Fix issue where emptyArray was reported unused for lowercase components without children.

Fixes #85.

Author: cristianoc

Changes.md

@@ -1,4 +1,5 @@
 # master
+- Fix issue where `emptyArray` was reported unused for lowercase components without children. (See https://github.com/reason-association/reanalyze/issues/85).
 
 # 2.12.0
 - Support OCaml 4.11 and 4.12.

examples/deadcode/src/EmptyArray.bs.js

@@ -0,0 +1,10 @@
+// @@config({flags : ["-dsource"]});
+
+module Z = {
+  @react.component
+  let make = () => {
+    <br />
+  }
+}
+
+let _ = <Z />

examples/deadcode/src/EmptyArray.res

@@ -401,6 +401,14 @@
   addValueDeclaration +make DynamicallyLoadedComponent.re:2:4 path:+DynamicallyLoadedComponent
   addValueReference DynamicallyLoadedComponent.re:2:32 --> DynamicallyLoadedComponent.re:2:13
   addValueReference DynamicallyLoadedComponent.re:2:19 --> React.re:7:0
+  Scanning EmptyArray.cmt Source:EmptyArray.res
+  addValueDeclaration +make EmptyArray.res:5:6 path:+EmptyArray.Z
+  DeadOptionalArgs.addReferences ReactDOMRe.createDOMElementVariadic called with optional argNames: argNamesMaybe: EmptyArray.res:6:5
+  addValueDeclaration +emptyArray EmptyArray.res:6:5 path:+EmptyArray.Z
+  addDummyReference _none_:1:-1 --> EmptyArray.res:6:5
+  addValueReference EmptyArray.res:6:5 --> ReactDOMRe.re:114:0
+  addValueReference EmptyArray.res:10:9 --> EmptyArray.res:5:6
+  addValueReference EmptyArray.res:10:9 --> React.re:18:0
   Scanning ErrorHandler.cmt Source:ErrorHandler.re
   addValueDeclaration +notify ErrorHandler.re:7:6 path:+ErrorHandler.Make
   addValueDeclaration +x ErrorHandler.re:12:4 path:+ErrorHandler
@@ -1877,6 +1885,7 @@ File References
   DeadValueTest.rei -->> DeadValueTest.re
   Docstrings.re -->> 
   DynamicallyLoadedComponent.re -->> React.re
+  EmptyArray.res -->> React.re, ReactDOMRe.re
   ErrorHandler.re -->> 
   ErrorHandler.rei -->> ErrorHandler.re
   EverythingLiveHere.re -->> 
@@ -2088,6 +2097,8 @@ File References
   Live Value +Docstrings.+one: 0 references () [0]
   Live Value +Docstrings.+signMessage: 0 references () [0]
   Live Value +Docstrings.+flat: 0 references () [0]
+  Live Value +EmptyArray.Z.+emptyArray: 1 references (_none_:1:-1) [0]
+  Live Value +EmptyArray.Z.+make: 1 references (EmptyArray.res:10:9) [0]
   Dead Value +EverythingLiveHere.+z: 0 references () [0]
   Dead Value +EverythingLiveHere.+y: 0 references () [0]
   Dead Value +EverythingLiveHere.+x: 0 references () [0]

examples/deadcode/src/deadcode.txt

@@ -138,7 +138,20 @@ let collectExpr = (super, self, e: Typedtree.expression) => {
   let locFrom = e.exp_loc;
   switch (e.exp_desc) {
   | Texp_ident(_path, _, {Types.val_loc: {loc_ghost: false, _} as locTo}) =>
-    addValueReference(~addFileReference=true, ~locFrom, ~locTo)
+    if (locFrom == locTo && _path |> Path.name == "emptyArray") {
+      // Work around lowercase jsx with no children producing an artifact `emptyArray`
+      // which is called from its own location as many things are generated on the same location.
+      if (Common.Cli.debug^) {
+        Log_.item(
+          "addDummyReference %s --> %s@.",
+          Location.none.loc_start |> posToString,
+          locTo.loc_start |> posToString,
+        );
+      };
+      ValueReferences.add(locTo.loc_start, Location.none.loc_start);
+    } else {
+      addValueReference(~addFileReference=true, ~locFrom, ~locTo);
+    }
 
   | Texp_apply(
       {