Fix module.exports (codesandbox#326)

* Fix module.exports

* Add MobX sandbox as test sandbox

* Fix screenshot

Author: CompuIves

generate-test-screenshots.sh

@@ -1,4 +1,4 @@
 #!/bin/bash
-docker run -v $(pwd):/app/ --name test-container -t codesandbox/test yarn start:test && \
+docker run -v $(pwd):/home/circleci/codesandbox-client -w /home/circleci/codesandbox-client --name test-container -t codesandbox/node-puppeteer yarn start:test && \
 id=$(docker inspect --format="{{.Id}}" test-container) && \
 docker exec $(id) yarn test:integrations

packages/app/integration-tests/tests/__image_snapshots__/nOymMxyY-snap.png

@@ -17,6 +17,7 @@ const SANDBOXES = [
   'github/reactjs/redux/tree/master/examples/real-world',
   { id: 'github/CompuIves/codesandbox-presentation', timeout: 60000 },
   'lp5rjr0z4z',
+  'nOymMxyY',
 ];
 
 SANDBOXES.forEach(sandbox => {

packages/app/integration-tests/tests/sandboxes.test.js

@@ -5,10 +5,11 @@ import buildProcess from './utils/process';
 export default function(
   code: string,
   require: Function,
-  exports: Object,
+  module: Object,
   env: Object = {}
 ) {
-  const module = { exports: {} };
+  const exports = module.exports;
+
   const global = window;
   const process = buildProcess(env);
   window.global = global;
@@ -19,12 +20,7 @@ export default function(
     }\n})`;
     (0, eval)(newCode)(require, module, exports, process, global); // eslint-disable-line no-eval
 
-    // Choose either the export of __esModule or node
-    return Object.keys(module.exports || {}).length > 0 ||
-      (module.exports || {}).constructor !== Object ||
-      (module.exports && !exports)
-      ? module.exports
-      : exports;
+    return module.exports;
   } catch (e) {
     e.isEvalError = true;
 

packages/app/src/sandbox/eval/loaders/eval.js

@@ -69,13 +69,9 @@ export type LoaderContext = {
   _module: TranspiledModule, // eslint-disable-line no-use-before-define
 };
 
-class Compilation {
-  exports: any;
-
-  constructor() {
-    this.exports = {};
-  }
-}
+type Compilation = {
+  exports: any,
+};
 
 export default class TranspiledModule {
   module: Module;
@@ -437,9 +433,11 @@ export default class TranspiledModule {
       throw new Error(`${this.module.path} hasn't been transpiled yet.`);
     }
 
-    const module = this.module;
+    const localModule = this.module;
 
-    this.compilation = new Compilation();
+    this.compilation = {
+      exports: {},
+    };
     const transpiledModule = this;
 
     try {
@@ -461,11 +459,11 @@ export default class TranspiledModule {
 
         const requiredTranspiledModule = manager.resolveTranspiledModule(
           aliasedPath,
-          module.path
+          localModule.path
         );
 
-        if (module === requiredTranspiledModule.module) {
-          throw new Error(`${module.path} is importing itself`);
+        if (localModule === requiredTranspiledModule.module) {
+          throw new Error(`${localModule.path} is importing itself`);
         }
 
         // Check if this module has been evaluated before, if so return the exports
@@ -483,12 +481,10 @@ export default class TranspiledModule {
       const exports = evaluate(
         this.source.compiledCode,
         require,
-        this.compilation.exports,
+        this.compilation,
         manager.envVariables
       );
 
-      this.compilation.exports = exports;
-
       return exports;
     } catch (e) {
       e.tModule = e.tModule || transpiledModule;