Fix HMR when adding/renaming assets

Summary:
The HMR logic used to try to calculate the dependencies of every new added (or modified) file, including assets. This resulted in a TransformError.

This commit adds a check that stops the HMR bundling once it finds out that the updated file is an asset

Reviewed By: cpojer

Differential Revision: D5697391

fbshipit-source-id: faf7ccad76ac4922b70ed1c7ce8ce32b03c4e8ee

packages/metro-bundler/src/node-haste/DependencyGraph.js

@@ -224,10 +224,11 @@ class DependencyGraph extends EventEmitter {
     this._haste.end();
   }
 
-  /**
-   * Returns the module object for the given path.
-   */
   getModuleForPath(entryFile: string) {
+    if (this._moduleResolver.isAssetFile(entryFile)) {
+      return this._moduleCache.getAssetModule(entryFile);
+    }
+
     return this._moduleCache.getModule(entryFile);
   }
 

packages/metro-bundler/src/node-haste/DependencyGraph/ModuleResolution.js

@@ -364,12 +364,16 @@ class ModuleResolver<TModule: Moduleish, TPackage: Packageish> {
     return failedFor({file: fileResult.candidates, dir: dirResult.candidates});
   }
 
+  isAssetFile(filename: string): boolean {
+    return this._options.helpers.isAssetFile(filename);
+  }
+
   _loadAsFile(
     dirPath: string,
     fileNameHint: string,
     platform: string | null,
   ): Resolution<TModule, FileCandidates> {
-    if (this._options.helpers.isAssetFile(fileNameHint)) {
+    if (this.isAssetFile(fileNameHint)) {
       return this._loadAsAssetFile(dirPath, fileNameHint, platform);
     }
     const {doesFileExist} = this._options;

packages/metro-bundler/src/node-haste/__tests__/DependencyGraph-test.js

@@ -6,6 +6,7 @@
  * LICENSE file in the root directory of this source tree. An additional grant
  * of patent rights can be found in the PATENTS file in the same directory.
  *
+ * @emails oncall+javascript_tools
  * @format
  */
 
@@ -5661,6 +5662,44 @@ describe('DependencyGraph', function() {
     });
   });
 
+  describe('getModuleForPath()', () => {
+    let DependencyGraph;
+    let dependencyGraph;
+
+    beforeEach(async () => {
+      setMockFileSystem({
+        root: {
+          'index.js': ``,
+          imgs: {
+            'a.png': '',
+          },
+        },
+      });
+
+      DependencyGraph = require('../DependencyGraph');
+      dependencyGraph = await DependencyGraph.load({
+        ...defaults,
+        roots: ['/root'],
+      });
+    });
+
+    afterEach(() => {
+      dependencyGraph.end();
+    });
+
+    it('returns correctly a JS module', async () => {
+      const module = dependencyGraph.getModuleForPath('/root/index.js');
+      expect(await module.getName()).toBe('/root/index.js');
+      expect(module.isAsset()).toBe(false);
+    });
+
+    it('returns correctly an asset module', async () => {
+      const module = dependencyGraph.getModuleForPath('/root/imgs/a.png');
+      expect(await module.getName()).toBe('/root/imgs/a.png');
+      expect(module.isAsset()).toBe(true);
+    });
+  });
+
   /**
    * When running a test on the dependency graph, watch mode is enabled by
    * default, so we must end the watcher to ensure the test does not hang up