[reat-packager] Switch platform resolution based on query param

Summary:
Currently the platform selection is controlled by the blacklist. However, since we want to use the same server instance for cross-platform development, we need this to be controlled per request.

One outstanding issue, is that the DependencyGraph class wasn't designed that way and it doesn't have a per-request state. This means that with the current design race conditions is possible. If we got a request for a different platfrom while processing the previous request, we may change the outcome of the previous request.

To fix this a larger refactor is needed. I'll follow up a diff to do that.

Finally, so I don't break the universe like last time, I'll leave it up to the RN guys to update the call sites.

packager/react-packager/src/Bundler/index.js

@@ -118,14 +118,14 @@ class Bundler {
     return this._cache.end();
   }
 
-  bundle(main, runModule, sourceMapUrl, isDev) {
+  bundle(main, runModule, sourceMapUrl, isDev, platform) {
     const bundle = new Bundle(sourceMapUrl);
 
     const transformModule = this._transformModule.bind(this, bundle);
     const findEventId = Activity.startEvent('find dependencies');
     let transformEventId;
 
-    return this.getDependencies(main, isDev).then((result) => {
+    return this.getDependencies(main, isDev, platform).then((result) => {
       Activity.endEvent(findEventId);
       transformEventId = Activity.startEvent('transform');
 
@@ -149,8 +149,8 @@ class Bundler {
     this._transformer.invalidateFile(filePath);
   }
 
-  getDependencies(main, isDev) {
-    return this._resolver.getDependencies(main, { dev: isDev });
+  getDependencies(main, isDev, platform) {
+    return this._resolver.getDependencies(main, { dev: isDev, platform });
   }
 
   _transformModule(bundle, module) {

packager/react-packager/src/DependencyResolver/DependencyGraph/index.js

@@ -69,7 +69,7 @@ class DependencyGraph {
   constructor(options) {
     this._opts = validateOpts(options);
     this._hasteMap = Object.create(null);
-    this._immediateResolutionCache = Object.create(null);
+    this._resetResolutionCache();
     this._cache = this._opts.cache;
     this.load();
   }
@@ -109,6 +109,20 @@ class DependencyGraph {
     return this._loading;
   }
 
+  setup({ platform }) {
+    if (platform && this._opts.platforms.indexOf(platform) === -1) {
+      throw new Error('Unrecognized platform: ' + platform);
+    }
+
+    // TODO(amasad): This is a potential race condition. Mutliple requests could
+    // interfere with each other. This needs a refactor to fix -- which will
+    // follow this diff.
+    if (this._platformExt !== platform) {
+      this._resetResolutionCache();
+    }
+    this._platformExt = platform;
+  }
+
   resolveDependency(fromModule, toModuleName) {
     const resHash = resolutionHash(fromModule.path, toModuleName);
 
@@ -250,12 +264,15 @@ class DependencyGraph {
       );
     }
 
+    // `platformExt` could be set in the `setup` method.
+    if (!this._platformExt) {
       const platformExt = getPlatformExt(entryPath);
       if (platformExt && this._opts.platforms.indexOf(platformExt) > -1) {
         this._platformExt = platformExt;
       } else {
         this._platformExt = null;
       }
+    }
 
     return this._moduleCache.getModule(absolutePath);
   }
@@ -563,7 +580,7 @@ class DependencyGraph {
   _processFileChange(type, filePath, root, fstat) {
     // It's really hard to invalidate the right module resolution cache
     // so we just blow it up with every file change.
-    this._immediateResolutionCache = Object.create(null);
+    this._resetResolutionCache();
 
     const absPath = path.join(root, filePath);
     if ((fstat && fstat.isDirectory()) ||
@@ -599,6 +616,10 @@ class DependencyGraph {
       });
     }
   }
+
+  _resetResolutionCache() {
+    this._immediateResolutionCache = Object.create(null);
+  }
 }
 
 function assetName(file, ext) {

packager/react-packager/src/DependencyResolver/index.js

@@ -77,6 +77,10 @@ var getDependenciesValidateOpts = declareOpts({
     type: 'boolean',
     default: true,
   },
+  platform: {
+    type: 'string',
+    required: false,
+  },
 });
 
 HasteDependencyResolver.prototype.getDependencies = function(main, options) {
@@ -85,13 +89,12 @@ HasteDependencyResolver.prototype.getDependencies = function(main, options) {
   var depGraph = this._depGraph;
   var self = this;
 
-  return depGraph
-    .load()
-    .then(() => Promise.all([
+  depGraph.setup({ platform: opts.platform });
+
+  return Promise.all([
     depGraph.getOrderedDependencies(main),
     depGraph.getAsyncDependencies(main),
-    ]))
-    .then(
+  ]).then(
     ([dependencies, asyncDependencies]) => dependencies[0].getName().then(
       mainModuleId => {
         self._prependPolyfillDependencies(

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

@@ -110,7 +110,24 @@ describe('processRequest', () => {
         'index.ios.js',
         true,
         'index.ios.includeRequire.map',
-        true
+        true,
+        undefined
+      );
+    });
+  });
+
+  pit('passes in the platform param', function() {
+    return makeRequest(
+      requestHandler,
+      'index.bundle?platform=ios'
+    ).then(function(response) {
+      expect(response).toEqual('this is the source');
+      expect(Bundler.prototype.bundle).toBeCalledWith(
+        'index.js',
+        true,
+        'index.map',
+        true,
+        'ios',
       );
     });
   });
@@ -241,7 +258,8 @@ describe('processRequest', () => {
         'foo file',
         true,
         undefined,
-        true
+        true,
+        undefined
       );
     });
   });
@@ -253,7 +271,8 @@ describe('processRequest', () => {
         'path/to/foo.js',
         false,
         '/path/to/foo.map',
-        false
+        false,
+        undefined
       );
     });
   });

packager/react-packager/src/Server/index.js

@@ -88,6 +88,10 @@ const bundleOpts = declareOpts({
     type: 'boolean',
     default: false,
   },
+  platform: {
+    type: 'string',
+    required: false,
+  }
 });
 
 class Server {
@@ -152,12 +156,12 @@ class Server {
 
   buildBundle(options) {
     const opts = bundleOpts(options);
-
     return this._bundler.bundle(
       opts.entryFile,
       opts.runModule,
       opts.sourceMapUrl,
-      opts.dev
+      opts.dev,
+      opts.platform
     );
   }
 
@@ -425,6 +429,7 @@ class Server {
         'inlineSourceMap',
         false
       ),
+      platform: urlObj.query.platform,
     };
   }