feat: allow providing custom runner per transform file thru CodeshiftConfig

depends on:
- #63

example on how it could be used:
- https://github.com/pipedrive/CodeshiftCommunity/pull/22
    - though note we might refactor into separate PRs, idk,
      preferably would use directly from upstream (you).

fixes a lot of cases for us:

1. we have a postcss codemod that we want to run,
while still utilizing the @codeshift/cli.

though, i don't know if these changes will work
if we're using a remote package, will they?

2. we'll want to do some global pre-processing
on files before running our codemod.

though, there's still no way to provide the codemod
as a __function__ instead of an __import path__ to jscodeshift,
which will force us to do dependency injection
instead of just passing the pre-processed results
as an argument to a function.

this is where the considerations to fork jscodeshift
come into play again:
- #67

Signed-off-by: Kipras Melnikovas <kipras@kipras.org>

Author: kiprasmel

packages/cli/src/main.ts

@@ -6,7 +6,10 @@ import merge from 'lodash/merge';
 // @ts-ignore Run transform(s) on path https://github.com/facebook/jscodeshift/issues/398
 import * as jscodeshift from 'jscodeshift/src/Runner';
 import { isValidConfig } from '@codeshift/validator';
-import { CodeshiftConfig } from '@codeshift/types';
+import {
+  CodeshiftConfig, //
+  DefaultRunner,
+} from '@codeshift/types';
 
 import { Flags } from './types';
 import { InvalidUserInputError } from './errors';
@@ -218,20 +221,95 @@ Make sure the package name ${pkgName} has been spelled correctly and exists befo
     const resolvedTransformPath = path.resolve(transform);
     console.log(chalk.green('Running transform:'), resolvedTransformPath);
 
-    await jscodeshift.run(resolvedTransformPath, paths, {
-      verbose: 0,
-      dry: flags.dry,
-      print: true,
-      babel: true,
-      extensions: flags.extensions,
-      ignorePattern: flags.ignorePattern,
-      cpus: flags.cpus,
-      ignoreConfig: [],
-      runInBand: flags.runInBand,
-      silent: false,
-      parser: flags.parser,
-      stdin: false,
-    });
+    const defaultRunner: DefaultRunner = (
+      jscodeshiftOptionOverrides = {},
+      pathsToModify = paths,
+      /**
+       * ideally you'd be able to pass in either the path,
+       * or the actual transform,
+       * but jscodeshift doesn't allow this (unless we fork?)
+       */
+      transformerPath: string = resolvedTransformPath,
+      /**
+       * i think the jscodeshift.run is synchronous
+       * so the promise is not needed,
+       * but if we want to change it in the future,
+       * making it's return type a promise will help
+       * to avoid breaking changes for consumers who
+       * use the defaultRunner.
+       */
+    ): Promise<void> =>
+      jscodeshift.run(transformerPath, pathsToModify, {
+        verbose: 0,
+        dry: flags.dry,
+        print: true,
+        babel: true,
+        extensions: flags.extensions,
+        ignorePattern: flags.ignorePattern,
+        cpus: flags.cpus,
+        ignoreConfig: [],
+        runInBand: flags.runInBand,
+        silent: false,
+        parser: flags.parser,
+        stdin: false,
+        ...jscodeshiftOptionOverrides,
+      });
+
+    let transformImported: any;
+    try {
+      /**
+       * TODO MAINTAINER -- i am not confident that this will work
+       * if the transform was provided thru an npm package.
+       */
+
+      // eslint-disable-next-line @typescript-eslint/no-var-requires
+      transformImported = require(resolvedTransformPath);
+    } catch (_e) {}
+    console.log({ transformImported });
+
+    const transformHasCustomRunner = (
+      ti: any,
+    ): ti is {
+      /**
+       * ideally, `default` would be the type of the transformer,
+       * which would be identical to the type of the argument to
+       * `CustomTransformerConfig`,
+       *
+       * but unless we put the transformer itself into the config,
+       * we cannot ensure that the type is correct.
+       *
+       */
+      default: unknown; //
+      codeshiftConfig: CodeshiftConfig<unknown>;
+    } => {
+      if (ti && 'codeshiftConfig' in ti) {
+        return 'runner' in transformImported['codeshiftConfig'];
+      }
+      return false;
+    };
+
+    if (transformHasCustomRunner(transformImported)) {
+      await transformImported.codeshiftConfig.runner(paths, {
+        defaultRunner,
+        /**
+         * providing the `transform`, `resolvedTransformPath`, etc. here
+         * is quite useless, because it's file-based,
+         * so in whichever file the config is in,
+         * that default export will be the transform,
+         * and the file's path will be the resolved path.
+         *
+         * ...unless you have a custom runner defined in a separate file,
+         * and want it to be able to access the transform,
+         * esp. if that runner does not take in a path,
+         * but rather the transform function.
+         */
+        transformInsideFileThatSpecifiesCodeshiftConfig:
+          transformImported.default,
+        // resolvedTransformPath
+      });
+    } else {
+      defaultRunner();
+    }
   }
 
   await packageManager.uninstallAll();

packages/types/src/index.ts

@@ -5,3 +5,23 @@ export interface CodeshiftConfig {
   transforms?: Record<string, string>;
   presets?: Record<string, string>;
 }
+
+export type DefaultRunner = (
+  jscodeshiftOptionOverrides?: object,
+  pathsToModify?: string[], //
+  transformerPath?: string,
+) => Promise<void>;
+
+export interface CustomRunnerCtx<Transform = unknown> {
+  transformInsideFileThatSpecifiesCodeshiftConfig: Transform;
+  defaultRunner: DefaultRunner;
+}
+
+export type CustomRunner<Transform = unknown> = (
+  pathsToModify: string[], //
+  options: CustomRunnerCtx<Transform>,
+) => void | Promise<void>;
+
+export interface CodeshiftConfig<Transform = unknown> {
+  runner: CustomRunner<Transform>;
+}