fix for "module.exports = null" (#532)

CHANGELOG.md

@@ -24,6 +24,10 @@
 
     Previously esbuild always joined the `baseUrl` path to the end of the current directory path. However, if the `baseUrl` was an absolute path, that would end up including the current directory path twice. This situation could arise internally in certain cases involving multiple `tsconfig.json` files and `extends` fields even if the `tsconfig.json` files themselves didn't have absolute paths. Absolute paths are now not modified and should work correctly.
 
+* Fix crash for modules that do `module.exports = null` ([#532](https://github.com/evanw/esbuild/issues/532))
+
+    The code generated by esbuild would crash at run-time if a module overwrote `module.exports` with null or undefined. This has been fixed and no longer crashes.
+
 ## 0.8.9
 
 * Add support for the `mips64le` architecture ([#523](https://github.com/evanw/esbuild/issues/523))

internal/runtime/runtime.go

@@ -87,7 +87,7 @@ func code(isES6 bool) string {
 		}
 		export var __exportStar = (target, module, desc) => {
 			__markAsModule(target)
-			if (typeof module === 'object' || typeof module === 'function')
+			if (module && typeof module === 'object' || typeof module === 'function')
 	`
 
 	// Avoid "let" when not using ES6
@@ -116,7 +116,7 @@ func code(isES6 bool) string {
 			if (module && module.__esModule)
 				return module
 			return __exportStar(
-				__defProp(__create(__getProtoOf(module)), 'default', { value: module, enumerable: true }),
+				__defProp(module != null ? __create(__getProtoOf(module)) : {}, 'default', { value: module, enumerable: true }),
 				module)
 		}
 

scripts/end-to-end-tests.js

@@ -235,6 +235,14 @@
           'in.js': `import * as out from './foo'; if (out.default !== 123) throw 'fail'`,
           'foo.js': `module.exports = 123`,
         }),
+        test(['--bundle', 'in.js', '--outfile=node.js', '--target=' + target].concat(minify), {
+          'in.js': `import * as out from './foo'; if (out.default !== null) throw 'fail'`,
+          'foo.js': `module.exports = null`,
+        }),
+        test(['--bundle', 'in.js', '--outfile=node.js', '--target=' + target].concat(minify), {
+          'in.js': `import * as out from './foo'; if (out.default !== void 0) throw 'fail'`,
+          'foo.js': `module.exports = void 0`,
+        }),
         test(['--bundle', 'in.js', '--outfile=node.js', '--target=' + target].concat(minify), {
           'in.js': `import * as out from './foo'; if (out.foo !== 123) throw 'fail'`,
           'foo.js': `export var foo = 123`,