Add option for entrpoint + preload/prefetch children

src/index.js

@@ -38,6 +38,7 @@ class PreloadPlugin {
 
     const extractedChunks = extractChunks({
       compilation,
+      rel: options.rel,
       optionsInclude: options.include,
     });
 

src/lib/extract-chunks.js

@@ -15,7 +15,35 @@
  * limitations under the License.
  */
 
-function extractChunks({compilation, optionsInclude}) {
+function getInitialChunks(compilation) {
+  return compilation.chunks.filter(chunk => {
+    if ('canBeInitial' in chunk) {
+      return !chunk.canBeInitial();
+    } else {
+      return !chunk.isInitial();
+    }
+  });
+}
+
+// This is an expensive operation as it uses getStats, but currently it is the only place we can get this data from.
+function extractChildAssets(compilation, rel) {
+  const stats = compilation.getStats().toJson({all: false, entrypoints: true, chunks: true});
+
+  const assets = Object.keys(stats.entrypoints).reduce((childAssets, entrypointKey) => {
+    const entrypoint = stats.entrypoints[entrypointKey];
+    childAssets = childAssets.concat(entrypoint.chunks.map(chunkId => stats.chunks.find(chunk => chunk.id === chunkId)));
+
+    if (entrypoint.childAssets && entrypoint.childAssets[rel]) {
+      childAssets.push({files: entrypoint.childAssets[rel]});
+    }
+
+    return childAssets;
+  }, []);
+
+  return assets;
+}
+
+function extractChunks({compilation, optionsInclude, rel}) {
   try {
     // 'asyncChunks' are chunks intended for lazy/async loading usually generated as
     // part of code-splitting with import() or require.ensure(). By default, asyncChunks
@@ -32,13 +60,11 @@ function extractChunks({compilation, optionsInclude}) {
     }
 
     if (optionsInclude === 'initial') {
-      return compilation.chunks.filter(chunk => {
-        if ('canBeInitial' in chunk) {
-          return chunk.canBeInitial();
-        } else {
-          return chunk.isInitial();
-        }
-      });
+      return getInitialChunks(compilation);
+    }
+
+    if (optionsInclude === 'entryAndChildren') {
+      return extractChildAssets(compilation, rel);
     }
 
     if (optionsInclude === 'allChunks') {

test/unit/extract-chunk.js

@@ -0,0 +1,90 @@
+/**
+ * @license
+ * Copyright 2018 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the 'License');
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an 'AS IS' BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const extractChunk = require('../../src/lib/extract-chunks');
+
+const stubEntrypoints = {
+  entry1: {
+    chunks: ['chunk1', 'chunk2'],
+    childAssets: {}
+  }
+};
+
+const stubEntrypointsWithPreloadedChildren = {
+  entry1: {
+    chunks: ['chunk1', 'chunk2'],
+    childAssets: {}
+  },
+  entry2: {
+    chunks: ['chunk3'],
+    childAssets: {preload: ['file4.js']}
+  }
+};
+
+const stubChunks = [
+  {id: 'chunk1', files: ['file1.js']},
+  {id: 'chunk2', files: ['file2.js']},
+  {id: 'chunk3', files: ['file3.js']},
+];
+
+class StubCompilation {
+  constructor(entrypoints, chunks) {
+    this.entrypoints = entrypoints;
+    this.chunks = chunks;
+  }
+
+  getStats() {
+    return {
+      toJson: () => ({
+        entrypoints: this.entrypoints,
+        chunks: this.chunks
+      })
+    };
+  }
+}
+
+describe(`Entry and Children:`, function() {
+  it(`Includes entrypoints`, function() {
+    const compilation = new StubCompilation(stubEntrypoints, stubChunks);
+    const chunks = extractChunk({
+      compilation,
+      optionsInclude: 'entryAndChildren',
+      rel: 'preload'
+    });
+    expect(chunks).toEqual(stubChunks.slice(0, 2));
+  });
+
+  it(`Includes entrypoints and children`, function() {
+    const compilation = new StubCompilation(stubEntrypointsWithPreloadedChildren, stubChunks);
+    const chunks = extractChunk({
+      compilation,
+      optionsInclude: 'entryAndChildren',
+      rel: 'preload'
+    });
+    expect(chunks).toEqual(stubChunks.concat({files: ['file4.js']}));
+  });
+
+  it(`Only includes entrypoints matching the rel option`, function() {
+    const compilation = new StubCompilation(stubEntrypointsWithPreloadedChildren, stubChunks);
+    const chunks = extractChunk({
+      compilation,
+      optionsInclude: 'entryAndChildren',
+      rel: 'prefetch'
+    });
+    expect(chunks).toEqual(stubChunks);
+  });
+});