feat(compartment-mapper): support treating top-level return in CJS as a way to export from module

Author: naugtur

packages/compartment-mapper/src/parse-cjs-shared-export-wrapper.js

@@ -184,8 +184,9 @@ export const wrap = ({
 
   freeze(require);
 
-  const afterExecute = () => {
-    const finalExports = module.exports; // in case it's a getter, only call it once
+  const afterExecute = returnValue => {
+    const finalExports =
+      returnValue !== undefined ? returnValue : module.exports; // in case it's a getter, only call it once
     const exportsHaveBeenOverwritten = finalExports !== originalExports;
     // Promotes keys from redefined module.export to top level namespace for import *
     // Note: We could do it less consistently but closer to how node does it if we iterated over exports detected by

packages/compartment-mapper/src/parse-cjs.js

@@ -55,7 +55,7 @@ export const parseCjs = (
     });
 
     // In CommonJS, the top-level `this` is the `module.exports` object.
-    functor.call(
+    const returnValue = functor.call(
       moduleExports,
       require,
       moduleExports,
@@ -64,7 +64,7 @@ export const parseCjs = (
       dirname,
     );
 
-    afterExecute();
+    afterExecute(returnValue);
   };
 
   return {

packages/compartment-mapper/src/parse-pre-cjs.js

@@ -48,7 +48,7 @@ export const parsePreCjs = (
     });
 
     // In CommonJS, the top-level `this` is the `module.exports` object.
-    functor.call(
+    const returnValue = functor.call(
       moduleExports,
       require,
       moduleExports,
@@ -57,7 +57,7 @@ export const parsePreCjs = (
       dirname,
     );
 
-    afterExecute();
+    afterExecute(returnValue);
   };
 
   return {