Add experimental transformer setting for disabling require() renaming (…

…#677)

Summary:
**Summary**

Adds a flag, `unstable_disableModuleWrapping`, that disables wrapping of JS modules and transforming `require(...)` calls to `$$_REQUIRE(dependencyMap[n], ...)`. This is required for plugging in third-party bundlers such as [esbuild](https://esbuild.github.io/).

**Test plan**

A test has been added to ensure that `require()` calls are untouched.

Pull Request resolved: #677

Reviewed By: GijsWeterings

Differential Revision: D29358450

Pulled By: motiz88

fbshipit-source-id: cf5c25f891fc2c2bf87af1e6aa4434db70dc2bb3

packages/metro-config/src/__tests__/__snapshots__/loadConfig-test.js.snap

@@ -131,6 +131,7 @@ Object {
     "unstable_collectDependenciesPath": "metro/src/ModuleGraph/worker/collectDependencies.js",
     "unstable_compactOutput": false,
     "unstable_dependencyMapReservedName": null,
+    "unstable_disableModuleWrapping": false,
     "unstable_disableNormalizePseudoGlobals": false,
     "workerPath": "metro/src/DeltaBundler/Worker",
   },
@@ -272,6 +273,7 @@ Object {
     "unstable_collectDependenciesPath": "metro/src/ModuleGraph/worker/collectDependencies.js",
     "unstable_compactOutput": false,
     "unstable_dependencyMapReservedName": null,
+    "unstable_disableModuleWrapping": false,
     "unstable_disableNormalizePseudoGlobals": false,
     "workerPath": "metro/src/DeltaBundler/Worker",
   },
@@ -413,6 +415,7 @@ Object {
     "unstable_collectDependenciesPath": "metro/src/ModuleGraph/worker/collectDependencies.js",
     "unstable_compactOutput": false,
     "unstable_dependencyMapReservedName": null,
+    "unstable_disableModuleWrapping": false,
     "unstable_disableNormalizePseudoGlobals": false,
     "workerPath": "metro/src/DeltaBundler/Worker",
   },
@@ -554,6 +557,7 @@ Object {
     "unstable_collectDependenciesPath": "metro/src/ModuleGraph/worker/collectDependencies.js",
     "unstable_compactOutput": false,
     "unstable_dependencyMapReservedName": null,
+    "unstable_disableModuleWrapping": false,
     "unstable_disableNormalizePseudoGlobals": false,
     "workerPath": "metro/src/DeltaBundler/Worker",
   },

packages/metro-config/src/defaults/index.js

@@ -119,6 +119,7 @@ const getDefaultValues = (projectRoot: ?string): ConfigT => ({
     unstable_collectDependenciesPath:
       'metro/src/ModuleGraph/worker/collectDependencies.js',
     unstable_dependencyMapReservedName: null,
+    unstable_disableModuleWrapping: false,
     unstable_disableNormalizePseudoGlobals: false,
     unstable_compactOutput: false,
   },

packages/metro-transform-worker/src/__tests__/index-test.js

@@ -62,6 +62,7 @@ const baseConfig: JsTransformerConfig = {
     'metro/src/ModuleGraph/worker/collectDependencies',
   unstable_dependencyMapReservedName: null,
   unstable_compactOutput: false,
+  unstable_disableModuleWrapping: false,
   unstable_disableNormalizePseudoGlobals: false,
 };
 
@@ -266,6 +267,27 @@ it('does not add "use strict" on non-modules', async () => {
   );
 });
 
+it('preserves require() calls when module wrapping is disabled', async () => {
+  const contents = ['require("./c");'].join('\n');
+
+  const result = await Transformer.transform(
+    {
+      ...baseConfig,
+      unstable_disableModuleWrapping: true,
+    },
+    '/root',
+    'local/file.js',
+    contents,
+    {
+      dev: true,
+      type: 'module',
+    },
+  );
+
+  expect(result.output[0].type).toBe('js/module');
+  expect(result.output[0].data.code).toBe('require("./c");');
+});
+
 it('reports filename when encountering unsupported dynamic dependency', async () => {
   const contents = [
     'require("./a");',
@@ -360,6 +382,26 @@ it('minifies a JSON file', async () => {
   );
 });
 
+it('does not wrap a JSON file when disableModuleWrapping is enabled', async () => {
+  expect(
+    (
+      await Transformer.transform(
+        {
+          ...baseConfig,
+          unstable_disableModuleWrapping: true,
+        },
+        '/root',
+        'local/file.json',
+        'arbitrary(code);',
+        {
+          dev: true,
+          type: 'module',
+        },
+      )
+    ).output[0].data.code,
+  ).toBe('module.exports = arbitrary(code);;');
+});
+
 it('transforms a script to JS source and bytecode', async () => {
   const result = await Transformer.transform(
     baseConfig,

packages/metro-transform-worker/src/index.js

@@ -36,7 +36,10 @@ const {
 } = require('metro-source-map');
 import type {TransformResultDependency} from 'metro/src/DeltaBundler';
 import type {AllowOptionalDependencies} from 'metro/src/DeltaBundler/types.flow.js';
-import type {DynamicRequiresBehavior} from 'metro/src/ModuleGraph/worker/collectDependencies';
+import type {
+  DependencyTransformer,
+  DynamicRequiresBehavior,
+} from 'metro/src/ModuleGraph/worker/collectDependencies';
 import type {
   BasicSourceMap,
   FBSourceFunctionMap,
@@ -93,6 +96,7 @@ export type JsTransformerConfig = $ReadOnly<{|
   allowOptionalDependencies: AllowOptionalDependencies,
   unstable_collectDependenciesPath: string,
   unstable_dependencyMapReservedName: ?string,
+  unstable_disableModuleWrapping: boolean,
   unstable_disableNormalizePseudoGlobals: boolean,
   unstable_compactOutput: boolean,
 |}>;
@@ -257,6 +261,14 @@ const compileToBytecode = (
   return HermesCompiler.compile(code, options);
 };
 
+const disabledDependencyTransformer: DependencyTransformer<mixed> = {
+  transformSyncRequire: () => void 0,
+  transformImportCall: () => void 0,
+  transformJSResource: () => void 0,
+  transformPrefetch: () => void 0,
+  transformIllegalDynamicRequire: () => void 0,
+};
+
 class InvalidRequireCallError extends Error {
   innerError: InternalInvalidRequireCallError;
   filename: string;
@@ -372,6 +384,10 @@ async function transformJS(
     try {
       const opts = {
         asyncRequireModulePath: config.asyncRequireModulePath,
+        dependencyTransformer:
+          config.unstable_disableModuleWrapping === true
+            ? disabledDependencyTransformer
+            : undefined,
         dynamicRequires: getDynamicDepsBehavior(
           config.dynamicDepsInPackages,
           file.filename,
@@ -391,13 +407,17 @@ async function transformJS(
       throw error;
     }
 
-    ({ast: wrappedAst} = JsFileWrapping.wrapModule(
-      ast,
-      importDefault,
-      importAll,
-      dependencyMapName,
-      config.globalPrefix,
-    ));
+    if (config.unstable_disableModuleWrapping === true) {
+      wrappedAst = ast;
+    } else {
+      ({ast: wrappedAst} = JsFileWrapping.wrapModule(
+        ast,
+        importDefault,
+        importAll,
+        dependencyMapName,
+        config.globalPrefix,
+      ));
+    }
   }
 
   const minify =
@@ -540,7 +560,10 @@ async function transformJSON(
   file: JSONFile,
   {options, config, projectRoot}: TransformationContext,
 ): Promise<TransformResponse> {
-  let code = JsFileWrapping.wrapJson(file.code, config.globalPrefix);
+  let code =
+    config.unstable_disableModuleWrapping === true
+      ? JsFileWrapping.jsonToCommonJS(file.code)
+      : JsFileWrapping.wrapJson(file.code, config.globalPrefix);
   let map = [];
 
   // TODO: When we can reuse transformJS for JSON, we should not derive `minify` separately.