getTransformOptions based on bundle and module

Summary:
Currently, the app server accepts `transformModulePath` which allows us to use different transformation variants. However, these options persist through the lifetime of the server. So we cannot conditionally transform a module differently for two bundles without restarting the server with different options.

`getTransformOptions` basically allows us to change the options to the transformer at runtime based on the bundle and module being transformed.

These options are also used as a cache key for the transformedSource to ensure that if a file is transformed with different options, caching doesn't cause any inconsistencies.

public

Reviewed By: martinbigio

Differential Revision: D2776399

fb-gh-sync-id: 1e0f34d8fa7f0377fcf81f23eb6f3236bd397d56

README.md

@@ -112,6 +112,8 @@ middleware. Takes the following options:
   should be used as a persistent deamon to watch files and update
   itself
 * `assetRoots` array: Where should the packager look for assets
+* `getTransformOptions` function: Middleware to get custom options for the
+  transformer based on the bundle and module being transformed.
 
 ### ReactPackager.buildPackageFromUrl(options, url)
 

react-packager/src/Bundler/Bundle.js

@@ -58,6 +58,10 @@ class Bundle {
     return this._modules;
   }
 
+  getMainModuleId() {
+    return this._mainModuleId;
+  }
+
   setNumPrependedModules(n) {
     this._numPrependedModules = n;
   }

react-packager/src/Bundler/__tests__/Bundler-test.js

@@ -81,6 +81,7 @@ describe('Bundler', function() {
     bundler = new Bundler({
       projectRoots: ['/root'],
       assetServer: assetServer,
+      getTransformOptions: () => ({}),
     });
 
     modules = [

react-packager/src/Bundler/index.js

@@ -135,6 +135,8 @@ class Bundler {
 
     this._projectRoots = opts.projectRoots;
     this._assetServer = opts.assetServer;
+
+    this._getTransformOptions = opts.getTransformOptions;
   }
 
   kill() {
@@ -322,7 +324,8 @@ class Bundler {
       return generateJSONModule(module);
     } else {
       return this._transformer.loadFileAndTransform(
-        path.resolve(module.path)
+        path.resolve(module.path),
+        this._getTransformOptions({bundle, module, platform})
       );
     }
   }

react-packager/src/JSTransformer/index.js

@@ -82,16 +82,18 @@ class Transformer {
     this._cache.invalidate(filePath);
   }
 
-  loadFileAndTransform(filePath) {
+  loadFileAndTransform(filePath, options) {
     if (this._transform == null) {
       return Promise.reject(new Error('No transfrom module'));
     }
 
     debug('transforming file', filePath);
 
+    const optionsJSON = JSON.stringify(options);
+
     return this._cache.get(
       filePath,
-      'transformedSource',
+      'transformedSource-' + optionsJSON,
       // TODO: use fastfs to avoid reading file from disk again
       () => readFile(filePath).then(
         buffer => {
@@ -100,6 +102,7 @@ class Transformer {
           return this._transform({
             sourceCode,
             filename: filePath,
+            options,
           }).then(res => {
             if (res.error) {
               console.warn(

react-packager/src/Server/index.js

@@ -64,6 +64,10 @@ const validateOpts = declareOpts({
     type: 'number',
     required: false,
   },
+  getTransformOptions: {
+    type: 'function',
+    default: () => ({}),
+  }
 });
 
 const bundleOpts = declareOpts({