
rename from packages/graphile-build-pg/src/plugins/PgNodeAliasPostGraphile.js
rename to packages/graphile-build-pg/src/plugins/PgNodeAliasPostGraphile.ts
index adaacc140..e04aa8f8c 100644
--- a/packages/graphile-build-pg/src/plugins/PgNodeAliasPostGraphile.js
+++ b/packages/graphile-build-pg/src/plugins/PgNodeAliasPostGraphile.ts
@@ -1,7 +1,6 @@
-// @flow
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 
-export default (async function PgNodeAliasPostGraphile(builder) {
+export default async function PgNodeAliasPostGraphile(builder) {
   builder.hook(
     "GraphQLObjectType",
     (object, build, context) => {
@@ -23,4 +22,4 @@ export default (async function PgNodeAliasPostGraphile(builder) {
     },
     ["PgNodeAliasPostGraphile"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgOrderAllColumnsPlugin.js b/packages/graphile-build-pg/src/plugins/PgOrderAllColumnsPlugin.ts
similarity index 94%
rename from packages/graphile-build-pg/src/plugins/PgOrderAllColumnsPlugin.js
rename to packages/graphile-build-pg/src/plugins/PgOrderAllColumnsPlugin.ts
index fd8c12bd8..38dab7d28 100644
--- a/packages/graphile-build-pg/src/plugins/PgOrderAllColumnsPlugin.js
+++ b/packages/graphile-build-pg/src/plugins/PgOrderAllColumnsPlugin.ts
@@ -1,7 +1,6 @@
-// @flow
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 
-export default (function PgOrderAllColumnsPlugin(builder) {
+export default function PgOrderAllColumnsPlugin(builder) {
   builder.hook(
     "GraphQLEnumType:values",
     (values, build, context) => {
@@ -40,6 +39,7 @@ export default (function PgOrderAllColumnsPlugin(builder) {
                 },
               },
             },
+
             `Adding ascending orderBy enum value for ${describePgEntity(
               attr
             )}. You can rename this field with:\n\n  ${sqlCommentByAddingTags(
@@ -49,6 +49,7 @@ export default (function PgOrderAllColumnsPlugin(builder) {
               }
             )}`
           );
+
           memo = extend(
             memo,
             {
@@ -60,6 +61,7 @@ export default (function PgOrderAllColumnsPlugin(builder) {
                 },
               },
             },
+
             `Adding descending orderBy enum value for ${describePgEntity(
               attr
             )}. You can rename this field with:\n\n  ${sqlCommentByAddingTags(
@@ -69,6 +71,7 @@ export default (function PgOrderAllColumnsPlugin(builder) {
               }
             )}`
           );
+
           return memo;
         }, {}),
         `Adding order values from table '${table.name}'`
@@ -76,4 +79,4 @@ export default (function PgOrderAllColumnsPlugin(builder) {
     },
     ["PgOrderAllColumns"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgOrderByPrimaryKeyPlugin.js b/packages/graphile-build-pg/src/plugins/PgOrderByPrimaryKeyPlugin.ts
similarity index 89%
rename from packages/graphile-build-pg/src/plugins/PgOrderByPrimaryKeyPlugin.js
rename to packages/graphile-build-pg/src/plugins/PgOrderByPrimaryKeyPlugin.ts
index dc905fa00..8954694cf 100644
--- a/packages/graphile-build-pg/src/plugins/PgOrderByPrimaryKeyPlugin.js
+++ b/packages/graphile-build-pg/src/plugins/PgOrderByPrimaryKeyPlugin.ts
@@ -1,7 +1,6 @@
-// @flow
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 
-export default (function PgOrderByPrimaryKeyPlugin(builder) {
+export default function PgOrderByPrimaryKeyPlugin(builder) {
   builder.hook(
     "GraphQLEnumType:values",
     (values, build, context) => {
@@ -29,6 +28,7 @@ export default (function PgOrderByPrimaryKeyPlugin(builder) {
               unique: true,
             },
           },
+
           PRIMARY_KEY_DESC: {
             value: {
               alias: "primary_key_desc",
@@ -37,9 +37,10 @@ export default (function PgOrderByPrimaryKeyPlugin(builder) {
             },
           },
         },
+
         `Adding primary key asc/desc sort to table '${table.name}'`
       );
     },
     ["PgOrderByPrimaryKey"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgOrderComputedColumnsPlugin.js b/packages/graphile-build-pg/src/plugins/PgOrderComputedColumnsPlugin.ts
similarity index 96%
rename from packages/graphile-build-pg/src/plugins/PgOrderComputedColumnsPlugin.js
rename to packages/graphile-build-pg/src/plugins/PgOrderComputedColumnsPlugin.ts
index 7ba59ea0f..be1b80c92 100644
--- a/packages/graphile-build-pg/src/plugins/PgOrderComputedColumnsPlugin.js
+++ b/packages/graphile-build-pg/src/plugins/PgOrderComputedColumnsPlugin.ts
@@ -1,8 +1,7 @@
-// @flow
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 import { getComputedColumnDetails } from "./PgComputedColumnsPlugin";
 
-export default (function PgOrderComputedColumnsPlugin(builder) {
+export default function PgOrderComputedColumnsPlugin(builder) {
   builder.hook(
     "GraphQLEnumType:values",
     (values, build, context) => {
@@ -36,6 +35,7 @@ export default (function PgOrderComputedColumnsPlugin(builder) {
             table,
             proc
           );
+
           if (!computedColumnDetails) return memo;
           const { pseudoColumnName } = computedColumnDetails;
 
@@ -65,6 +65,7 @@ export default (function PgOrderComputedColumnsPlugin(builder) {
         },
         []
       );
+
       return extend(
         values,
         compatibleComputedColumns.reduce((memo, { proc, pseudoColumnName }) => {
@@ -74,6 +75,7 @@ export default (function PgOrderComputedColumnsPlugin(builder) {
             table,
             true
           );
+
           const descFieldName = inflection.orderByComputedColumnEnum(
             pseudoColumnName,
             proc,
@@ -100,10 +102,12 @@ export default (function PgOrderComputedColumnsPlugin(builder) {
                 },
               },
             },
+
             `Adding ascending orderBy enum value for ${describePgEntity(
               proc
             )}. You can rename this field by removing the '@sortable' smart comment from the function.`
           );
+
           memo = extend(
             memo,
             {
@@ -115,10 +119,12 @@ export default (function PgOrderComputedColumnsPlugin(builder) {
                 },
               },
             },
+
             `Adding descending orderBy enum value for ${describePgEntity(
               proc
             )}. You can rename this field by removing the '@sortable' smart comment from the function.`
           );
+
           return memo;
         }, {}),
         `Adding order values from table '${table.name}'`
@@ -126,4 +132,4 @@ export default (function PgOrderComputedColumnsPlugin(builder) {
     },
     ["PgOrderComputedColumns"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgQueryProceduresPlugin.js b/packages/graphile-build-pg/src/plugins/PgQueryProceduresPlugin.ts
similarity index 96%
rename from packages/graphile-build-pg/src/plugins/PgQueryProceduresPlugin.js
rename to packages/graphile-build-pg/src/plugins/PgQueryProceduresPlugin.ts
index 907bd39ab..8a6ca12af 100644
--- a/packages/graphile-build-pg/src/plugins/PgQueryProceduresPlugin.js
+++ b/packages/graphile-build-pg/src/plugins/PgQueryProceduresPlugin.ts
@@ -1,7 +1,6 @@
-// @flow
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 
-export default (function PgQueryProceduresPlugin(
+export default function PgQueryProceduresPlugin(
   builder,
   { pgSimpleCollections }
 ) {
@@ -78,6 +77,7 @@ export default (function PgQueryProceduresPlugin(
                     forceList,
                   }),
                 },
+
                 `Adding query field for ${describePgEntity(
                   proc
                 )}. You can rename this field with:\n\n  ${sqlCommentByAddingTags(
@@ -109,4 +109,4 @@ export default (function PgQueryProceduresPlugin(
     },
     ["PgQueryProcedures"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgRecordFunctionConnectionPlugin.js b/packages/graphile-build-pg/src/plugins/PgRecordFunctionConnectionPlugin.ts
similarity index 98%
rename from packages/graphile-build-pg/src/plugins/PgRecordFunctionConnectionPlugin.js
rename to packages/graphile-build-pg/src/plugins/PgRecordFunctionConnectionPlugin.ts
index 684c8093a..0a2a4fcab 100644
--- a/packages/graphile-build-pg/src/plugins/PgRecordFunctionConnectionPlugin.js
+++ b/packages/graphile-build-pg/src/plugins/PgRecordFunctionConnectionPlugin.ts
@@ -1,9 +1,8 @@
-// @flow
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 
 const base64 = str => Buffer.from(String(str)).toString("base64");
 
-export default (function PgRecordFunctionConnectionPlugin(
+export default function PgRecordFunctionConnectionPlugin(
   builder,
   { pgForbidSetofFunctionsToReturnNull = false }
 ) {
@@ -44,6 +43,7 @@ export default (function PgRecordFunctionConnectionPlugin(
         const NodeType = getTypeByName(
           inflection.recordFunctionReturnType(proc)
         );
+
         if (!NodeType) {
           throw new Error(
             `Do not have a node type '${inflection.recordFunctionReturnType(
@@ -64,6 +64,7 @@ export default (function PgRecordFunctionConnectionPlugin(
                     addDataGenerator(() => ({
                       usesCursor: [true],
                     }));
+
                     return {
                       description: "A cursor for use in pagination.",
                       type: Cursor,
@@ -76,6 +77,7 @@ export default (function PgRecordFunctionConnectionPlugin(
                     isCursorField: true,
                   }
                 ),
+
                 node: pgField(
                   build,
                   fieldWithHooks,
@@ -88,19 +90,23 @@ export default (function PgRecordFunctionConnectionPlugin(
                       !pgForbidSetofFunctionsToReturnNull,
                       NodeType
                     ),
+
                     resolve(data, _args, _context, resolveInfo) {
                       const safeAlias = getSafeAliasFromResolveInfo(
                         resolveInfo
                       );
+
                       return data[safeAlias];
                     },
                   },
+
                   {},
                   false
                 ),
               };
             },
           },
+
           {
             __origin: `Adding function result edge type for ${describePgEntity(
               proc
@@ -133,11 +139,13 @@ export default (function PgRecordFunctionConnectionPlugin(
                       nullableIf(!pgForbidSetofFunctionsToReturnNull, NodeType)
                     )
                   ),
+
                   resolve(data, _args, _context, resolveInfo) {
                     const safeAlias = getSafeAliasFromResolveInfo(resolveInfo);
                     return data.data.map(entry => entry[safeAlias]);
                   },
                 }),
+
                 edges: pgField(
                   build,
                   fieldWithHooks,
@@ -149,16 +157,19 @@ export default (function PgRecordFunctionConnectionPlugin(
                     type: new GraphQLNonNull(
                       new GraphQLList(new GraphQLNonNull(EdgeType))
                     ),
+
                     resolve(data, _args, _context, resolveInfo) {
                       const safeAlias = getSafeAliasFromResolveInfo(
                         resolveInfo
                       );
+
                       return data.data.map(entry => ({
                         __cursor: entry.__cursor,
                         ...entry[safeAlias],
                       }));
                     },
                   },
+
                   {},
                   false,
                   {
@@ -168,6 +179,7 @@ export default (function PgRecordFunctionConnectionPlugin(
               };
             },
           },
+
           {
             __origin: `Adding function connection type for ${describePgEntity(
               proc
@@ -188,4 +200,4 @@ export default (function PgRecordFunctionConnectionPlugin(
     },
     ["PgRecordFunctionConnection"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgRecordReturnTypesPlugin.js b/packages/graphile-build-pg/src/plugins/PgRecordReturnTypesPlugin.ts
similarity index 97%
rename from packages/graphile-build-pg/src/plugins/PgRecordReturnTypesPlugin.js
rename to packages/graphile-build-pg/src/plugins/PgRecordReturnTypesPlugin.ts
index 44f4bb0c1..d1f437bc4 100644
--- a/packages/graphile-build-pg/src/plugins/PgRecordReturnTypesPlugin.js
+++ b/packages/graphile-build-pg/src/plugins/PgRecordReturnTypesPlugin.ts
@@ -1,7 +1,6 @@
-// @flow
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 
-export default (function PgRecordReturnTypesPlugin(builder) {
+export default function PgRecordReturnTypesPlugin(builder) {
   builder.hook(
     "init",
     (_, build) => {
@@ -43,8 +42,9 @@ export default (function PgRecordReturnTypesPlugin(builder) {
         const argModesWithOutput = [
           "o", // OUT,
           "b", // INOUT
-          "t", // TABLE
+          "t",
         ];
+
         const outputArgNames = proc.argTypeIds.reduce((prev, _, idx) => {
           if (argModesWithOutput.includes(proc.argModes[idx])) {
             prev.push(proc.argNames[idx] || "");
@@ -87,10 +87,12 @@ export default (function PgRecordReturnTypesPlugin(builder) {
                   outputArgName,
                   idx + 1
                 );
+
                 const fieldType = pgGetGqlTypeByTypeIdAndModifier(
                   outputArgTypes[idx].id,
                   null
                 );
+
                 if (memo[fieldName]) {
                   throw new Error(
                     `Tried to register field name '${fieldName}' twice in '${describePgEntity(
@@ -106,6 +108,7 @@ export default (function PgRecordReturnTypesPlugin(builder) {
                       const safeAlias = getSafeAliasFromAlias(
                         parsedResolveInfoFragment.alias
                       );
+
                       return {
                         pgQuery: queryBuilder => {
                           queryBuilder.select(
@@ -124,6 +127,7 @@ export default (function PgRecordReturnTypesPlugin(builder) {
                               outputArgTypes[idx],
                               null
                             ),
+
                             safeAlias
                           );
                         },
@@ -135,16 +139,19 @@ export default (function PgRecordReturnTypesPlugin(builder) {
                         const safeAlias = getSafeAliasFromResolveInfo(
                           resolveInfo
                         );
+
                         return data[safeAlias];
                       },
                     };
                   },
                   {}
                 );
+
                 return memo;
               }, {});
             },
           },
+
           {
             __origin: `Adding record return type for ${describePgEntity(
               proc
@@ -168,4 +175,4 @@ export default (function PgRecordReturnTypesPlugin(builder) {
     },
     ["PgRecordReturnTypes"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgRowByUniqueConstraint.js b/packages/graphile-build-pg/src/plugins/PgRowByUniqueConstraint.ts
similarity index 98%
rename from packages/graphile-build-pg/src/plugins/PgRowByUniqueConstraint.js
rename to packages/graphile-build-pg/src/plugins/PgRowByUniqueConstraint.ts
index 2d265c24d..8c26e6340 100644
--- a/packages/graphile-build-pg/src/plugins/PgRowByUniqueConstraint.js
+++ b/packages/graphile-build-pg/src/plugins/PgRowByUniqueConstraint.ts
@@ -1,8 +1,7 @@
-// @flow
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 import debugSql from "./debugSql";
 
-export default (async function PgRowByUniqueConstraint(
+export default async function PgRowByUniqueConstraint(
   builder,
   { subscriptions }
 ) {
@@ -43,14 +42,17 @@ export default (async function PgRowByUniqueConstraint(
             table.type.id,
             null
           );
+
           const sqlFullTableName = sql.identifier(
             table.namespace.name,
             table.name
           );
+
           if (TableType) {
             const uniqueConstraints = table.constraints.filter(
               con => con.type === "u" || con.type === "p"
             );
+
             uniqueConstraints.forEach(constraint => {
               if (omit(constraint, "read")) {
                 return;
@@ -69,11 +71,13 @@ export default (async function PgRowByUniqueConstraint(
                 table,
                 constraint
               );
+
               const keysIncludingMeta = keys.map(key => ({
                 ...key,
                 sqlIdentifier: sql.identifier(key.name),
                 columnName: inflection.column(key),
               }));
+
               // Precomputation for performance
               const queryFromResolveDataOptions = {
                 useAsterisk: false, // Because it's only a single relation, no need
@@ -107,6 +111,7 @@ export default (async function PgRowByUniqueConstraint(
                           typeId,
                           typeModifier
                         );
+
                         if (!InputType) {
                           throw new Error(
                             `Could not find input type for key '${name}' on type '${
@@ -117,10 +122,12 @@ export default (async function PgRowByUniqueConstraint(
                         memo[columnName] = {
                           type: new GraphQLNonNull(InputType),
                         };
+
                         return memo;
                       },
                       {}
                     ),
+
                     async resolve(parent, args, resolveContext, resolveInfo) {
                       const { pgClient } = resolveContext;
                       const liveRecord =
@@ -129,11 +136,13 @@ export default (async function PgRowByUniqueConstraint(
                       const parsedResolveInfoFragment = parseResolveInfo(
                         resolveInfo
                       );
+
                       parsedResolveInfoFragment.args = args; // Allow overriding via makeWrapResolversPlugin
                       const resolveData = getDataFromParsedResolveInfoFragment(
                         parsedResolveInfoFragment,
                         TableType
                       );
+
                       const query = queryFromResolveData(
                         sqlFullTableName,
                         undefined,
@@ -144,6 +153,7 @@ export default (async function PgRowByUniqueConstraint(
                         resolveContext,
                         resolveInfo.rootValue
                       );
+
                       const { text, values } = sql.compile(query);
                       if (debugSql.enabled) debugSql(text);
                       const {
@@ -170,4 +180,4 @@ export default (async function PgRowByUniqueConstraint(
     },
     ["PgRowByUniqueConstraint"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgRowNode.js b/packages/graphile-build-pg/src/plugins/PgRowNode.ts
similarity index 98%
rename from packages/graphile-build-pg/src/plugins/PgRowNode.js
rename to packages/graphile-build-pg/src/plugins/PgRowNode.ts
index 4cee497e8..c9f5b3a16 100644
--- a/packages/graphile-build-pg/src/plugins/PgRowNode.js
+++ b/packages/graphile-build-pg/src/plugins/PgRowNode.ts
@@ -1,8 +1,7 @@
-// @flow
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 import debugSql from "./debugSql";
 
-export default (async function PgRowNode(builder, { subscriptions }) {
+export default async function PgRowNode(builder, { subscriptions }) {
   builder.hook(
     "GraphQLObjectType",
     (object, build, context) => {
@@ -78,6 +77,7 @@ export default (async function PgRowNode(builder, { subscriptions }) {
             resolveContext,
             resolveInfo && resolveInfo.rootValue
           );
+
           const { text, values } = sql.compile(query);
           if (debugSql.enabled) debugSql(text);
           const {
@@ -89,6 +89,7 @@ export default (async function PgRowNode(builder, { subscriptions }) {
           return row;
         }
       );
+
       return object;
     },
     ["PgRowNode"]
@@ -134,10 +135,12 @@ export default (async function PgRowNode(builder, { subscriptions }) {
             table.type.id,
             null
           );
+
           const sqlFullTableName = sql.identifier(
             table.namespace.name,
             table.name
           );
+
           if (TableType) {
             const primaryKeyConstraint = table.primaryKeyConstraint;
             if (!primaryKeyConstraint) {
@@ -165,6 +168,7 @@ export default (async function PgRowNode(builder, { subscriptions }) {
                           type: new GraphQLNonNull(GraphQLID),
                         },
                       },
+
                       async resolve(parent, args, resolveContext, resolveInfo) {
                         const { pgClient } = resolveContext;
                         const liveRecord =
@@ -186,11 +190,13 @@ export default (async function PgRowNode(builder, { subscriptions }) {
                           const parsedResolveInfoFragment = parseResolveInfo(
                             resolveInfo
                           );
+
                           parsedResolveInfoFragment.args = args; // Allow overriding via makeWrapResolversPlugin
                           const resolveData = getDataFromParsedResolveInfoFragment(
                             parsedResolveInfoFragment,
                             TableType
                           );
+
                           const query = queryFromResolveData(
                             sqlFullTableName,
                             undefined,
@@ -217,6 +223,7 @@ export default (async function PgRowNode(builder, { subscriptions }) {
                             resolveContext,
                             resolveInfo.rootValue
                           );
+
                           const { text, values } = sql.compile(query);
                           if (debugSql.enabled) debugSql(text);
                           const {
@@ -238,6 +245,7 @@ export default (async function PgRowNode(builder, { subscriptions }) {
                   }
                 ),
               },
+
               `Adding row by globally unique identifier field for ${describePgEntity(
                 table
               )}. You can rename this table via:\n\n  ${sqlCommentByAddingTags(
@@ -253,4 +261,4 @@ export default (async function PgRowNode(builder, { subscriptions }) {
     },
     ["PgRowNode"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgScalarFunctionConnectionPlugin.js b/packages/graphile-build-pg/src/plugins/PgScalarFunctionConnectionPlugin.ts
similarity index 97%
rename from packages/graphile-build-pg/src/plugins/PgScalarFunctionConnectionPlugin.js
rename to packages/graphile-build-pg/src/plugins/PgScalarFunctionConnectionPlugin.ts
index ad00ca704..d53b539e2 100644
--- a/packages/graphile-build-pg/src/plugins/PgScalarFunctionConnectionPlugin.js
+++ b/packages/graphile-build-pg/src/plugins/PgScalarFunctionConnectionPlugin.ts
@@ -1,9 +1,8 @@
-// @flow
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 
 const base64 = str => Buffer.from(String(str)).toString("base64");
 
-export default (function PgScalarFunctionConnectionPlugin(builder) {
+export default function PgScalarFunctionConnectionPlugin(builder) {
   builder.hook(
     "init",
     (_, build) => {
@@ -18,6 +17,7 @@ export default (function PgScalarFunctionConnectionPlugin(builder) {
           GraphQLList,
           GraphQLString,
         },
+
         inflection,
         pgOmit: omit,
         describePgEntity,
@@ -62,6 +62,7 @@ export default (function PgScalarFunctionConnectionPlugin(builder) {
                     addDataGenerator(() => ({
                       usesCursor: [true],
                     }));
+
                     return {
                       description: "A cursor for use in pagination.",
                       type: Cursor,
@@ -74,6 +75,7 @@ export default (function PgScalarFunctionConnectionPlugin(builder) {
                     isCursorField: true,
                   }
                 ),
+
                 node: {
                   description: `The \`${
                     NodeType.name
@@ -86,6 +88,7 @@ export default (function PgScalarFunctionConnectionPlugin(builder) {
               };
             },
           },
+
           {
             __origin: `Adding function result edge type for ${describePgEntity(
               proc
@@ -118,6 +121,7 @@ export default (function PgScalarFunctionConnectionPlugin(builder) {
                     return data.data.map(entry => entry.value);
                   },
                 }),
+
                 edges: pgField(
                   build,
                   fieldWithHooks,
@@ -129,10 +133,12 @@ export default (function PgScalarFunctionConnectionPlugin(builder) {
                     type: new GraphQLNonNull(
                       new GraphQLList(new GraphQLNonNull(EdgeType))
                     ),
+
                     resolve(data) {
                       return data.data;
                     },
                   },
+
                   {},
                   false,
                   {
@@ -142,6 +148,7 @@ export default (function PgScalarFunctionConnectionPlugin(builder) {
               };
             },
           },
+
           {
             __origin: `Adding function connection type for ${describePgEntity(
               proc
@@ -164,4 +171,4 @@ export default (function PgScalarFunctionConnectionPlugin(builder) {
     [],
     ["PgTypes"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgTablesPlugin.js b/packages/graphile-build-pg/src/plugins/PgTablesPlugin.ts
similarity index 99%
rename from packages/graphile-build-pg/src/plugins/PgTablesPlugin.js
rename to packages/graphile-build-pg/src/plugins/PgTablesPlugin.ts
index 891346110..29315f716 100644
--- a/packages/graphile-build-pg/src/plugins/PgTablesPlugin.js
+++ b/packages/graphile-build-pg/src/plugins/PgTablesPlugin.ts
@@ -1,5 +1,4 @@
-// @flow
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 const base64 = str => Buffer.from(String(str)).toString("base64");
 
 const hasNonNullKey = row => {
@@ -19,7 +18,7 @@ const hasNonNullKey = row => {
   return false;
 };
 
-export default (function PgTablesPlugin(
+export default function PgTablesPlugin(
   builder,
   { pgForbidSetofFunctionsToReturnNull = false, subscriptions = false }
 ) {
@@ -57,6 +56,7 @@ export default (function PgTablesPlugin(
           GraphQLList,
           GraphQLInputObjectType,
         },
+
         inflection,
         describePgEntity,
         sqlCommentByAddingTags,
@@ -164,6 +164,7 @@ export default (function PgTablesPlugin(
                             return identifier;
                           }
                         );
+
                         return getNodeIdForTypeAndIdentifiers(
                           Self,
                           ...finalIdentifiers
@@ -174,6 +175,7 @@ export default (function PgTablesPlugin(
                   return fields;
                 },
               },
+
               {
                 __origin: `Adding table type for ${describePgEntity(
                   table
@@ -189,6 +191,7 @@ export default (function PgTablesPlugin(
                 isPgCompositeType: !table.isSelectable,
               }
             );
+
             cb(TableType);
             const pgCreateInputFields = {};
             const pgPatchInputFields = {};
@@ -199,6 +202,7 @@ export default (function PgTablesPlugin(
                 description: `An input for mutations affecting \`${tableTypeName}\``,
                 name: inflection.inputType(TableType),
               },
+
               {
                 __origin: `Adding table input type for ${describePgEntity(
                   table
@@ -218,9 +222,11 @@ export default (function PgTablesPlugin(
                     type: pgType,
                     typeModifier,
                   };
+
                   return spec;
                 },
               },
+
               true // If no fields, skip type automatically
             );
 
@@ -236,6 +242,7 @@ export default (function PgTablesPlugin(
                   description: `Represents an update to a \`${tableTypeName}\`. Fields that are set will be updated.`,
                   name: inflection.patchType(TableType),
                 },
+
                 {
                   __origin: `Adding table patch type for ${describePgEntity(
                     table
@@ -261,9 +268,11 @@ export default (function PgTablesPlugin(
                       type: pgType,
                       typeModifier,
                     };
+
                     return spec;
                   },
                 },
+
                 true // Safe to skip this if no fields support updating
               );
               TableBaseInputType = newWithHooks(
@@ -272,6 +281,7 @@ export default (function PgTablesPlugin(
                   description: `An input representation of \`${tableTypeName}\` with nullable fields.`,
                   name: inflection.baseInputType(TableType),
                 },
+
                 {
                   __origin: `Adding table base input type for ${describePgEntity(
                     table
@@ -297,6 +307,7 @@ export default (function PgTablesPlugin(
                       type: pgType,
                       typeModifier,
                     };
+
                     return spec;
                   },
                 }
@@ -360,6 +371,7 @@ export default (function PgTablesPlugin(
                             }
                           },
                         }));
+
                         return {
                           description: "A cursor for use in pagination.",
                           type: Cursor,
@@ -375,6 +387,7 @@ export default (function PgTablesPlugin(
                         isCursorField: true,
                       }
                     ),
+
                     node: pgField(
                       build,
                       fieldWithHooks,
@@ -385,14 +398,17 @@ export default (function PgTablesPlugin(
                           !pgForbidSetofFunctionsToReturnNull,
                           TableType
                         ),
+
                         resolve(data, _args, resolveContext, resolveInfo) {
                           const safeAlias = getSafeAliasFromResolveInfo(
                             resolveInfo
                           );
+
                           const record = handleNullRow(
                             data[safeAlias],
                             data.__identifiers
                           );
+
                           const liveRecord =
                             resolveInfo.rootValue &&
                             resolveInfo.rootValue.liveRecord;
@@ -407,6 +423,7 @@ export default (function PgTablesPlugin(
                           return record;
                         },
                       },
+
                       {},
                       false,
                       {
@@ -420,6 +437,7 @@ export default (function PgTablesPlugin(
                   };
                 },
               },
+
               {
                 __origin: `Adding table edge type for ${describePgEntity(
                   table
@@ -435,6 +453,7 @@ export default (function PgTablesPlugin(
                 pgIntrospection: table,
               }
             );
+
             const PageInfo = getTypeByName(inflection.builtin("PageInfo"));
 
             /*const ConnectionType = */
@@ -460,10 +479,12 @@ export default (function PgTablesPlugin(
                             )
                           )
                         ),
+
                         resolve(data, _args, resolveContext, resolveInfo) {
                           const safeAlias = getSafeAliasFromResolveInfo(
                             resolveInfo
                           );
+
                           const liveRecord =
                             resolveInfo.rootValue &&
                             resolveInfo.rootValue.liveRecord;
@@ -472,6 +493,7 @@ export default (function PgTablesPlugin(
                               entry[safeAlias],
                               entry[safeAlias].__identifiers
                             );
+
                             if (
                               record &&
                               liveRecord &&
@@ -489,6 +511,7 @@ export default (function PgTablesPlugin(
                           });
                         },
                       },
+
                       {},
                       false,
                       {
@@ -499,6 +522,7 @@ export default (function PgTablesPlugin(
                         },
                       }
                     ),
+
                     edges: pgField(
                       build,
                       fieldWithHooks,
@@ -508,22 +532,26 @@ export default (function PgTablesPlugin(
                         type: new GraphQLNonNull(
                           new GraphQLList(new GraphQLNonNull(EdgeType))
                         ),
+
                         resolve(data, _args, _context, resolveInfo) {
                           const safeAlias = getSafeAliasFromResolveInfo(
                             resolveInfo
                           );
+
                           return data.data.map(entry => ({
                             ...entry,
                             ...entry[safeAlias],
                           }));
                         },
                       },
+
                       {},
                       false,
                       {
                         hoistCursor: true,
                       }
                     ),
+
                     pageInfo: PageInfo && {
                       description: "Information to aid in pagination.",
                       type: new GraphQLNonNull(PageInfo),
@@ -534,6 +562,7 @@ export default (function PgTablesPlugin(
                   };
                 },
               },
+
               {
                 __origin: `Adding table connection type for ${describePgEntity(
                   table
@@ -553,6 +582,7 @@ export default (function PgTablesPlugin(
           },
           true
         );
+
         pgRegisterGqlInputTypeByTypeId(
           tablePgType.id,
           (_set, modifier) => {
@@ -561,6 +591,7 @@ export default (function PgTablesPlugin(
               tablePgType.id,
               null
             );
+
             // This must come after the pgGetGqlTypeByTypeIdAndModifier call
             if (modifier === "patch") {
               // TODO: v5: move the definition from above down here
@@ -593,10 +624,12 @@ export default (function PgTablesPlugin(
                 tablePgType.id,
                 null
               );
+
               return new GraphQLList(TableType);
             },
             true
           );
+
           pgRegisterGqlInputTypeByTypeId(
             arrayTablePgType.id,
             (_set, modifier) => {
@@ -604,6 +637,7 @@ export default (function PgTablesPlugin(
                 tablePgType.id,
                 modifier
               );
+
               if (RelevantTableInputType) {
                 return new GraphQLList(RelevantTableInputType);
               }
@@ -618,4 +652,4 @@ export default (function PgTablesPlugin(
     [],
     ["PgTypes"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/PgTypesPlugin.js b/packages/graphile-build-pg/src/plugins/PgTypesPlugin.ts
similarity index 98%
rename from packages/graphile-build-pg/src/plugins/PgTypesPlugin.js
rename to packages/graphile-build-pg/src/plugins/PgTypesPlugin.ts
index bdec8b7e6..77a822e3e 100644
--- a/packages/graphile-build-pg/src/plugins/PgTypesPlugin.js
+++ b/packages/graphile-build-pg/src/plugins/PgTypesPlugin.ts
@@ -1,5 +1,4 @@
-// @flow
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 
 import makeGraphQLJSONType from "../GraphQLJSON";
 
@@ -25,7 +24,7 @@ function parseInterval(str) {
   return result;
 }
 
-export default (function PgTypesPlugin(
+export default function PgTypesPlugin(
   builder,
   {
     pgExtendedTypes = true,
@@ -86,9 +85,11 @@ export default (function PgTypesPlugin(
       const gqlTypeByTypeIdAndModifier = {
         ...build.pgGqlTypeByTypeIdAndModifier,
       };
+
       const gqlInputTypeByTypeIdAndModifier = {
         ...build.pgGqlInputTypeByTypeIdAndModifier,
       };
+
       const isNull = val => val == null || val.__isNull;
       const pg2GqlMapper = {};
       const pg2gqlForType = type => {
@@ -128,6 +129,7 @@ export default (function PgTypesPlugin(
             "gql2pg should be called with three arguments, the third being the type modifier (or `null`); " +
               (stack || "")
           );
+
           // Hack for backwards compatibility:
           modifier = null;
         }
@@ -164,22 +166,27 @@ export default (function PgTypesPlugin(
               "A quantity of seconds. This is the only non-integer field, as all the other fields will dump their overflow into a smaller unit of time. Intervals don’t have a smaller unit than seconds.",
             type: GraphQLFloat,
           },
+
           minutes: {
             description: "A quantity of minutes.",
             type: GraphQLInt,
           },
+
           hours: {
             description: "A quantity of hours.",
             type: GraphQLInt,
           },
+
           days: {
             description: "A quantity of days.",
             type: GraphQLInt,
           },
+
           months: {
             description: "A quantity of months.",
             type: GraphQLInt,
           },
+
           years: {
             description: "A quantity of years.",
             type: GraphQLInt,
@@ -194,10 +201,12 @@ export default (function PgTypesPlugin(
             "An interval of time that has passed where the smallest distinct unit is a second.",
           fields: makeIntervalFields(),
         },
+
         {
           isIntervalType: true,
         }
       );
+
       addType(GQLInterval, "graphile-build-pg built-in");
 
       const GQLIntervalInput = newWithHooks(
@@ -208,10 +217,12 @@ export default (function PgTypesPlugin(
             "An interval of time that has passed where the smallest distinct unit is a second.",
           fields: makeIntervalFields(),
         },
+
         {
           isIntervalInputType: true,
         }
       );
+
       addType(GQLIntervalInput, "graphile-build-pg built-in");
 
       const stringType = (name, description) =>
@@ -232,10 +243,12 @@ export default (function PgTypesPlugin(
         inflection.builtin("BigFloat"),
         "A floating point number that requires more precision than IEEE 754 binary 64"
       );
+
       const BitString = stringType(
         inflection.builtin("BitString"),
         "A string representing a series of binary bits"
       );
+
       addType(BigFloat, "graphile-build-pg built-in");
       addType(BitString, "graphile-build-pg built-in");
 
@@ -245,7 +258,7 @@ export default (function PgTypesPlugin(
         1114, // timestamp
         1184, // timestamptz
         1083, // time
-        1266, // timetz
+        1266,
       ];
 
       const tweakToJson = fragment => fragment; // Since everything is to_json'd now, just pass through
@@ -299,6 +312,7 @@ export default (function PgTypesPlugin(
               type.namespaceName
             }.${type.name}")`
           );
+
           if (process.env.NODE_ENV === "test") {
             // This is to ensure that Graphile core does not introduce these problems
             throw error;
@@ -311,32 +325,36 @@ export default (function PgTypesPlugin(
         }
       };
       /*
-      Determined by running:
-
-        select oid, typname, typarray, typcategory, typtype from pg_catalog.pg_type where typtype = 'b' order by oid;
+       Determined by running:
+          select oid, typname, typarray, typcategory, typtype from pg_catalog.pg_type where typtype = 'b' order by oid;
+        We only need to add oidLookups for types that don't have the correct fallback
+       */
 
-      We only need to add oidLookups for types that don't have the correct fallback
-    */
       const SimpleDate = stringType(
         inflection.builtin("Date"),
         "The day, does not include a time."
       );
+
       const SimpleDatetime = stringType(
         inflection.builtin("Datetime"),
         "A point in time as described by the [ISO 8601](https://en.wikipedia.org/wiki/ISO_8601) standard. May or may not include a timezone."
       );
+
       const SimpleTime = stringType(
         inflection.builtin("Time"),
         "The exact time of day, does not include the date. May or may not have a timezone offset."
       );
+
       const SimpleJSON = stringType(
         inflection.builtin("JSON"),
         "A JavaScript object encoded in the JSON format as specified by [ECMA-404](http://www.ecma-international.org/publications/files/ECMA-ST/ECMA-404.pdf)."
       );
+
       const SimpleUUID = stringType(
         inflection.builtin("UUID"),
         "A universally unique identifier as defined by [RFC 4122](https://tools.ietf.org/html/rfc4122)."
       );
+
       const InetType = stringType(
         inflection.builtin("InternetAddress"),
         "An IPv4 or IPv6 host address, and optionally its subnet."
@@ -360,15 +378,18 @@ export default (function PgTypesPlugin(
             x: {
               type: new GraphQLNonNull(GraphQLFloat),
             },
+
             y: {
               type: new GraphQLNonNull(GraphQLFloat),
             },
           },
         },
+
         {
           isPointType: true,
         }
       );
+
       const PointInput = newWithHooks(
         GraphQLInputObjectType,
         {
@@ -377,11 +398,13 @@ export default (function PgTypesPlugin(
             x: {
               type: new GraphQLNonNull(GraphQLFloat),
             },
+
             y: {
               type: new GraphQLNonNull(GraphQLFloat),
             },
           },
         },
+
         {
           isPointInputType: true,
         }
@@ -398,7 +421,8 @@ export default (function PgTypesPlugin(
         "20": stringType(
           inflection.builtin("BigInt"),
           "A signed eight-byte integer. The upper big integer values are greater than the max value for a JavaScript number. Therefore all big integers will be output as strings and not numbers."
-        ), // bitint - even though this is int8, it's too big for JS int, so cast to string.
+        ),
+        // bitint - even though this is int8, it's too big for JS int, so cast to string.
         "21": GraphQLInt, // int2
         "23": GraphQLInt, // int4
         "700": GraphQLFloat, // float4
@@ -428,6 +452,7 @@ export default (function PgTypesPlugin(
 
         "869": InetType,
       };
+
       const oidInputLookup = {
         "1186": GQLIntervalInput, // interval
         "600": PointInput, // point
@@ -458,6 +483,7 @@ export default (function PgTypesPlugin(
             "months",
             "years",
           ];
+
           const parts = [];
           for (const key of keys) {
             if (o[key]) {
@@ -510,6 +536,7 @@ export default (function PgTypesPlugin(
               type.namespaceName
             }.${type.name}' (type=${type.type}):\n${indent(e.message)}`
           );
+
           // $FlowFixMe
           error.originalError = e;
           throw error;
@@ -559,9 +586,11 @@ export default (function PgTypesPlugin(
                 memo[inflection.enumName(value)] = {
                   value: value,
                 };
+
                 return memo;
               }, {}),
             },
+
             {
               pgIntrospection: type,
               isPgEnumType: true,
@@ -579,6 +608,7 @@ export default (function PgTypesPlugin(
             subtype.id,
             typeModifier
           );
+
           if (!gqlRangeSubType) {
             throw new Error("Range of unsupported");
           }
@@ -596,6 +626,7 @@ export default (function PgTypesPlugin(
                     description: "The value at one end of our range.",
                     type: new GraphQLNonNull(gqlRangeSubType),
                   },
+
                   inclusive: {
                     description:
                       "Whether or not the value of this bound is included in the range.",
@@ -603,6 +634,7 @@ export default (function PgTypesPlugin(
                   },
                 },
               },
+
               {
                 isPgRangeBoundType: true,
                 pgIntrospection: type,
@@ -610,6 +642,7 @@ export default (function PgTypesPlugin(
                 pgTypeModifier: typeModifier,
               }
             );
+
             const RangeBoundInput = newWithHooks(
               GraphQLInputObjectType,
               {
@@ -621,6 +654,7 @@ export default (function PgTypesPlugin(
                     description: "The value at one end of our range.",
                     type: new GraphQLNonNull(gqlRangeSubType),
                   },
+
                   inclusive: {
                     description:
                       "Whether or not the value of this bound is included in the range.",
@@ -628,6 +662,7 @@ export default (function PgTypesPlugin(
                   },
                 },
               },
+
               {
                 isPgRangeBoundInputType: true,
                 pgIntrospection: type,
@@ -635,6 +670,7 @@ export default (function PgTypesPlugin(
                 pgTypeModifier: typeModifier,
               }
             );
+
             Range = newWithHooks(
               GraphQLObjectType,
               {
@@ -645,12 +681,14 @@ export default (function PgTypesPlugin(
                     description: "The starting bound of our range.",
                     type: RangeBound,
                   },
+
                   end: {
                     description: "The ending bound of our range.",
                     type: RangeBound,
                   },
                 },
               },
+
               {
                 isPgRangeType: true,
                 pgIntrospection: type,
@@ -658,6 +696,7 @@ export default (function PgTypesPlugin(
                 pgTypeModifier: typeModifier,
               }
             );
+
             RangeInput = newWithHooks(
               GraphQLInputObjectType,
               {
@@ -668,12 +707,14 @@ export default (function PgTypesPlugin(
                     description: "The starting bound of our range.",
                     type: RangeBoundInput,
                   },
+
                   end: {
                     description: "The ending bound of our range.",
                     type: RangeBoundInput,
                   },
                 },
               },
+
               {
                 isPgRangeInputType: true,
                 pgIntrospection: type,
@@ -681,6 +722,7 @@ export default (function PgTypesPlugin(
                 pgTypeModifier: typeModifier,
               }
             );
+
             addType(Range, "graphile-build-pg built-in");
             addType(RangeInput, "graphile-build-pg built-in");
           } else {
@@ -749,10 +791,12 @@ end`;
             type.domainBaseTypeId,
             typeModifier
           );
+
           const baseInputType =
             gqlInputTypeByTypeIdAndModifier[type.domainBaseTypeId][
               typeModifierKey
             ];
+
           // Hack stolen from: https://github.com/graphile/postgraphile/blob/ade728ed8f8e3ecdc5fdad7d770c67aa573578eb/src/graphql/schema/type/aliasGqlType.ts#L16
           gqlTypeByTypeIdAndModifier[type.id][typeModifierKey] = Object.assign(
             Object.create(baseType),
@@ -761,6 +805,7 @@ end`;
               description: type.description,
             }
           );
+
           if (baseInputType && baseInputType !== baseType) {
             gqlInputTypeByTypeIdAndModifier[type.id][
               typeModifierKey
@@ -768,6 +813,7 @@ end`;
               name: inflection.inputType(
                 gqlTypeByTypeIdAndModifier[type.id][typeModifierKey]
               ),
+
               description: type.description,
             });
           }
@@ -782,6 +828,7 @@ end`;
             type.arrayItemTypeId,
             typeModifier
           );
+
           gqlTypeByTypeIdAndModifier[type.id][
             typeModifierKey
           ] = new GraphQLList(arrayEntryOutputType);
@@ -790,6 +837,7 @@ end`;
               type.arrayItemTypeId,
               typeModifier
             );
+
             if (arrayEntryInputType) {
               gqlInputTypeByTypeIdAndModifier[type.id][
                 typeModifierKey
@@ -833,6 +881,7 @@ end`;
         addType(
           getNamedType(gqlTypeByTypeIdAndModifier[type.id][typeModifierKey])
         );
+
         return gqlTypeByTypeIdAndModifier[type.id][typeModifierKey];
       };
 
@@ -852,6 +901,7 @@ end`;
           const type = introspectionResultsByKind.type.find(
             t => t.id === typeId
           );
+
           if (!type) {
             throw new Error(
               `Type '${typeId}' not present in introspection results`
@@ -1063,6 +1113,7 @@ end`;
     },
     ["PgTypesHstore"]
   );
+
   builder.hook(
     "build",
     build => {
@@ -1082,6 +1133,7 @@ end`;
       const hstoreExtension = introspectionResultsByKind.extension.find(
         e => e.name === "hstore"
       );
+
       if (!hstoreExtension) {
         return build;
       }
@@ -1091,6 +1143,7 @@ end`;
         t =>
           t.name === "hstore" && t.namespaceId === hstoreExtension.namespaceId
       );
+
       if (!hstoreType) {
         return build;
       }
@@ -1124,8 +1177,9 @@ end`;
     [],
     ["PgTypes"]
   );
+
   /* End of hstore type */
-}: Plugin);
+} as Plugin;
 
 function makeGraphQLHstoreType(graphql, hstoreTypeName) {
   const { GraphQLScalarType, Kind } = graphql;
@@ -1232,6 +1286,7 @@ function makeGraphQLHstoreType(graphql, hstoreTypeName) {
     parseValue: identityWithCheck,
     parseLiteral,
   });
+
   return GraphQLHStore;
 }
 
diff --git a/packages/graphile-build-pg/src/plugins/addStartEndCursor.js b/packages/graphile-build-pg/src/plugins/addStartEndCursor.ts
similarity index 78%
rename from packages/graphile-build-pg/src/plugins/addStartEndCursor.js
rename to packages/graphile-build-pg/src/plugins/addStartEndCursor.ts
index 60ccd6e4c..af0666405 100644
--- a/packages/graphile-build-pg/src/plugins/addStartEndCursor.js
+++ b/packages/graphile-build-pg/src/plugins/addStartEndCursor.ts
@@ -1,12 +1,11 @@
-// @flow
-import type { Plugin } from "graphile-build";
+import { Plugin } from "graphile-build";
 const base64 = str => Buffer.from(String(str)).toString("base64");
 
 function cursorify(val) {
   return val && val.__cursor ? base64(JSON.stringify(val.__cursor)) : null;
 }
 
-export default (function addStartEndCursor(value) {
+export default function addStartEndCursor(value) {
   const data = value && value.data && value.data.length ? value.data : null;
   const startCursor = cursorify(data && data[0]);
   const endCursor = cursorify(data && data[value.data.length - 1]);
@@ -15,4 +14,4 @@ export default (function addStartEndCursor(value) {
     startCursor,
     endCursor,
   };
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build-pg/src/plugins/debugSql.js b/packages/graphile-build-pg/src/plugins/debugSql.ts
similarity index 99%
rename from packages/graphile-build-pg/src/plugins/debugSql.js
rename to packages/graphile-build-pg/src/plugins/debugSql.ts
index db667a59e..5da18feed 100644
--- a/packages/graphile-build-pg/src/plugins/debugSql.js
+++ b/packages/graphile-build-pg/src/plugins/debugSql.ts
@@ -13,6 +13,7 @@ export function formatSQLForDebugging(sql) {
     chalk.white,
     chalk.black,
   ];
+
   function nextColor() {
     colourIndex = (colourIndex + 1) % allowedColours.length;
     return allowedColours[colourIndex];
diff --git a/packages/graphile-build-pg/src/plugins/introspectionQuery.js b/packages/graphile-build-pg/src/plugins/introspectionQuery.ts
similarity index 99%
rename from packages/graphile-build-pg/src/plugins/introspectionQuery.js
rename to packages/graphile-build-pg/src/plugins/introspectionQuery.ts
index 93558d933..a7ad8a016 100644
--- a/packages/graphile-build-pg/src/plugins/introspectionQuery.js
+++ b/packages/graphile-build-pg/src/plugins/introspectionQuery.ts
@@ -1,4 +1,3 @@
-// @flow
 /*
  * IMPORTANT: when editing this file, ensure all operators (e.g. `@>`) are
  * specified in the correct namespace (e.g. `operator(pg_catalog.@>)`). It looks
diff --git a/packages/graphile-build-pg/src/plugins/makeProcField.js b/packages/graphile-build-pg/src/plugins/makeProcField.ts
similarity index 98%
rename from packages/graphile-build-pg/src/plugins/makeProcField.js
rename to packages/graphile-build-pg/src/plugins/makeProcField.ts
index f1fb0a62b..0ffc2018f 100644
--- a/packages/graphile-build-pg/src/plugins/makeProcField.js
+++ b/packages/graphile-build-pg/src/plugins/makeProcField.ts
@@ -1,10 +1,9 @@
-// @flow
 const nullableIf = (GraphQLNonNull, condition, Type) =>
   condition ? Type : new GraphQLNonNull(Type);
 
-import type { Build, FieldWithHooksFunction } from "graphile-build";
-import type { PgProc } from "./PgIntrospectionPlugin";
-import type { SQL } from "pg-sql2";
+import { Build, FieldWithHooksFunction } from "graphile-build";
+import { PgProc } from "./PgIntrospectionPlugin";
+import { SQL } from "pg-sql2";
 import debugSql from "./debugSql";
 import chalk from "chalk";
 
@@ -21,17 +20,17 @@ const firstValue = obj => {
 export default function makeProcField(
   fieldName: string,
   proc: PgProc,
-  build: {| ...Build |},
+  build: Build,
   {
     fieldWithHooks,
     computed = false,
     isMutation = false,
     forceList = false,
   }: {
-    fieldWithHooks: FieldWithHooksFunction,
-    computed?: boolean,
-    isMutation?: boolean,
-    forceList?: boolean,
+    fieldWithHooks: FieldWithHooksFunction;
+    computed?: boolean;
+    isMutation?: boolean;
+    forceList?: boolean;
   }
 ) {
   const {
@@ -57,6 +56,7 @@ export default function makeProcField(
       getNamedType,
       isCompositeType,
     },
+
     inflection,
     pgQueryFromResolveData: queryFromResolveData,
     pgAddStartEndCursor: addStartEndCursor,
@@ -68,6 +68,7 @@ export default function makeProcField(
       subscriptions = false,
       pgForbidSetofFunctionsToReturnNull = false,
     },
+
     pgPrepareAndRun,
   } = build;
 
@@ -100,8 +101,9 @@ export default function makeProcField(
   const argModesWithOutput = [
     "o", // OUT,
     "b", // INOUT
-    "t", // TABLE
+    "t",
   ];
+
   const outputArgNames = proc.argTypeIds.reduce((prev, _, idx) => {
     if (argModesWithOutput.includes(proc.argModes[idx])) {
       prev.push(proc.argNames[idx] || "");
@@ -202,6 +204,7 @@ export default function makeProcField(
         const ConnectionType = getTypeByName(
           inflection.connection(TableType.name)
         );
+
         if (!ConnectionType) {
           throw new Error(
             `Do not have a connection type '${inflection.connection(
@@ -242,6 +245,7 @@ export default function makeProcField(
         const ConnectionType = getTypeByName(
           inflection.recordFunctionConnection(proc)
         );
+
         if (!ConnectionType) {
           throw new Error(
             `Do not have a connection type '${inflection.recordFunctionConnection(
@@ -365,6 +369,7 @@ export default function makeProcField(
           parsedResolveInfoFragment,
           ReturnType
         );
+
         const isConnection = !forceList && !isMutation && proc.returnsSet;
         const query = queryFromResolveData(
           sqlMutationQuery,
@@ -389,6 +394,7 @@ export default function makeProcField(
               !rawReturnType.isPgArray &&
               (isTableLike || isRecordLike),
           },
+
           innerQueryBuilder => {
             innerQueryBuilder.parentQueryBuilder = parentQueryBuilder;
             if (!isTableLike) {
@@ -400,6 +406,7 @@ export default function makeProcField(
                     null,
                     resolveData
                   ),
+
                   "value"
                 );
               } else {
@@ -410,6 +417,7 @@ export default function makeProcField(
                     null, // We can't determine a type modifier for functions
                     resolveData
                   ),
+
                   "value"
                 );
               }
@@ -427,6 +435,7 @@ export default function makeProcField(
             ? parentQueryBuilder.rootValue
             : resolveInfo && resolveInfo.rootValue
         );
+
         return query;
       }
       if (computed) {
@@ -443,6 +452,7 @@ export default function makeProcField(
                     implicitArgs: [parentTableAlias],
                   }
                 );
+
                 const query = makeQuery(
                   parsedResolveInfoFragment,
                   ReturnType,
@@ -450,6 +460,7 @@ export default function makeProcField(
                   functionAlias,
                   queryBuilder
                 );
+
                 return sql.fragment`(${query})`;
               }, getSafeAliasFromAlias(parsedResolveInfoFragment.alias));
             },
@@ -464,6 +475,7 @@ export default function makeProcField(
         memo[gqlArgName] = {
           type: argGqlTypes[argIndex],
         };
+
         return memo;
       }, {});
       if (isMutation) {
@@ -473,6 +485,7 @@ export default function makeProcField(
           proc.returnsSet || rawReturnType.isPgArray,
           outputArgNames
         );
+
         const isNotVoid = String(returnType.id) !== "2278";
         // If set then plural name
         PayloadType = newWithHooks(
@@ -490,6 +503,7 @@ export default function makeProcField(
                     type: GraphQLString,
                   },
                 },
+
                 isNotVoid
                   ? {
                       [resultFieldName]: pgField(
@@ -506,18 +520,21 @@ export default function makeProcField(
                               }
                             : null),
                         },
+
                         {},
                         false,
                         {
                           pgType: returnType,
                         }
                       ),
+
                       // Result
                     }
                   : null
               );
             },
           },
+
           {
             __origin: `Adding mutation function payload type for ${describePgEntity(
               proc
@@ -531,6 +548,7 @@ export default function makeProcField(
             ...payloadTypeScope,
           }
         );
+
         ReturnType = PayloadType;
         const InputType = newWithHooks(
           GraphQLInputObjectType,
@@ -543,9 +561,11 @@ export default function makeProcField(
               clientMutationId: {
                 type: GraphQLString,
               },
+
               ...args,
             },
           },
+
           {
             __origin: `Adding mutation function input type for ${describePgEntity(
               proc
@@ -558,6 +578,7 @@ export default function makeProcField(
             isMutationInput: true,
           }
         );
+
         args = {
           input: {
             type: new GraphQLNonNull(InputType),
@@ -664,6 +685,7 @@ export default function makeProcField(
                   resolveContext,
                   resolveInfo
                 );
+
                 const intermediateIdentifier = sql.identifier(Symbol());
                 const isVoid = returnType.id === "2278";
                 const isPgRecord = returnType.id === "2249";
@@ -680,6 +702,7 @@ export default function makeProcField(
                           returnType.namespaceName,
                           returnType.name
                         ),
+
                     sql.query`select ${
                       isPgClass
                         ? sql.query`${intermediateIdentifier}.*`
@@ -697,11 +720,13 @@ export default function makeProcField(
                         }
                       : null
                   );
+
                   await pgClient.query("RELEASE SAVEPOINT graphql_mutation");
                 } catch (e) {
                   await pgClient.query(
                     "ROLLBACK TO SAVEPOINT graphql_mutation"
                   );
+
                   throw e;
                 }
               } else {
@@ -714,6 +739,7 @@ export default function makeProcField(
                   resolveContext,
                   resolveInfo
                 );
+
                 const { text, values } = sql.compile(query);
                 if (debugSql.enabled) debugSql(text);
                 const queryResult = await pgPrepareAndRun(
@@ -721,6 +747,7 @@ export default function makeProcField(
                   text,
                   values
                 );
+
                 queryResultRows = queryResult.rows;
               }
               const rows = queryResultRows;
diff --git a/packages/graphile-build-pg/src/plugins/pgField.js b/packages/graphile-build-pg/src/plugins/pgField.ts
similarity index 99%
rename from packages/graphile-build-pg/src/plugins/pgField.js
rename to packages/graphile-build-pg/src/plugins/pgField.ts
index d4b2e5a17..f3b4f4f9a 100644
--- a/packages/graphile-build-pg/src/plugins/pgField.js
+++ b/packages/graphile-build-pg/src/plugins/pgField.ts
@@ -42,10 +42,12 @@ export default function pgField(
         const safeAlias = getSafeAliasFromAlias(
           parsedResolveInfoFragment.alias
         );
+
         const resolveData = getDataFromParsedResolveInfoFragment(
           parsedResolveInfoFragment,
           FieldType
         );
+
         return {
           ...(options.hoistCursor &&
           resolveData.usesCursor &&
@@ -83,6 +85,7 @@ export default function pgField(
                 queryBuilder.context,
                 queryBuilder.rootValue
               );
+
               return sql.fragment`(${query})`;
             }, safeAlias);
           },
diff --git a/packages/graphile-build-pg/src/plugins/viaTemporaryTable.js b/packages/graphile-build-pg/src/plugins/viaTemporaryTable.ts
similarity index 95%
rename from packages/graphile-build-pg/src/plugins/viaTemporaryTable.js
rename to packages/graphile-build-pg/src/plugins/viaTemporaryTable.ts
index 456e8316e..738f805b4 100644
--- a/packages/graphile-build-pg/src/plugins/viaTemporaryTable.js
+++ b/packages/graphile-build-pg/src/plugins/viaTemporaryTable.ts
@@ -1,8 +1,6 @@
-// @flow
-
 import * as sql from "pg-sql2";
-import type { Client } from "pg";
-import type { SQL, SQLQuery } from "pg-sql2";
+import { Client } from "pg";
+import { SQL, SQLQuery } from "pg-sql2";
 import debugSql from "./debugSql";
 
 /*
@@ -37,16 +35,19 @@ import debugSql from "./debugSql";
 
 export default async function viaTemporaryTable(
   pgClient: Client,
-  sqlTypeIdentifier: ?SQL,
+  sqlTypeIdentifier: SQL | null | undefined,
   sqlMutationQuery: SQL,
   sqlResultSourceAlias: SQL,
   sqlResultQuery: SQL,
   isPgClassLike: boolean = true,
-  pgRecordInfo: ?{
-    // eslint-disable-next-line flowtype/no-weak-types
-    outputArgTypes: Array<any>,
-    outputArgNames: Array<string>,
-  } = undefined
+  pgRecordInfo:
+    | {
+        // eslint-disable-next-line flowtype/no-weak-types
+        outputArgTypes: Array<any>;
+        outputArgNames: Array<string>;
+      }
+    | null
+    | undefined = undefined
 ) {
   const isPgRecord = pgRecordInfo != null;
   const { outputArgTypes, outputArgNames } = pgRecordInfo || {};
@@ -64,6 +65,7 @@ export default async function viaTemporaryTable(
       pgClient,
       sql.query`with ${sqlResultSourceAlias} as (${sqlMutationQuery}) ${sqlResultQuery}`
     );
+
     return rows;
   } else {
     /*
@@ -97,6 +99,7 @@ export default async function viaTemporaryTable(
                 outputArgName !== "" ? outputArgName : `column${idx + 1}`
               )}::text`
           ),
+
           " ,"
         )}]`
       : sql.query`(${sqlResultSourceAlias}.${sqlResultSourceAlias})::${sqlTypeIdentifier}`;
@@ -104,6 +107,7 @@ export default async function viaTemporaryTable(
       pgClient,
       sql.query`with ${sqlResultSourceAlias} as (${sqlMutationQuery}) select (${selectionField})::text from ${sqlResultSourceAlias}`
     );
+
     const { rows } = result;
     const firstNonNullRow = rows.find(row => row !== null);
     // TODO: we should be able to have `pg` not interpret the results as
@@ -134,6 +138,7 @@ select ${sql.join(
                 outputArgName !== "" ? outputArgName : `column${idx + 1}`
               )}`
           ),
+
           ", "
         )}
 from (values ${sql.join(
@@ -159,6 +164,7 @@ from unnest((${sql.value(values)})::text[]) str`;
        */
       rawValue === null ? { __isNull: true } : filteredValuesResults.shift()
     );
+
     return finalRows;
   }
 }
diff --git a/packages/graphile-build-pg/src/queryFromResolveDataFactory.js b/packages/graphile-build-pg/src/queryFromResolveDataFactory.ts
similarity index 96%
rename from packages/graphile-build-pg/src/queryFromResolveDataFactory.js
rename to packages/graphile-build-pg/src/queryFromResolveDataFactory.ts
index ebd3d8f4d..bd4dce40a 100644
--- a/packages/graphile-build-pg/src/queryFromResolveDataFactory.js
+++ b/packages/graphile-build-pg/src/queryFromResolveDataFactory.ts
@@ -1,10 +1,9 @@
-// @flow
 import QueryBuilder from "./QueryBuilder";
-import type QueryBuilderOptions from "./QueryBuilder";
-import type { RawAlias } from "./QueryBuilder";
+import QueryBuilderOptions from "./QueryBuilder";
+import { RawAlias } from "./QueryBuilder";
 import * as sql from "pg-sql2";
-import type { SQL } from "pg-sql2";
-import type { DataForType } from "graphile-build";
+import { SQL } from "pg-sql2";
+import { DataForType } from "graphile-build";
 import isSafeInteger from "lodash/isSafeInteger";
 import assert from "assert";
 
@@ -16,20 +15,20 @@ const identity = _ => _ !== null && _ !== undefined;
 // $FlowFixMe
 export default (queryBuilderOptions: QueryBuilderOptions = {}) => (
   from: SQL,
-  fromAlias: ?SQL,
+  fromAlias: SQL | null | undefined,
   resolveData: DataForType,
   inOptions: {
-    withPagination?: boolean,
-    withPaginationAsFields?: boolean,
-    asJson?: boolean,
-    asJsonAggregate?: boolean,
-    addNullCase?: boolean,
-    addNotDistinctFromNullCase?: boolean,
-    onlyJsonField?: boolean,
-    useAsterisk?: boolean,
+    withPagination?: boolean;
+    withPaginationAsFields?: boolean;
+    asJson?: boolean;
+    asJsonAggregate?: boolean;
+    addNullCase?: boolean;
+    addNotDistinctFromNullCase?: boolean;
+    onlyJsonField?: boolean;
+    useAsterisk?: boolean;
   },
-  // TODO:v5: context is not optional
-  withBuilder?: ((builder: QueryBuilder) => void) | null | void,
+
+  withBuilder?: ((builder: QueryBuilder) => undefined) | null | undefined,
   context?: GraphQLContext = {},
   rootValue?: any // eslint-disable-line flowtype/no-weak-types
 ) => {
@@ -67,6 +66,7 @@ export default (queryBuilderOptions: QueryBuilderOptions = {}) => (
     context,
     rootValue
   );
+
   queryBuilder.from(from, fromAlias ? fromAlias : undefined);
 
   if (withBuilder) {
@@ -293,6 +293,7 @@ exists(
               ...getPgCursorPrefix(),
               sql.fragment`json_build_array(${sql.join(orderBy, ", ")})`,
             ],
+
             ", "
           )})`;
         } else {
@@ -409,6 +410,7 @@ OR\
           queryHasFirst,
           queryBuilder.getFinalOffset() || 0
         );
+
     const hasPreviousPage = queryHasZeroLimit
       ? sql.literal(false)
       : generateNextPrevPageSql(
@@ -430,6 +432,7 @@ OR\
         sql.fragment`coalesce((select ${sqlSummaryAlias}.data from ${sqlSummaryAlias}), '[]'::json)`,
         "data",
       ]);
+
       if (calculateHasNextPage) {
         fields.push([hasNextPage, "hasNextPage"]);
       }
@@ -444,6 +447,7 @@ OR\
         context,
         rootValue
       );
+
       aggregateQueryBuilder.from(
         queryBuilder.getTableExpression(),
         queryBuilder.getTableAlias()
@@ -455,6 +459,7 @@ OR\
       const aggregateJsonBuildObject = aggregateQueryBuilder.build({
         onlyJsonField: true,
       });
+
       const aggregatesSql = sql.fragment`\
 (
   select ${aggregateJsonBuildObject}
@@ -468,6 +473,7 @@ OR\
         fields.map(
           ([expr, alias]) => sql.fragment`${expr} as ${sql.identifier(alias)}`
         ),
+
         ", "
       )} ${sqlFrom}`;
     } else {
diff --git a/packages/graphile-build-pg/src/utils.js b/packages/graphile-build-pg/src/utils.ts
similarity index 98%
rename from packages/graphile-build-pg/src/utils.js
rename to packages/graphile-build-pg/src/utils.ts
index 5cdd16d00..e545331cd 100644
--- a/packages/graphile-build-pg/src/utils.js
+++ b/packages/graphile-build-pg/src/utils.ts
@@ -1,4 +1,3 @@
-// @flow
 export const parseTags = (str: string) => {
   return str.split(/\r?\n/).reduce(
     (prev, curr) => {
diff --git a/packages/graphile-build-pg/src/withPgClient.js b/packages/graphile-build-pg/src/withPgClient.ts
similarity index 91%
rename from packages/graphile-build-pg/src/withPgClient.js
rename to packages/graphile-build-pg/src/withPgClient.ts
index 397b6fede..29d8b442c 100644
--- a/packages/graphile-build-pg/src/withPgClient.js
+++ b/packages/graphile-build-pg/src/withPgClient.ts
@@ -1,4 +1,3 @@
-// @flow
 import pg from "pg";
 import debugFactory from "debug";
 
@@ -10,7 +9,7 @@ function constructorName(obj) {
 
 // Some duck-typing
 
-function quacksLikePgClient(pgConfig: mixed): boolean {
+function quacksLikePgClient(pgConfig: unknown): boolean {
   // A diagnosis of exclusion
   if (!pgConfig || typeof pgConfig !== "object") return false;
   if (constructorName(pgConfig) !== "Client") return false;
@@ -21,7 +20,7 @@ function quacksLikePgClient(pgConfig: mixed): boolean {
   return true;
 }
 
-export function quacksLikePgPool(pgConfig: mixed): boolean {
+export function quacksLikePgPool(pgConfig: unknown): boolean {
   // A diagnosis of exclusion
   if (!pgConfig || typeof pgConfig !== "object") return false;
   if (
@@ -44,14 +43,14 @@ export const getPgClientAndReleaserFromConfig = async (
   let releasePgClient = () => {};
   let pgClient: pg.Client;
   if (pgConfig instanceof pg.Client || quacksLikePgClient(pgConfig)) {
-    pgClient = (pgConfig: pg.Client);
+    pgClient = pgConfig as pg.Client;
     if (!pgClient.release) {
       throw new Error(
         "We only support PG clients from a PG pool (because otherwise the `await` call can hang indefinitely if an error occurs and there's no error handler)"
       );
     }
   } else if (pgConfig instanceof pg.Pool || quacksLikePgPool(pgConfig)) {
-    const pgPool = (pgConfig: pg.Pool);
+    const pgPool = pgConfig as pg.Pool;
     pgClient = await pgPool.connect();
     releasePgClient = () => pgClient.release();
   } else if (pgConfig === undefined || typeof pgConfig === "string") {
@@ -63,6 +62,7 @@ export const getPgClientAndReleaserFromConfig = async (
       new Promise((resolve, reject) =>
         pgClient.end(err => (err ? reject(err) : resolve()))
       );
+
     await new Promise((resolve, reject) =>
       pgClient.connect(err => (err ? reject(err) : resolve()))
     );
@@ -75,8 +75,8 @@ export const getPgClientAndReleaserFromConfig = async (
 };
 
 const withPgClient = async (
-  pgConfig: pg.Client | pg.Pool | string | void,
-  fn: (pgClient: pg.Client) => *
+  pgConfig: pg.Client | pg.Pool | string | undefined,
+  fn: (pgClient: pg.Client) => any
 ) => {
   if (!fn) {
     throw new Error("Nothing to do!");
@@ -84,6 +84,7 @@ const withPgClient = async (
   const { pgClient, releasePgClient } = await getPgClientAndReleaserFromConfig(
     pgConfig
   );
+
   const errorHandler = e => {
     // eslint-disable-next-line no-console
     console.error("withPgClient client error:", e.message);
diff --git a/packages/graphile-build/src/Live.d.ts b/packages/graphile-build/src/Live.d.ts
index 6bc97edb5..8495aa4f4 100644
--- a/packages/graphile-build/src/Live.d.ts
+++ b/packages/graphile-build/src/Live.d.ts
@@ -41,12 +41,15 @@ export abstract class LiveProvider {
 export class LiveMonitor {
   providers: { [namespace: string]: LiveProvider };
   subscriptionReleasersByCounter: {
-    [counter: string]: (() => void)[],
+    [counter: string]: (() => void)[];
   };
   liveConditionsByCounter: { [counter: string]: Array<PredicateGenerator> };
   changeCounter: number;
 
-  constructor(providers: { [namespace: string]: LiveProvider }, extraRootValue: any);
+  constructor(
+    providers: { [namespace: string]: LiveProvider },
+    extraRootValue: any
+  );
 
   resetBefore(currentCounter: number): void;
   release(): void;
diff --git a/packages/graphile-build/src/Live.js b/packages/graphile-build/src/Live.ts
similarity index 96%
rename from packages/graphile-build/src/Live.js
rename to packages/graphile-build/src/Live.ts
index 9f6f93ed2..dfe93a8db 100644
--- a/packages/graphile-build/src/Live.js
+++ b/packages/graphile-build/src/Live.ts
@@ -1,11 +1,10 @@
-// @flow
 /* eslint-disable flowtype/no-weak-types */
 import callbackToAsyncIterator from "./callbackToAsyncIterator";
-import type { GraphQLResolveInfo } from "graphql";
+import { GraphQLResolveInfo } from "graphql";
 import { throttle } from "lodash";
 
-type SubscriptionReleaser = () => void;
-type SubscriptionCallback = () => void;
+type SubscriptionReleaser = () => undefined;
+type SubscriptionCallback = () => undefined;
 
 type Predicate = (record: any) => boolean;
 type PredicateGenerator = (data: any) => Predicate;
@@ -78,10 +77,11 @@ export class LiveMonitor {
   released: boolean;
   providers: { [namespace: string]: LiveProvider };
   subscriptionReleasersByCounter: {
-    [counter: string]: (() => void)[],
+    [counter: string]: () => undefined[];
   };
+
   liveConditionsByCounter: { [counter: string]: Array<PredicateGenerator> };
-  changeCallback: ((arg: any) => void) | null;
+  changeCallback: ((arg: any) => undefined) | null;
   changeCounter: number;
   extraRootValue: any;
 
@@ -107,6 +107,7 @@ export class LiveMonitor {
         trailing: true,
       }
     );
+
     if (!this._reallyHandleChange) {
       throw new Error("This is just to make flow happy");
     }
@@ -118,6 +119,7 @@ export class LiveMonitor {
         trailing: true,
       }
     );
+
     this.onChange = this.onChange.bind(this);
   }
 
@@ -141,6 +143,7 @@ export class LiveMonitor {
       const oldCounters = Object.keys(this.liveConditionsByCounter).filter(
         n => parseInt(n, 10) < currentCounter
       );
+
       for (const oldCounter of oldCounters) {
         delete this.liveConditionsByCounter[oldCounter];
       }
@@ -162,7 +165,7 @@ export class LiveMonitor {
   }
 
   // Tell Flow that we're okay with overwriting this
-  handleChange: (() => void) | null;
+  handleChange: (() => undefined) | null;
   handleChange() {
     /* This function is throttled to ~25ms (see constructor); it's purpose is
      * to bundle up all the changes that occur in a small window into the same
@@ -177,7 +180,7 @@ export class LiveMonitor {
   }
 
   // Tell Flow that we're okay with overwriting this
-  _reallyHandleChange: (() => void) | null;
+  _reallyHandleChange: (() => undefined) | null;
   _reallyHandleChange() {
     // This function is throttled to MONITOR_THROTTLE_DURATION (see constructor)
     if (this.changeCallback) {
@@ -204,6 +207,7 @@ export class LiveMonitor {
           this.resetBefore(counter);
         },
       };
+
       cb(changeRootValue);
     } else {
       // eslint-disable-next-line no-console
@@ -212,8 +216,8 @@ export class LiveMonitor {
   }
 
   // Tell Flow that we're okay with overwriting this
-  onChange: (callback: () => void) => void;
-  onChange(callback: () => void) {
+  onChange: (callback: () => undefined) => undefined;
+  onChange(callback: () => undefined) {
     if (this.released) {
       throw new Error("Monitors cannot be reused.");
     }
@@ -256,6 +260,7 @@ export class LiveMonitor {
         collectionIdentifier,
         predicate
       );
+
       if (releaser) {
         this.subscriptionReleasersByCounter[String(counter)].push(releaser);
       }
@@ -293,6 +298,7 @@ export class LiveMonitor {
         collectionIdentifier,
         recordIdentifier
       );
+
       if (releaser) {
         this.subscriptionReleasersByCounter[String(counter)].push(releaser);
       }
@@ -327,6 +333,7 @@ export class LiveCoordinator {
       console.warn(
         `LiveProvider '${namespace}' is not registered, skipping live source.`
       );
+
       return;
     }
     this.providers[namespace].registerSource(source);
@@ -354,6 +361,7 @@ export class LiveCoordinator {
         if (iterator) iterator.throw(e);
       },
     });
+
     const iterator = makeAsyncIteratorFromMonitor(monitor);
     return iterator;
   }
diff --git a/packages/graphile-build/src/SchemaBuilder.js b/packages/graphile-build/src/SchemaBuilder.ts
similarity index 84%
rename from packages/graphile-build/src/SchemaBuilder.js
rename to packages/graphile-build/src/SchemaBuilder.ts
index b38dd9bdf..e7aaee07c 100644
--- a/packages/graphile-build/src/SchemaBuilder.js
+++ b/packages/graphile-build/src/SchemaBuilder.ts
@@ -1,9 +1,8 @@
-// @flow
 import debugFactory from "debug";
 import makeNewBuild from "./makeNewBuild";
 import { bindAll } from "./utils";
 import * as graphql from "graphql";
-import type {
+import {
   GraphQLType,
   GraphQLNamedType,
   GraphQLInterfaceType,
@@ -12,14 +11,14 @@ import type {
 import EventEmitter from "events";
 // TODO: when we move to TypeScript, change this to:
 // import { EventEmitter } from "events";
-import type {
+import {
   simplifyParsedResolveInfoFragmentWithType,
   parseResolveInfo,
 } from "graphql-parse-resolve-info";
-import type { GraphQLResolveInfo } from "graphql/type/definition";
-import type resolveNode from "./resolveNode";
+import { GraphQLResolveInfo } from "graphql/type/definition";
+import resolveNode from "./resolveNode";
 
-import type { FieldWithHooksFunction } from "./makeNewBuild";
+import { FieldWithHooksFunction } from "./makeNewBuild";
 const { GraphQLSchema } = graphql;
 
 const debug = debugFactory("graphile-builder");
@@ -27,123 +26,130 @@ const debug = debugFactory("graphile-builder");
 const INDENT = "  ";
 
 export type Options = {
-  [string]: mixed,
+  [a: string]: unknown;
 };
 
 export type Plugin = (
   builder: SchemaBuilder,
   options: Options
-) => Promise<void> | void;
+) => Promise<undefined> | undefined;
 
-type TriggerChangeType = () => void;
+type TriggerChangeType = () => undefined;
 
 export type DataForType = {
-  [string]: Array<mixed>,
+  [a: string]: Array<unknown>;
 };
 
-export type Build = {|
-  graphileBuildVersion: string,
-  graphql: *,
-  parseResolveInfo: parseResolveInfo,
-  simplifyParsedResolveInfoFragmentWithType: simplifyParsedResolveInfoFragmentWithType,
+export type Build = {
+  graphileBuildVersion: string;
+  graphql: any;
+  parseResolveInfo: parseResolveInfo;
+  simplifyParsedResolveInfoFragmentWithType: simplifyParsedResolveInfoFragmentWithType;
   // DEPRECATED: getAliasFromResolveInfo: (resolveInfo: GraphQLResolveInfo) => string,
-  getSafeAliasFromResolveInfo: (resolveInfo: GraphQLResolveInfo) => string,
-  getSafeAliasFromAlias: (alias: string) => string,
-  resolveAlias(
+  getSafeAliasFromResolveInfo: (resolveInfo: GraphQLResolveInfo) => string;
+  getSafeAliasFromAlias: (alias: string) => string;
+  resolveAlias: (
     data: {},
-    _args: mixed,
-    _context: mixed,
+    _args: unknown,
+    _context: unknown,
     resolveInfo: GraphQLResolveInfo
-  ): string,
-  addType(type: GraphQLNamedType, origin?: ?string): void,
-  getTypeByName(typeName: string): ?GraphQLType,
-  extend<Obj1: *, Obj2: *>(base: Obj1, extra: Obj2, hint?: string): Obj1 & Obj2,
-  newWithHooks<T: GraphQLNamedType | GraphQLSchema, ConfigType: *>(
-    Class<T>,
+  ) => string;
+  addType: (
+    type: GraphQLNamedType,
+    origin: string | null | undefined
+  ) => undefined;
+  getTypeByName: (typeName: string) => GraphQLType | null | undefined;
+  extend: <Obj1 extends any, Obj2 extends any>(
+    base: Obj1,
+    extra: Obj2,
+    hint: string
+  ) => Obj1 & Obj2;
+  newWithHooks: <
+    T extends GraphQLNamedType | GraphQLSchema,
+    ConfigType extends any
+  >(
+    a: Class<T>,
     spec: ConfigType,
     scope: Scope,
-    performNonEmptyFieldsCheck?: boolean
-  ): ?T,
-  fieldDataGeneratorsByType: Map<*, *>, // @deprecated - use fieldDataGeneratorsByFieldNameByType instead
-  fieldDataGeneratorsByFieldNameByType: Map<*, *>,
-  fieldArgDataGeneratorsByFieldNameByType: Map<*, *>,
+    performNonEmptyFieldsCheck: boolean
+  ) => T | null | undefined;
+  fieldDataGeneratorsByType: Map<any, any>; // @deprecated - use fieldDataGeneratorsByFieldNameByType instead
+  fieldDataGeneratorsByFieldNameByType: Map<any, any>;
+  fieldArgDataGeneratorsByFieldNameByType: Map<any, any>;
   inflection: {
     // eslint-disable-next-line flowtype/no-weak-types
-    [string]: (...args: Array<any>) => string,
-  },
-  swallowError: (e: Error) => void,
+    [a: string]: (...args: Array<any>) => string;
+  };
+
+  swallowError: (e: Error) => undefined;
   // resolveNode: EXPERIMENTAL, API might change!
-  resolveNode: resolveNode,
+  resolveNode: resolveNode;
   status: {
-    currentHookName: ?string,
-    currentHookEvent: ?string,
-  },
-  scopeByType: Map<GraphQLType, Scope>,
-|};
+    currentHookName: string | null | undefined;
+    currentHookEvent: string | null | undefined;
+  };
+
+  scopeByType: Map<GraphQLType, Scope>;
+};
 
-export type BuildExtensionQuery = {|
-  $$isQuery: Symbol,
-|};
+export type BuildExtensionQuery = {
+  $$isQuery: Symbol;
+};
 
 export type Scope = {
-  __origin: ?string,
-  [string]: mixed,
+  __origin: string | null | undefined;
+  [a: string]: unknown;
 };
 
-export type Context = {|
-  scope: Scope,
-  type: string,
-  [string]: mixed,
-|};
+export type Context = {
+  scope: Scope;
+  type: string;
+  [a: string]: unknown;
+};
 
 type DataGeneratorFunction = () => {};
 
-export type ContextGraphQLObjectTypeFields = {|
+export type ContextGraphQLObjectTypeFields = {
   addDataGeneratorForField: (
     fieldName: string,
     fn: DataGeneratorFunction
-  ) => void,
-  recurseDataGeneratorsForField: (fieldName: string) => void, // @deprecated - DO NOT USE!
-  Self: GraphQLNamedType,
-  GraphQLObjectType: GraphQLObjectTypeConfig<*, *>,
-  fieldWithHooks: FieldWithHooksFunction,
-|};
+  ) => undefined;
+  recurseDataGeneratorsForField: (fieldName: string) => undefined; // @deprecated - DO NOT USE!
+  Self: GraphQLNamedType;
+  GraphQLObjectType: GraphQLObjectTypeConfig<any, any>;
+  fieldWithHooks: FieldWithHooksFunction;
+};
 
 type SupportedHookTypes = {} | Build | Array<GraphQLInterfaceType>;
 
 export type Hook<
-  Type: SupportedHookTypes,
-  BuildExtensions: *,
-  ContextExtensions: *
+  Type extends SupportedHookTypes,
+  BuildExtensions extends any,
+  ContextExtensions extends any
 > = {
-  (
-    input: Type,
-    build: { ...Build, ...BuildExtensions },
-    context: { ...Context, ...ContextExtensions }
-  ): Type,
-  displayName?: string,
-  provides?: Array<string>,
-  before?: Array<string>,
-  after?: Array<string>,
+  displayName?: string;
+  provides?: Array<string>;
+  before?: Array<string>;
+  after?: Array<string>;
 };
 
-export type WatchUnwatch = (triggerChange: TriggerChangeType) => void;
+export type WatchUnwatch = (triggerChange: TriggerChangeType) => undefined;
 
-export type SchemaListener = (newSchema: GraphQLSchema) => void;
+export type SchemaListener = (newSchema: GraphQLSchema) => undefined;
 
 class SchemaBuilder extends EventEmitter {
   options: Options;
   watchers: Array<WatchUnwatch>;
   unwatchers: Array<WatchUnwatch>;
-  triggerChange: ?TriggerChangeType;
+  triggerChange: TriggerChangeType | null | undefined;
   depth: number;
   hooks: {
-    [string]: Array<Hook<*, *, *>>,
+    [a: string]: Array<Hook<any, any, any>>;
   };
 
-  _currentPluginName: ?string;
-  _generatedSchema: ?GraphQLSchema;
-  _explicitSchemaListener: ?SchemaListener;
+  _currentPluginName: string | null | undefined;
+  _generatedSchema: GraphQLSchema | null | undefined;
+  _explicitSchemaListener: SchemaListener | null | undefined;
   _busy: boolean;
   _watching: boolean;
 
@@ -230,7 +236,7 @@ class SchemaBuilder extends EventEmitter {
     };
   }
 
-  _setPluginName(name: ?string) {
+  _setPluginName(name: string | null | undefined) {
     this._currentPluginName = name;
   }
 
@@ -242,9 +248,9 @@ class SchemaBuilder extends EventEmitter {
    *
    * The function must either return a replacement object for `obj` or `obj` itself
    */
-  hook<T: *>(
+  hook<T extends any>(
     hookName: string,
-    fn: Hook<T, *, *>,
+    fn: Hook<T, any, any>,
     provides?: Array<string>,
     before?: Array<string>,
     after?: Array<string>
@@ -356,8 +362,8 @@ class SchemaBuilder extends EventEmitter {
     }
   }
 
-  applyHooks<T: *, Context>(
-    build: { ...Build },
+  applyHooks<T extends any, Context>(
+    build: Build,
     hookName: string,
     input: T,
     context: Context,
@@ -370,13 +376,13 @@ class SchemaBuilder extends EventEmitter {
     try {
       debug(`${INDENT.repeat(this.depth)}[${hookName}${debugStr}]: Running...`);
 
-      const hooks: Array<Hook<T, *, *>> = this.hooks[hookName];
+      const hooks: Array<Hook<T, any, any>> = this.hooks[hookName];
       if (!hooks) {
         throw new Error(`Sorry, '${hookName}' is not a registered hook`);
       }
 
       let newObj = input;
-      for (const hook: Hook<T, *, *> of hooks) {
+      for (const hook: Hook<T, any, any> of hooks) {
         this.depth++;
         try {
           const hookDisplayName = hook.displayName || hook.name || "anonymous";
@@ -405,6 +411,7 @@ class SchemaBuilder extends EventEmitter {
               console.warn(
                 `Build hook '${hookDisplayName}' returned a new object; please use 'return build.extend(build, {...})' instead.`
               );
+
               // Copy everything from newObj back to oldObj
               Object.assign(oldObj, newObj);
               // Go back to the old objectect
@@ -447,7 +454,7 @@ class SchemaBuilder extends EventEmitter {
     this.unwatchers.push(unlisten);
   }
 
-  createBuild(): { ...Build } {
+  createBuild(): Build {
     const initialBuild = makeNewBuild(this);
     // Inflection needs to come first, in case 'build' hooks depend on it
     initialBuild.inflection = this.applyHooks(
@@ -458,14 +465,17 @@ class SchemaBuilder extends EventEmitter {
         scope: {},
       }
     );
+
     const build = this.applyHooks(initialBuild, "build", initialBuild, {
       scope: {},
     });
+
     // Bind all functions so they can be dereferenced
     bindAll(
       build,
       Object.keys(build).filter(key => typeof build[key] === "function")
     );
+
     Object.freeze(build);
     this.applyHooks(build, "init", {}, { scope: {} });
     return build;
@@ -479,11 +489,13 @@ class SchemaBuilder extends EventEmitter {
         {
           directives: [...build.graphql.specifiedDirectives],
         },
+
         {
           __origin: `GraphQL built-in`,
           isSchema: true,
         }
       );
+
       this._generatedSchema = this.applyHooks(
         build,
         "finalize",
@@ -523,6 +535,7 @@ class SchemaBuilder extends EventEmitter {
           console.error(
             "⚠️⚠️⚠️ An error occured when building the schema on watch:"
           );
+
           // eslint-disable-next-line no-console
           console.error(e);
         }
diff --git a/packages/graphile-build/src/callbackToAsyncIterator.js b/packages/graphile-build/src/callbackToAsyncIterator.ts
similarity index 83%
rename from packages/graphile-build/src/callbackToAsyncIterator.js
rename to packages/graphile-build/src/callbackToAsyncIterator.ts
index d51a21945..2bbbfdd29 100644
--- a/packages/graphile-build/src/callbackToAsyncIterator.js
+++ b/packages/graphile-build/src/callbackToAsyncIterator.ts
@@ -1,4 +1,3 @@
-// @flow
 /* eslint-disable flowtype/no-weak-types */
 // Turn a callback-based listener into an async iterator
 // From https://raw.githubusercontent.com/withspectrum/callback-to-async-iterator/master/src/index.js
@@ -11,14 +10,16 @@ const defaultOnError = (err: Error) => {
 };
 
 export default function callbackToAsyncIterator<
-  CallbackInput: any,
-  ReturnVal: any
+  CallbackInput extends any,
+  ReturnVal extends any
 >(
-  listener: ((arg: CallbackInput) => any) => ?ReturnVal | Promise<?ReturnVal>,
+  listener: (
+    a: (arg: CallbackInput) => any
+  ) => (ReturnVal | null | undefined) | Promise<ReturnVal | null | undefined>,
   options?: {
-    onError?: (err: Error) => void,
-    onClose?: (arg?: ?ReturnVal) => void,
-    buffering?: boolean,
+    onError?: (err: Error) => undefined;
+    onClose?: (arg: ReturnVal | null | undefined) => undefined;
+    buffering?: boolean;
   } = {}
 ) {
   const { onError = defaultOnError, buffering = true, onClose } = options;
@@ -66,10 +67,10 @@ export default function callbackToAsyncIterator<
       });
 
     return {
-      next(): Promise<{ value?: CallbackInput, done: boolean }> {
+      next(): Promise<{ value?: CallbackInput; done: boolean }> {
         return listening ? pullValue() : this.return();
       },
-      return(): Promise<{ value: typeof undefined, done: boolean }> {
+      return(): Promise<{ value: typeof undefined; done: boolean }> {
         emptyQueue();
         return Promise.resolve({ value: undefined, done: true });
       },
diff --git a/packages/graphile-build/src/extend.js b/packages/graphile-build/src/extend.ts
similarity index 91%
rename from packages/graphile-build/src/extend.js
rename to packages/graphile-build/src/extend.ts
index 48306ebde..3a2e254c8 100644
--- a/packages/graphile-build/src/extend.js
+++ b/packages/graphile-build/src/extend.ts
@@ -1,4 +1,3 @@
-// @flow
 import chalk from "chalk";
 
 const INDENT = "  ";
@@ -10,7 +9,7 @@ export function indent(text: string) {
   );
 }
 
-export default function extend<Obj1: *, Obj2: *>(
+export default function extend<Obj1 extends any, Obj2 extends any>(
   base: Obj1,
   extra: Obj2,
   hint?: string
@@ -25,7 +24,7 @@ export default function extend<Obj1: *, Obj2: *>(
     const hintB = extraHints[key] || hint;
     if (key in base && base[key] !== newValue) {
       // $FlowFixMe
-      const hintA: ?string = hints[key];
+      const hintA: string | null | undefined = hints[key];
       const firstEntityDetails = !hintA
         ? "We don't have any information about the first entity."
         : `The first entity was:\n\n${indent(chalk.magenta(hintA))}`;
diff --git a/packages/graphile-build/src/index.d.ts b/packages/graphile-build/src/index.d.ts
index 56c739285..73dbfcdf5 100644
--- a/packages/graphile-build/src/index.d.ts
+++ b/packages/graphile-build/src/index.d.ts
@@ -3,9 +3,9 @@ import { ResolveTree } from "graphql-parse-resolve-info";
 
 type CaseChangeFunction = (str: string) => string;
 export const constantCaseAll: CaseChangeFunction;
-export const formatInsideUnderscores: ((
+export const formatInsideUnderscores: (
   fn: CaseChangeFunction
-) => CaseChangeFunction);
+) => CaseChangeFunction;
 export const upperFirst: CaseChangeFunction;
 export const camelCase: CaseChangeFunction;
 export const constantCase: CaseChangeFunction;
@@ -35,12 +35,7 @@ export {
   Context,
   Hook,
 } from "./SchemaBuilder";
-export {
-  LiveSource,
-  LiveProvider,
-  LiveMonitor,
-  LiveCoordinator,
-} from "./Live";
+export { LiveSource, LiveProvider, LiveMonitor, LiveCoordinator } from "./Live";
 export { SchemaBuilder };
 
 export const getBuilder: (
diff --git a/packages/graphile-build/src/index.js b/packages/graphile-build/src/index.ts
similarity index 92%
rename from packages/graphile-build/src/index.js
rename to packages/graphile-build/src/index.ts
index 5822caa86..dad4b8b7d 100644
--- a/packages/graphile-build/src/index.js
+++ b/packages/graphile-build/src/index.ts
@@ -1,5 +1,3 @@
-// @flow
-
 import util from "util";
 import SchemaBuilder from "./SchemaBuilder";
 import {
@@ -14,9 +12,9 @@ import {
   AddQueriesToSubscriptionsPlugin,
 } from "./plugins";
 import resolveNode from "./resolveNode";
-import type { GraphQLSchema } from "graphql";
+import { GraphQLSchema } from "graphql";
 
-import type { Plugin, Options } from "./SchemaBuilder";
+import { Plugin, Options } from "./SchemaBuilder";
 
 export {
   constantCaseAll,
@@ -29,9 +27,9 @@ export {
   singularize,
 } from "./utils";
 
-export type { SchemaBuilder };
+export { SchemaBuilder };
 
-export type {
+export {
   Plugin,
   Options,
   Build,
@@ -41,7 +39,7 @@ export type {
   Hook,
   WatchUnwatch,
   SchemaListener,
-} from "./SchemaBuilder";
+};
 
 export { LiveSource, LiveProvider, LiveMonitor, LiveCoordinator } from "./Live";
 
diff --git a/packages/graphile-build/src/makeNewBuild.js b/packages/graphile-build/src/makeNewBuild.ts
similarity index 96%
rename from packages/graphile-build/src/makeNewBuild.js
rename to packages/graphile-build/src/makeNewBuild.ts
index 5eed83570..5e5c4db38 100644
--- a/packages/graphile-build/src/makeNewBuild.js
+++ b/packages/graphile-build/src/makeNewBuild.ts
@@ -1,7 +1,5 @@
-// @flow
-
 import * as graphql from "graphql";
-import type {
+import {
   GraphQLNamedType,
   GraphQLInputField,
   GraphQLFieldResolver,
@@ -13,7 +11,7 @@ import {
   getAliasFromResolveInfo as rawGetAliasFromResolveInfo,
 } from "graphql-parse-resolve-info";
 import debugFactory from "debug";
-import type { ResolveTree } from "graphql-parse-resolve-info";
+import { ResolveTree } from "graphql-parse-resolve-info";
 import pluralize from "pluralize";
 import LRU from "@graphile/lru";
 import semver from "semver";
@@ -22,7 +20,7 @@ import swallowError from "./swallowError";
 import resolveNode from "./resolveNode";
 import { LiveCoordinator } from "./Live";
 
-import type SchemaBuilder, {
+import SchemaBuilder, {
   Build,
   Context,
   Scope,
@@ -107,43 +105,44 @@ function getSafeAliasFromResolveInfo(resolveInfo) {
 }
 
 type MetaData = {
-  [string]: Array<mixed>,
+  [a: string]: Array<unknown>;
 };
+
 type DataGeneratorFunction = (
   parsedResolveInfoFragment: ResolveTree,
   ReturnType: GraphQLType,
-  ...args: Array<mixed>
+  ...args: Array<unknown>
 ) => Array<MetaData>;
 
 type FieldSpecIsh = {
-  type?: GraphQLType,
-  args?: {},
-  resolve?: GraphQLFieldResolver<*, *>,
-  deprecationReason?: string,
-  description?: ?string,
+  type?: GraphQLType;
+  args?: {};
+  resolve?: GraphQLFieldResolver<any, any>;
+  deprecationReason?: string;
+  description?: string | null | undefined;
 };
 
 type ContextAndGenerators =
   | Context
   | {
-      addDataGenerator: DataGeneratorFunction => void,
-      addArgDataGenerator: DataGeneratorFunction => void,
+      addDataGenerator: (a: DataGeneratorFunction) => undefined;
+      addArgDataGenerator: (a: DataGeneratorFunction) => undefined;
       getDataFromParsedResolveInfoFragment: (
         parsedResolveInfoFragment: ResolveTree,
         Type: GraphQLType
-      ) => DataForType,
+      ) => DataForType;
     };
 
 export type FieldWithHooksFunction = (
   fieldName: string,
-  spec: FieldSpecIsh | (ContextAndGenerators => FieldSpecIsh),
-  fieldScope?: {}
+  spec: FieldSpecIsh | ((a: ContextAndGenerators) => FieldSpecIsh),
+  fieldScope: {}
 ) => {};
 
 export type InputFieldWithHooksFunction = (
   fieldName: string,
   spec: GraphQLInputField,
-  fieldScope?: {}
+  fieldScope: {}
 ) => GraphQLInputField;
 
 function getNameFromType(Type: GraphQLNamedType | GraphQLSchema) {
@@ -172,7 +171,9 @@ const mergeData = (
   ReturnType,
   arg
 ) => {
-  const results: ?Array<MetaData> = ensureArray(gen(arg, ReturnType, data));
+  const results: Array<MetaData> | null | undefined = ensureArray(
+    gen(arg, ReturnType, data)
+  );
   if (!results) {
     return;
   }
@@ -186,8 +187,8 @@ const mergeData = (
     for (let i = 0, l = keys.length; i < l; i++) {
       const k = keys[i];
       data[k] = data[k] || [];
-      const value: mixed = result[k];
-      const newData: ?Array<mixed> = ensureArray(value);
+      const value: unknown = result[k];
+      const newData: Array<unknown> | null | undefined = ensureArray(value);
       if (newData) {
         data[k].push(...newData);
       }
@@ -202,9 +203,10 @@ const knownTypes = [
   GraphQLEnumType,
   GraphQLUnionType,
 ];
+
 const knownTypeNames = knownTypes.map(k => k.name);
 
-function ensureArray<T>(val: void | Array<T> | T): void | Array<T> {
+function ensureArray<T>(val: undefined | Array<T> | T): undefined | Array<T> {
   if (val == null) {
     return;
   } else if (Array.isArray(val)) {
@@ -227,7 +229,7 @@ if (["development", "test"].indexOf(process.env.NODE_ENV) >= 0) {
   };
 }
 
-export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
+export default function makeNewBuild(builder: SchemaBuilder): Build {
   const allTypes = {
     Int: graphql.GraphQLInt,
     Float: graphql.GraphQLFloat,
@@ -235,6 +237,7 @@ export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
     Boolean: graphql.GraphQLBoolean,
     ID: graphql.GraphQLID,
   };
+
   const allTypesSources = {
     Int: "GraphQL Built-in",
     Float: "GraphQL Built-in",
@@ -265,6 +268,7 @@ export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
       graphql: require("graphql/package.json").version,
       "graphile-build": version,
     },
+
     hasVersion(
       packageName: string,
       range: string,
@@ -284,7 +288,10 @@ export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
       const alias = getSafeAliasFromResolveInfo(resolveInfo);
       return data[alias];
     },
-    addType(type: GraphQLNamedType, origin?: ?string): void {
+    addType(
+      type: GraphQLNamedType,
+      origin?: string | null | undefined
+    ): undefined {
       if (!type.name) {
         throw new Error(
           `addType must only be called with named types, try using require('graphql').getNamedType`
@@ -326,12 +333,15 @@ export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
       return allTypes[typeName];
     },
     extend,
-    newWithHooks<T: GraphQLNamedType | GraphQLSchema, ConfigType: *>(
+    newWithHooks<
+      T extends GraphQLNamedType | GraphQLSchema,
+      ConfigType extends any
+    >(
       Type: Class<T>,
       spec: ConfigType,
       inScope: Scope,
       performNonEmptyFieldsCheck = false
-    ): ?T {
+    ): T | null | undefined {
       const scope = inScope || {};
       if (!inScope) {
         // eslint-disable-next-line no-console
@@ -404,14 +414,17 @@ export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
               parsedResolveInfoFragment,
               ReturnType
             );
+
             const results = [];
             const StrippedType: GraphQLNamedType = getNamedType(ReturnType);
             const fieldDataGeneratorsByFieldName = fieldDataGeneratorsByFieldNameByType.get(
               StrippedType
             );
+
             const argDataGeneratorsForSelfByFieldName = fieldArgDataGeneratorsByFieldNameByType.get(
               Self
             );
+
             if (argDataGeneratorsForSelfByFieldName) {
               const argDataGenerators =
                 argDataGeneratorsForSelfByFieldName[fieldName];
@@ -453,6 +466,7 @@ export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
                     const local = ensureArray(
                       gen(field, typeFields[field.name].type, ...rest)
                     );
+
                     if (local) {
                       results.push(...local);
                     }
@@ -473,6 +487,7 @@ export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
           type: "GraphQLObjectType",
           scope,
         };
+
         newSpec = builder.applyHooks(
           this,
           "GraphQLObjectType",
@@ -482,6 +497,7 @@ export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
             addDataGeneratorForField,
             recurseDataGeneratorsForField,
           },
+
           `|${newSpec.name}`
         );
 
@@ -494,6 +510,7 @@ export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
               Self,
               GraphQLObjectType: rawSpec,
             };
+
             let rawInterfaces = rawSpec.interfaces || [];
             if (typeof rawInterfaces === "function") {
               rawInterfaces = rawInterfaces(interfacesContext);
@@ -579,6 +596,7 @@ export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
                           fieldName,
                           getNameFromType(Self)
                         );
+
                         throw e;
                       }
                     }
@@ -592,6 +610,7 @@ export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
                     const fieldDataGeneratorsByFieldName = fieldDataGeneratorsByFieldNameByType.get(
                       Type
                     );
+
                     if (
                       fieldDataGeneratorsByFieldName &&
                       isCompositeType(Type) &&
@@ -623,14 +642,17 @@ export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
                       {
                         fieldName,
                       },
+
                       `Within context for GraphQLObjectType '${rawSpec.name}'`
                     ),
+
                     fieldScope,
                     `Extending scope for field '${fieldName}' within context for GraphQLObjectType '${
                       rawSpec.name
                     }'`
                   ),
                 };
+
                 if (typeof newSpec === "function") {
                   newSpec = newSpec(context);
                 }
@@ -641,6 +663,7 @@ export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
                   context,
                   `|${getNameFromType(Self)}.fields.${fieldName}`
                 );
+
                 newSpec.args = newSpec.args || {};
                 newSpec = {
                   ...newSpec,
@@ -653,14 +676,17 @@ export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
                       field: newSpec,
                       returnType: newSpec.type,
                     },
+
                     `|${getNameFromType(Self)}.fields.${fieldName}`
                   ),
                 };
+
                 const finalSpec = newSpec;
                 processedFields.push(finalSpec);
                 return finalSpec;
-              }: FieldWithHooksFunction),
+              }) as FieldWithHooksFunction,
             };
+
             let rawFields = rawSpec.fields || {};
             if (typeof rawFields === "function") {
               rawFields = rawFields(fieldsContext);
@@ -675,9 +701,11 @@ export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
                   rawSpec.name
                 }'. ${inScope.__origin || ""}`
               ),
+
               fieldsContext,
               `|${rawSpec.name}`
             );
+
             // Finally, check through all the fields that they've all been processed; any that have not we should do so now.
             for (const fieldName in fieldsSpec) {
               const fieldSpec = fieldsSpec[fieldName];
@@ -700,6 +728,7 @@ export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
           type: "GraphQLInputObjectType",
           scope,
         };
+
         newSpec = builder.applyHooks(
           this,
           "GraphQLInputObjectType",
@@ -707,6 +736,7 @@ export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
           commonContext,
           `|${newSpec.name}`
         );
+
         newSpec.fields = newSpec.fields || {};
 
         const rawSpec = newSpec;
@@ -733,16 +763,19 @@ export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
                       {
                         fieldName,
                       },
+
                       `Within context for GraphQLInputObjectType '${
                         rawSpec.name
                       }'`
                     ),
+
                     fieldScope,
                     `Extending scope for field '${fieldName}' within context for GraphQLInputObjectType '${
                       rawSpec.name
                     }'`
                   ),
                 };
+
                 let newSpec = spec;
                 if (typeof newSpec === "function") {
                   newSpec = newSpec(context);
@@ -754,11 +787,13 @@ export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
                   context,
                   `|${getNameFromType(Self)}.fields.${fieldName}`
                 );
+
                 const finalSpec = newSpec;
                 processedFields.push(finalSpec);
                 return finalSpec;
-              }: InputFieldWithHooksFunction),
+              }) as InputFieldWithHooksFunction,
             };
+
             let rawFields = rawSpec.fields;
             if (typeof rawFields === "function") {
               rawFields = rawFields(fieldsContext);
@@ -773,9 +808,11 @@ export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
                   rawSpec.name
                 }'. ${inScope.__origin || ""}`
               ),
+
               fieldsContext,
               `|${getNameFromType(Self)}`
             );
+
             // Finally, check through all the fields that they've all been processed; any that have not we should do so now.
             for (const fieldName in fieldsSpec) {
               const fieldSpec = fieldsSpec[fieldName];
@@ -798,6 +835,7 @@ export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
           type: "GraphQLEnumType",
           scope,
         };
+
         newSpec = builder.applyHooks(
           this,
           "GraphQLEnumType",
@@ -813,6 +851,7 @@ export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
           commonContext,
           `|${newSpec.name}`
         );
+
         const values = newSpec.values;
         newSpec.values = Object.keys(values).reduce((memo, valueKey) => {
           const value = values[valueKey];
@@ -823,6 +862,7 @@ export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
             commonContext,
             `|${newSpec.name}|${valueKey}`
           );
+
           memo[valueKey] = newValue;
           return memo;
         }, {});
@@ -831,6 +871,7 @@ export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
           type: "GraphQLUnionType",
           scope,
         };
+
         newSpec = builder.applyHooks(
           this,
           "GraphQLUnionType",
@@ -848,6 +889,7 @@ export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
               Self,
               GraphQLUnionType: rawSpec,
             };
+
             let rawTypes = rawSpec.types || [];
             if (typeof rawTypes === "function") {
               rawTypes = rawTypes(typesContext);
@@ -894,6 +936,7 @@ export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
           const isProbablyAnEmptyObjectError = !!e.message.match(
             /function which returns such an object/
           );
+
           if (!isProbablyAnEmptyObjectError) {
             this.swallowError(e);
           }
@@ -917,10 +960,12 @@ export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
         Self,
         fieldDataGeneratorsByFieldName
       );
+
       fieldArgDataGeneratorsByFieldNameByType.set(
         Self,
         fieldArgDataGeneratorsByFieldName
       );
+
       return Self;
     },
     fieldDataGeneratorsByType: fieldDataGeneratorsByFieldNameByType, // @deprecated
@@ -995,6 +1040,7 @@ export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
         return resultingName;
       },
     },
+
     swallowError,
     // resolveNode: EXPERIMENTAL, API might change!
     resolveNode,
@@ -1002,6 +1048,7 @@ export default function makeNewBuild(builder: SchemaBuilder): { ...Build } {
       currentHookName: null,
       currentHookEvent: null,
     },
+
     liveCoordinator: new LiveCoordinator(),
     scopeByType: new Map(),
   };
diff --git a/packages/graphile-build/src/plugins/AddQueriesToSubscriptionsPlugin.js b/packages/graphile-build/src/plugins/AddQueriesToSubscriptionsPlugin.ts
similarity index 95%
rename from packages/graphile-build/src/plugins/AddQueriesToSubscriptionsPlugin.js
rename to packages/graphile-build/src/plugins/AddQueriesToSubscriptionsPlugin.ts
index 4a9d161b1..caa8b5455 100644
--- a/packages/graphile-build/src/plugins/AddQueriesToSubscriptionsPlugin.js
+++ b/packages/graphile-build/src/plugins/AddQueriesToSubscriptionsPlugin.ts
@@ -1,6 +1,5 @@
-// @flow
-import type { Plugin } from "../SchemaBuilder";
-import type { GraphQLObjectType } from "graphql";
+import { Plugin } from "../SchemaBuilder";
+import { GraphQLObjectType } from "graphql";
 
 const AddQueriesToSubscriptionsPlugin: Plugin = function(
   builder,
@@ -24,6 +23,7 @@ const AddQueriesToSubscriptionsPlugin: Plugin = function(
       const Query: GraphQLObjectType = getTypeByName(
         inflection.builtin("Query")
       );
+
       const queryFields = Query.getFields();
       const subscriptionFields = Object.keys(queryFields).reduce(
         (memo, queryFieldName) => {
@@ -41,6 +41,7 @@ const AddQueriesToSubscriptionsPlugin: Plugin = function(
                   type,
                   defaultValue,
                 };
+
                 return newArgs;
               }, {}),
               ...(oldResolve
@@ -66,15 +67,18 @@ const AddQueriesToSubscriptionsPlugin: Plugin = function(
                 ? queryField.deprecationReason
                 : undefined,
             },
+
             {
               isLiveField: true,
               originalField: queryField,
             }
           );
+
           return memo;
         },
         {}
       );
+
       return extend(fields, subscriptionFields);
     },
     ["AddQueriesToSubscriptions"]
diff --git a/packages/graphile-build/src/plugins/ClientMutationIdDescriptionPlugin.js b/packages/graphile-build/src/plugins/ClientMutationIdDescriptionPlugin.ts
similarity index 93%
rename from packages/graphile-build/src/plugins/ClientMutationIdDescriptionPlugin.js
rename to packages/graphile-build/src/plugins/ClientMutationIdDescriptionPlugin.ts
index 143e968d1..7b6341fb6 100644
--- a/packages/graphile-build/src/plugins/ClientMutationIdDescriptionPlugin.js
+++ b/packages/graphile-build/src/plugins/ClientMutationIdDescriptionPlugin.ts
@@ -1,7 +1,6 @@
-// @flow
-import type SchemaBuilder, { Plugin } from "../SchemaBuilder";
+import SchemaBuilder, { Plugin } from "../SchemaBuilder";
 
-export default (function ClientMutationIdDescriptionPlugin(
+export default function ClientMutationIdDescriptionPlugin(
   builder: SchemaBuilder
 ) {
   builder.hook(
@@ -25,6 +24,7 @@ export default (function ClientMutationIdDescriptionPlugin(
           description:
             "An arbitrary string value with no semantic meaning. Will be included in the payload verbatim. May be used to track mutations by the client.",
         },
+
         `Tweaking '${fieldName}' field in '${Self.name}'`
       );
     },
@@ -52,6 +52,7 @@ export default (function ClientMutationIdDescriptionPlugin(
           description:
             "The exact same `clientMutationId` that was provided in the mutation input, unchanged and unused. May be used by a client to track mutations.",
         },
+
         `Tweaking '${fieldName}' field in '${Self.name}'`
       );
     },
@@ -77,6 +78,7 @@ export default (function ClientMutationIdDescriptionPlugin(
             description:
               "The exclusive input argument for this mutation. An object type, make sure to see documentation for this object’s fields.",
           },
+
           `Adding a description to input arg for field '${fieldName}' field in '${
             Self.name
           }'`
@@ -85,4 +87,4 @@ export default (function ClientMutationIdDescriptionPlugin(
     },
     ["ClientMutationIdDescription"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build/src/plugins/MutationPayloadQueryPlugin.js b/packages/graphile-build/src/plugins/MutationPayloadQueryPlugin.ts
similarity index 71%
rename from packages/graphile-build/src/plugins/MutationPayloadQueryPlugin.js
rename to packages/graphile-build/src/plugins/MutationPayloadQueryPlugin.ts
index 32bda96b0..35af86391 100644
--- a/packages/graphile-build/src/plugins/MutationPayloadQueryPlugin.js
+++ b/packages/graphile-build/src/plugins/MutationPayloadQueryPlugin.ts
@@ -1,15 +1,10 @@
-// @flow
-import type { Plugin, Build } from "../SchemaBuilder";
-import type { BuildExtensionQuery } from "./QueryPlugin";
+import { Plugin, Build } from "../SchemaBuilder";
+import { BuildExtensionQuery } from "./QueryPlugin";
 
-export default (function MutationPayloadQueryPlugin(builder) {
+export default function MutationPayloadQueryPlugin(builder) {
   builder.hook(
     "GraphQLObjectType:fields",
-    (
-      fields: {},
-      build: {| ...Build, ...BuildExtensionQuery |},
-      context
-    ): {} => {
+    (fields: {}, build: Build & BuildExtensionQuery, context): {} => {
       const { $$isQuery, extend, getTypeByName, inflection } = build;
       const {
         scope: { isMutationPayload },
@@ -31,9 +26,10 @@ export default (function MutationPayloadQueryPlugin(builder) {
             },
           },
         },
+
         `Adding 'query' field to mutation payload ${Self.name}`
       );
     },
     ["MutationPayloadQuery"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build/src/plugins/MutationPlugin.js b/packages/graphile-build/src/plugins/MutationPlugin.ts
similarity index 89%
rename from packages/graphile-build/src/plugins/MutationPlugin.js
rename to packages/graphile-build/src/plugins/MutationPlugin.ts
index aa3e53d2f..e16c3d07b 100644
--- a/packages/graphile-build/src/plugins/MutationPlugin.js
+++ b/packages/graphile-build/src/plugins/MutationPlugin.ts
@@ -1,5 +1,4 @@
-// @flow
-import type { Plugin } from "../SchemaBuilder";
+import { Plugin } from "../SchemaBuilder";
 
 function isValidMutation(Mutation) {
   try {
@@ -15,7 +14,7 @@ function isValidMutation(Mutation) {
   return true;
 }
 
-export default (async function MutationPlugin(builder) {
+export default async function MutationPlugin(builder) {
   builder.hook(
     "GraphQLSchema",
     (schema: {}, build) => {
@@ -32,18 +31,22 @@ export default (async function MutationPlugin(builder) {
           description:
             "The root mutation type which contains root level fields which mutate data.",
         },
+
         {
           __origin: `graphile-build built-in (root mutation type)`,
           isRootMutation: true,
         },
+
         true
       );
+
       if (isValidMutation(Mutation)) {
         return extend(
           schema,
           {
             mutation: Mutation,
           },
+
           "Adding mutation type to schema"
         );
       } else {
@@ -54,4 +57,4 @@ export default (async function MutationPlugin(builder) {
     [],
     ["Query"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build/src/plugins/NodePlugin.js b/packages/graphile-build/src/plugins/NodePlugin.ts
similarity index 85%
rename from packages/graphile-build/src/plugins/NodePlugin.js
rename to packages/graphile-build/src/plugins/NodePlugin.ts
index 264371a78..a3ebbd664 100644
--- a/packages/graphile-build/src/plugins/NodePlugin.js
+++ b/packages/graphile-build/src/plugins/NodePlugin.ts
@@ -1,53 +1,52 @@
-// @flow
-import type {
+import {
   Plugin,
   Build,
   DataForType,
   Context,
   ContextGraphQLObjectTypeFields,
 } from "../SchemaBuilder";
-import type { ResolveTree } from "graphql-parse-resolve-info";
-import type {
-  GraphQLType,
-  GraphQLInterfaceType,
-  GraphQLResolveInfo,
-} from "graphql";
-import type { BuildExtensionQuery } from "./QueryPlugin";
+import { ResolveTree } from "graphql-parse-resolve-info";
+import { GraphQLType, GraphQLInterfaceType, GraphQLResolveInfo } from "graphql";
+import { BuildExtensionQuery } from "./QueryPlugin";
 
 const base64 = str => Buffer.from(String(str)).toString("base64");
 const base64Decode = str => Buffer.from(String(str), "base64").toString("utf8");
 
 export type NodeFetcher = (
-  data: mixed,
-  identifiers: Array<mixed>,
-  context: mixed,
+  data: unknown,
+  identifiers: Array<unknown>,
+  context: unknown,
   parsedResolveInfoFragment: ResolveTree,
   type: GraphQLType,
   resolveData: DataForType,
   resolveInfo: GraphQLResolveInfo
 ) => {};
 
-export type BuildExtensionNode = {|
-  nodeIdFieldName: string,
-  $$nodeType: Symbol,
-  nodeFetcherByTypeName: { [string]: NodeFetcher },
-  getNodeIdForTypeAndIdentifiers(
+export type BuildExtensionNode = {
+  nodeIdFieldName: string;
+  $$nodeType: Symbol;
+  nodeFetcherByTypeName: { [a: string]: NodeFetcher };
+  getNodeIdForTypeAndIdentifiers: (
     Type: GraphQLType,
-    ...identifiers: Array<mixed>
-  ): string,
-  getTypeAndIdentifiersFromNodeId(
+    ...identifiers: Array<unknown>
+  ) => string;
+  getTypeAndIdentifiersFromNodeId: (
     nodeId: string
-  ): {
-    Type: GraphQLType,
-    identifiers: Array<mixed>,
-  },
-  addNodeFetcherForTypeName(typeName: string, fetcher: NodeFetcher): void,
-  getNodeAlias(typeName: string): string,
-  getNodeType(alias: string): GraphQLType,
-  setNodeAlias(typeName: string, alias: string): void,
-|};
+  ) => {
+    Type: GraphQLType;
+    identifiers: Array<unknown>;
+  };
+
+  addNodeFetcherForTypeName: (
+    typeName: string,
+    fetcher: NodeFetcher
+  ) => undefined;
+  getNodeAlias: (typeName: string) => string;
+  getNodeType: (alias: string) => GraphQLType;
+  setNodeAlias: (typeName: string, alias: string) => undefined;
+};
 
-export default (function NodePlugin(
+export default function NodePlugin(
   builder,
   { nodeIdFieldName: inNodeIdFieldName }
 ) {
@@ -109,6 +108,7 @@ export default (function NodePlugin(
             nodeTypeNameByAlias[alias] = typeName;
           },
         },
+
         `Adding 'Node' interface support to the Build`
       );
     },
@@ -119,7 +119,7 @@ export default (function NodePlugin(
     "init",
     function defineNodeInterfaceType(
       _: {},
-      build: {| ...Build, ...BuildExtensionQuery, ...BuildExtensionNode |}
+      build: Build & BuildExtensionQuery & BuildExtensionNode
     ) {
       const {
         $$isQuery,
@@ -132,6 +132,7 @@ export default (function NodePlugin(
           GraphQLInterfaceType,
           getNullableType,
         },
+
         inflection,
       } = build;
       let Query;
@@ -156,10 +157,12 @@ export default (function NodePlugin(
             },
           },
         },
+
         {
           __origin: `graphile-build built-in (NodePlugin); you can omit this plugin if you like, but you'll lose compatibility with Relay`,
         }
       );
+
       return _;
     },
     ["Node"]
@@ -193,8 +196,8 @@ export default (function NodePlugin(
     "GraphQLObjectType:fields",
     (
       fields: {},
-      build: {| ...Build, ...BuildExtensionQuery, ...BuildExtensionNode |},
-      context: {| ...Context, ...ContextGraphQLObjectTypeFields |}
+      build: Build & BuildExtensionQuery & BuildExtensionNode,
+      context: Context & ContextGraphQLObjectTypeFields
     ) => {
       const {
         scope: { isRootQuery },
@@ -221,6 +224,7 @@ export default (function NodePlugin(
               return "query";
             },
           },
+
           node: fieldWithHooks(
             "node",
             ({ getDataFromParsedResolveInfoFragment }) => ({
@@ -232,6 +236,7 @@ export default (function NodePlugin(
                   type: new GraphQLNonNull(GraphQLID),
                 },
               },
+
               resolve(data, args, context, resolveInfo) {
                 const nodeId = args[nodeIdFieldName];
                 return resolveNode(
@@ -244,14 +249,16 @@ export default (function NodePlugin(
                 );
               },
             }),
+
             {
               isRootNodeField: true,
             }
           ),
         },
+
         `Adding Relay Global Object Identification support to the root Query via 'node' and '${nodeIdFieldName}' fields`
       );
     },
     ["Node"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build/src/plugins/QueryPlugin.js b/packages/graphile-build/src/plugins/QueryPlugin.ts
similarity index 89%
rename from packages/graphile-build/src/plugins/QueryPlugin.js
rename to packages/graphile-build/src/plugins/QueryPlugin.ts
index 0c9d46756..6055f7c15 100644
--- a/packages/graphile-build/src/plugins/QueryPlugin.js
+++ b/packages/graphile-build/src/plugins/QueryPlugin.ts
@@ -1,11 +1,10 @@
-// @flow
-import type { Plugin, Build } from "../SchemaBuilder";
+import { Plugin, Build } from "../SchemaBuilder";
 
-export type BuildExtensionQuery = {|
-  $$isQuery: Symbol,
-|};
+export type BuildExtensionQuery = {
+  $$isQuery: Symbol;
+};
 
-export default (async function QueryPlugin(builder) {
+export default async function QueryPlugin(builder) {
   builder.hook(
     "build",
     (build: Build): Build & BuildExtensionQuery =>
@@ -14,10 +13,13 @@ export default (async function QueryPlugin(builder) {
         {
           $$isQuery: Symbol("isQuery"),
         },
+
         `Extending Build`
       ),
+
     ["Query"]
   );
+
   builder.hook(
     "GraphQLSchema",
     (schema: {}, build) => {
@@ -47,18 +49,22 @@ export default (async function QueryPlugin(builder) {
             },
           }),
         },
+
         {
           __origin: `graphile-build built-in (root query type)`,
           isRootQuery: true,
         },
+
         true
       );
+
       if (queryType) {
         return extend(
           schema,
           {
             query: queryType,
           },
+
           `Adding 'query' type to Schema`
         );
       } else {
@@ -67,4 +73,4 @@ export default (async function QueryPlugin(builder) {
     },
     ["Query"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build/src/plugins/StandardTypesPlugin.js b/packages/graphile-build/src/plugins/StandardTypesPlugin.ts
similarity index 95%
rename from packages/graphile-build/src/plugins/StandardTypesPlugin.js
rename to packages/graphile-build/src/plugins/StandardTypesPlugin.ts
index de841dc87..832643973 100644
--- a/packages/graphile-build/src/plugins/StandardTypesPlugin.js
+++ b/packages/graphile-build/src/plugins/StandardTypesPlugin.ts
@@ -1,8 +1,7 @@
-// @flow
-import type { Plugin, Build } from "../SchemaBuilder";
+import { Plugin, Build } from "../SchemaBuilder";
 import { Kind } from "graphql/language";
 
-export default (function StandardTypesPlugin(builder) {
+export default function StandardTypesPlugin(builder) {
   // XXX: this should be in an "init" plugin, but PgTypesPlugin requires it in build - fix that, then fix this
   builder.hook(
     "build",
@@ -25,11 +24,13 @@ export default (function StandardTypesPlugin(builder) {
         "Cursor",
         "A location in a connection that can be used for resuming pagination."
       );
+
       build.addType(Cursor, "graphile-build built-in");
       return build;
     },
     ["StandardTypes"]
   );
+
   builder.hook(
     "init",
     (_: {}, build) => {
@@ -62,6 +63,7 @@ export default (function StandardTypesPlugin(builder) {
               },
               { isPageInfoHasNextPageField: true }
             ),
+
             hasPreviousPage: fieldWithHooks(
               "hasPreviousPage",
               ({ addDataGenerator }) => {
@@ -80,13 +82,15 @@ export default (function StandardTypesPlugin(builder) {
             ),
           }),
         },
+
         {
           __origin: `graphile-build built-in`,
           isPageInfo: true,
         }
       );
+
       return _;
     },
     ["StandardTypes", "PageInfo"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build/src/plugins/SubscriptionPlugin.js b/packages/graphile-build/src/plugins/SubscriptionPlugin.ts
similarity index 94%
rename from packages/graphile-build/src/plugins/SubscriptionPlugin.js
rename to packages/graphile-build/src/plugins/SubscriptionPlugin.ts
index 567713aa8..1ebeb936c 100644
--- a/packages/graphile-build/src/plugins/SubscriptionPlugin.js
+++ b/packages/graphile-build/src/plugins/SubscriptionPlugin.ts
@@ -1,5 +1,4 @@
-// @flow
-import type { Plugin } from "../SchemaBuilder";
+import { Plugin } from "../SchemaBuilder";
 
 function isValidSubscription(Subscription) {
   try {
@@ -35,7 +34,7 @@ Live queries can be very expensive, so try and keep them small and focussed.
 Event fields will run their selection set when, and only when, the specified server-side event occurs. \
 This makes them a lot more efficient than Live Queries, but it is still recommended that you keep payloads fairly small.`;
 
-export default (async function SubscriptionPlugin(builder, { live }) {
+export default async function SubscriptionPlugin(builder, { live }) {
   builder.hook(
     "GraphQLSchema",
     (schema: {}, build) => {
@@ -51,18 +50,22 @@ export default (async function SubscriptionPlugin(builder, { live }) {
           name: inflection.builtin("Subscription"),
           description: live ? liveDescription : description,
         },
+
         {
           __origin: `graphile-build built-in (root subscription type)`,
           isRootSubscription: true,
         },
+
         true
       );
+
       if (isValidSubscription(Subscription)) {
         return extend(
           schema,
           {
             subscription: Subscription,
           },
+
           "Adding subscription type to schema"
         );
       } else {
@@ -73,4 +76,4 @@ export default (async function SubscriptionPlugin(builder, { live }) {
     [],
     ["Query"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build/src/plugins/SwallowErrorsPlugin.js b/packages/graphile-build/src/plugins/SwallowErrorsPlugin.ts
similarity index 83%
rename from packages/graphile-build/src/plugins/SwallowErrorsPlugin.js
rename to packages/graphile-build/src/plugins/SwallowErrorsPlugin.ts
index dbc42295a..3837ccc08 100644
--- a/packages/graphile-build/src/plugins/SwallowErrorsPlugin.js
+++ b/packages/graphile-build/src/plugins/SwallowErrorsPlugin.ts
@@ -1,7 +1,6 @@
-// @flow
-import type { Plugin, Build } from "../SchemaBuilder";
+import { Plugin, Build } from "../SchemaBuilder";
 
-export default (function SwallowErrorsPlugin(
+export default function SwallowErrorsPlugin(
   builder,
   { dontSwallowErrors = false }
 ) {
@@ -26,4 +25,4 @@ export default (function SwallowErrorsPlugin(
     },
     ["SwallowErrors"]
   );
-}: Plugin);
+} as Plugin;
diff --git a/packages/graphile-build/src/plugins/index.js b/packages/graphile-build/src/plugins/index.ts
similarity index 98%
rename from packages/graphile-build/src/plugins/index.js
rename to packages/graphile-build/src/plugins/index.ts
index c5a039834..541b59f20 100644
--- a/packages/graphile-build/src/plugins/index.js
+++ b/packages/graphile-build/src/plugins/index.ts
@@ -1,5 +1,3 @@
-// @flow
-
 import ClientMutationIdDescriptionPlugin from "./ClientMutationIdDescriptionPlugin";
 import MutationPayloadQueryPlugin from "./MutationPayloadQueryPlugin";
 import MutationPlugin from "./MutationPlugin";
diff --git a/packages/graphile-build/src/resolveNode.js b/packages/graphile-build/src/resolveNode.ts
similarity index 99%
rename from packages/graphile-build/src/resolveNode.js
rename to packages/graphile-build/src/resolveNode.ts
index 03b50b58a..c82ca99aa 100644
--- a/packages/graphile-build/src/resolveNode.js
+++ b/packages/graphile-build/src/resolveNode.ts
@@ -28,6 +28,7 @@ export default async function resolveNode(
       parsedResolveInfoFragment,
       getNamedType(Type)
     );
+
     const node = await resolver(
       data,
       identifiers,
@@ -37,11 +38,13 @@ export default async function resolveNode(
       resolveData,
       resolveInfo
     );
+
     Object.defineProperty(node, $$nodeType, {
       enumerable: false,
       configurable: false,
       value: Type,
     });
+
     return node;
   } catch (e) {
     return null;
diff --git a/packages/graphile-build/src/swallowError.js b/packages/graphile-build/src/swallowError.ts
similarity index 94%
rename from packages/graphile-build/src/swallowError.js
rename to packages/graphile-build/src/swallowError.ts
index 92035e860..c8c2a5f4d 100644
--- a/packages/graphile-build/src/swallowError.js
+++ b/packages/graphile-build/src/swallowError.ts
@@ -1,9 +1,8 @@
-// @flow
 import debugFactory from "debug";
 
 const debugWarn = debugFactory("graphile-build:warn");
 
-export default function swallowError(e: Error): void {
+export default function swallowError(e: Error): undefined {
   // BE VERY CAREFUL NOT TO THROW!
   // XXX: Improve this
   if (debugWarn.enabled) {
diff --git a/packages/graphile-build/src/utils.js b/packages/graphile-build/src/utils.ts
similarity index 99%
rename from packages/graphile-build/src/utils.js
rename to packages/graphile-build/src/utils.ts
index faa874273..ae90b7390 100644
--- a/packages/graphile-build/src/utils.js
+++ b/packages/graphile-build/src/utils.ts
@@ -1,4 +1,3 @@
-// @flow
 import upperFirstAll from "lodash/upperFirst";
 import camelCaseAll from "lodash/camelCase";
 import plz from "pluralize";