refactor(childcompiler): Move fileTimeStampCache out of childCompiler

lib/compiler.js

@@ -45,11 +45,6 @@ class HtmlWebpackChildCompiler {
      * @type {string[]}
      */
     this.fileDependencies = [];
-    /**
-     * Store if the cache was already verified for the given compilation
-     * @type {WeakMap<WebpackCompilation, boolean>}}
-     */
-    this.cacheVerifiedForCompilation = new WeakMap();
   }
 
   /**
@@ -184,37 +179,6 @@ class HtmlWebpackChildCompiler {
 
     return this.compilationPromise;
   }
-
-  /**
-   * Returns `false` if any template file depenendencies has changed
-   * for the given main compilation
-   *
-   * @param {WebpackCompilation} mainCompilation
-   * @returns {boolean}
-   */
-  hasOutDatedTemplateCache (mainCompilation) {
-    // Check if cache validation was already computed
-    const isCacheValid = this.cacheVerifiedForCompilation.get(mainCompilation);
-    if (isCacheValid !== undefined) {
-      return isCacheValid;
-    }
-    // If the compilation was never run there is no invalid cache
-    if (!this.compilationStartedTimestamp) {
-      this.cacheVerifiedForCompilation.set(mainCompilation, false);
-      return false;
-    }
-    // Check if any dependent file was changed after the last compilation
-    const fileTimestamps = mainCompilation.fileTimestamps;
-    const isCacheOutOfDate = this.fileDependencies.some((fileDependency) => {
-      const timestamp = fileTimestamps.get(fileDependency);
-      // If the timestamp is not known the file is new
-      // If the timestamp is larger then the file has changed
-      // Otherwise the file is still the same
-      return !timestamp || timestamp > this.compilationStartedTimestamp;
-    });
-    this.cacheVerifiedForCompilation.set(mainCompilation, isCacheOutOfDate);
-    return isCacheOutOfDate;
-  }
 }
 
 /**
@@ -339,17 +303,6 @@ function compileTemplate (templatePath, outputFilename, mainCompilation) {
   });
 }
 
-/**
- * Returns false if the cache is not valid anymore
- *
- * @param {WebpackCompilation} compilation
- * @returns {boolean}
- */
-function hasOutDatedTemplateCache (compilation) {
-  const childCompiler = childCompilerCache.get(compilation.compiler);
-  return childCompiler ? childCompiler.hasOutDatedTemplateCache(compilation) : false;
-}
-
 /**
  * Return all file dependencies of the last child compilation
  *
@@ -361,6 +314,66 @@ function getFileDependencies (compiler) {
   return childCompiler.fileDependencies;
 }
 
+/**
+ * @type {WeakMap<WebpackCompilation, WeakMap<HtmlWebpackChildCompiler, boolean>>}}
+ */
+const hasOutdatedCompilationDependenciesMap = new WeakMap();
+/**
+ * Returns `true` if the file dependencies of the current childCompiler
+ * for the given mainCompilation are outdated.
+ *
+ * Uses the `hasOutdatedCompilationDependenciesMap` cache if possible.
+ *
+ * @param {WebpackCompilation} mainCompilation
+ * @returns {boolean}
+ */
+function hasOutDatedTemplateCache (mainCompilation) {
+  const childCompiler = getChildCompiler(mainCompilation.compiler);
+  /**
+   * @type {WeakMap<HtmlWebpackChildCompiler, boolean>|undefined}
+   */
+  let hasOutdatedChildCompilerDependenciesMap = hasOutdatedCompilationDependenciesMap.get(mainCompilation);
+  // Create map for childCompiler if none exist
+  if (!hasOutdatedChildCompilerDependenciesMap) {
+    hasOutdatedChildCompilerDependenciesMap = new WeakMap();
+    hasOutdatedCompilationDependenciesMap.set(mainCompilation, hasOutdatedChildCompilerDependenciesMap);
+  }
+  // Try to get the `checkChildCompilerCache` result from cache
+  let isOutdated = hasOutdatedChildCompilerDependenciesMap.get(childCompiler);
+  if (isOutdated !== undefined) {
+    return isOutdated;
+  }
+  // If `checkChildCompilerCache` has never been called for the given
+  // `mainCompilation` and `childCompiler` combination call it:
+  isOutdated = isChildCompilerCacheOutdated(mainCompilation, childCompiler);
+  hasOutdatedChildCompilerDependenciesMap.set(childCompiler, isOutdated);
+  return isOutdated;
+}
+
+/**
+ * Returns `true` if the file dependencies of the given childCompiler are outdated.
+ *
+ * @param {WebpackCompilation} mainCompilation
+ * @param {HtmlWebpackChildCompiler} childCompiler
+ * @returns {boolean}
+ */
+function isChildCompilerCacheOutdated (mainCompilation, childCompiler) {
+  // If the compilation was never run there is no invalid cache
+  if (!childCompiler.compilationStartedTimestamp) {
+    return false;
+  }
+  // Check if any dependent file was changed after the last compilation
+  const fileTimestamps = mainCompilation.fileTimestamps;
+  const isCacheOutOfDate = childCompiler.fileDependencies.some((fileDependency) => {
+    const timestamp = fileTimestamps.get(fileDependency);
+    // If the timestamp is not known the file is new
+    // If the timestamp is larger then the file has changed
+    // Otherwise the file is still the same
+    return !timestamp || timestamp > childCompiler.compilationStartedTimestamp;
+  });
+  return isCacheOutOfDate;
+}
+
 module.exports = {
   addTemplateToCompiler,
   compileTemplate,

spec/caching.spec.js

@@ -39,7 +39,7 @@ function setUpCompiler (htmlWebpackPlugin) {
       path: OUTPUT_DIR,
       filename: 'index_bundle.js'
     },
-    plugins: [htmlWebpackPlugin]
+    plugins: Array.from(arguments)
   };
   const compiler = new WebpackRecompilationSimulator(webpack(webpackConfig));
   return compiler;
@@ -202,6 +202,45 @@ describe('HtmlWebpackPluginCaching', () => {
       .then(done);
   });
 
+  it('should not slow down linear (15 plugins should not take twice as much time as a 1 plugin)', done => {
+    const template = path.join(__dirname, 'fixtures/plain.html');
+    const createHtmlWebpackPlugin = () => new HtmlWebpackPlugin({
+      template: template
+    });
+    let singlePluginCompileStart;
+    let singleCompileRunDuration;
+    let multiPluginComileStart;
+    let multiCompileRunDuration;
+
+    let singleCompiler = setUpCompiler(createHtmlWebpackPlugin());
+    let multiCompiler = setUpCompiler.apply(null, Array(15).fill(0).map(() => createHtmlWebpackPlugin()));
+
+    Promise.resolve()
+      .then(function singleCompileRun () {
+        singlePluginCompileStart = process.hrtime();
+        return singleCompiler.run()
+          // Change the template file and compile again
+          .then(() => {
+            singleCompileRunDuration = process.hrtime(singlePluginCompileStart);
+          });
+      })
+      .then(function multiCompileRun () {
+        multiPluginComileStart = process.hrtime();
+        return multiCompiler.run()
+          // Change the template file and compile again
+          .then(() => {
+            multiCompileRunDuration = process.hrtime(multiPluginComileStart);
+          });
+      }).then(function meassureTime () {
+        const singleCompileRunDurationInNs = singleCompileRunDuration[0] * 1e9 + singleCompileRunDuration[1];
+        const multiCompileRunDurationInNs = multiCompileRunDuration[0] * 1e9 + multiCompileRunDuration[1];
+        const speedComarision = multiCompileRunDurationInNs / singleCompileRunDurationInNs * 100;
+
+        expect(speedComarision).toBeLessThan(200);
+        done();
+      });
+  });
+
   it('should keep watching the webpack html if only a js file was changed', done => {
     const template = path.join(__dirname, 'fixtures/plain.html');
     const jsFile = path.join(__dirname, 'fixtures/index.js');