Make webpack benchmark synchronous

jest.config.js

@@ -1,7 +1,13 @@
+// Copyright 2017 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
 const path = require("path");
 
 module.exports = {
-  watchPathIgnorePatterns: [
+  rootDir: path.resolve(__dirname, "src"),
+  transformIgnorePatterns: [
+    "/node_modules/",
     path.resolve(__dirname, "build")
   ]
-}
+};

src/mocks/clear-immediate.js

@@ -0,0 +1,9 @@
+// Copyright 2017 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+const eventLoop = require("./event-loop");
+
+module.exports = task => {
+  eventLoop.cancel(task);
+};

src/mocks/event-loop.js

@@ -0,0 +1,27 @@
+// Copyright 2017 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// This is a very simple event loop implementation. It does not cover the exact behavior
+// in node, especially not the differences between process.nextTick and setImmediate.
+// It is, however, sufficient for the benchmark.
+const tasks = [];
+
+module.exports = {
+  schedule(task) {
+    tasks.push(task);
+  },
+  cancel(task) {
+    const i = tasks.indexOf(task);
+
+    if (i > -1) {
+      tasks.splice(i, 1);
+    }
+  },
+  run() {
+    let task;
+    while ((task = tasks.shift())) {
+      task();
+    }
+  }
+};

src/mocks/process.js

@@ -0,0 +1,24 @@
+// Copyright 2017 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+const eventLoop = require("./event-loop");
+
+exports.nextTick = function(fn) {
+  const args = Array.prototype.slice.call(arguments, 1);
+  eventLoop.schedule(() => {
+    fn.apply(null, args);
+  });
+};
+
+exports.platform = exports.arch = exports.execPath = exports.title = "browser";
+exports.pid = 1;
+exports.browser = true;
+exports.env = {};
+exports.argv = [];
+exports.cwd = () => "/";
+exports.binding = name => {
+  throw new Error("No such module. (Possibly not yet loaded)");
+};
+exports.exit = exports.kill = exports.umask = exports.dlopen = exports.uptime = exports.memoryUsage = exports.uvCounters = () => {};
+exports.features = {};

src/mocks/set-immediate.js

@@ -0,0 +1,14 @@
+// Copyright 2017 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+const eventLoop = require("./event-loop");
+
+module.exports = function(fn) {
+  const args = Array.prototype.slice.call(arguments, 1);
+  const task = () => {
+    fn.apply(null, args);
+  };
+  eventLoop.schedule(task);
+  return task;
+};

src/webpack-benchmark.js

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 const webpack = require("webpack");
+const eventLoop = require("./mocks/event-loop");
 
 const payloads = [
   {
@@ -22,16 +23,27 @@ const payloads = [
 
 module.exports = {
   name: "webpack",
-  defer: true,
-  fn(deferred) {
-    return Promise.all(
-      payloads.map(
-        config =>
-          new Promise((resolve, reject) => {
-            const compiler = webpack(config);
-            compiler.run((err, stats) => void (err ? reject(err) : resolve()));
-          })
-      )
-    ).then(() => deferred.resolve());
+  fn() {
+    payloads.forEach(config => {
+      let finished = false;
+
+      eventLoop.schedule(() => {
+        const compiler = webpack(config);
+        compiler.run((err, stats) => {
+          if (err) {
+            throw err;
+          }
+          if (stats.hasErrors()) {
+            throw stats.compilation.errors[0];
+          }
+          finished = true;
+        });
+      });
+      eventLoop.run();
+
+      if (finished !== true) {
+        throw new Error("Webpack did not finish synchronously");
+      }
+    });
   }
 };

src/webpack-benchmark.test.js

@@ -19,8 +19,7 @@ beforeAll(
     new Promise((resolve, reject) => {
       const baseConfig = webpackConfig[0];
       const config = Object.assign({}, baseConfig, {
-        entry: require.resolve("./webpack-benchmark.js"),
-        bail: true
+        entry: require.resolve("./webpack-benchmark.js")
       });
       config.output = Object.assign({}, baseConfig.output, {
         libraryTarget: "commonjs2",
@@ -39,7 +38,4 @@ beforeAll(
     })
 );
 
-it("webpack runs to completion", () =>
-  new Promise(resolve => {
-    webpackBenchmark.fn({ resolve });
-  }));
+it("webpack runs to completion", () => void webpackBenchmark.fn());

webpack.config.js

@@ -22,10 +22,26 @@ module.exports = [
         "graceful-fs": require.resolve("./src/vfs"),
         module: require.resolve("./src/mocks/dummy"),
         chokidar: require.resolve("./src/mocks/chokidar"),
-        "uglify-js": require.resolve("./src/mocks/dummy")
+        "uglify-js": require.resolve("./src/mocks/dummy"),
+        // These modules are used by virtualfs to fake async fs calls
+        "core-js/library/fn/set-immediate": require.resolve(
+          "./src/mocks/set-immediate"
+        ),
+        "core-js/library/fn/clear-immediate": require.resolve(
+          "./src/mocks/clear-immediate"
+        )
       }
     },
+    node: {
+      setImmediate: false, // this disables also clearImmediate
+      process: false
+    },
     plugins: [
+      new webpack.ProvidePlugin({
+        setImmediate: require.resolve("./src/mocks/set-immediate"),
+        clearImmediate: require.resolve("./src/mocks/clear-immediate"),
+        process: require.resolve("./src/mocks/process")
+      }),
       new webpack.BannerPlugin({
         banner:
           "// Required for JavaScript engine shells.\n" +
@@ -52,10 +68,25 @@ module.exports = [
         "graceful-fs": require.resolve("./src/vfs"),
         module: require.resolve("./src/mocks/dummy"),
         chokidar: require.resolve("./src/mocks/chokidar"),
-        "uglify-js": require.resolve("./src/mocks/dummy")
+        "uglify-js": require.resolve("./src/mocks/dummy"),
+        "core-js/library/fn/set-immediate": require.resolve(
+          "./src/mocks/set-immediate"
+        ),
+        "core-js/library/fn/clear-immediate": require.resolve(
+          "./src/mocks/clear-immediate"
+        )
       }
     },
+    node: {
+      setImmediate: false,
+      process: false
+    },
     plugins: [
+      new webpack.ProvidePlugin({
+        setImmediate: require.resolve("./src/mocks/set-immediate"),
+        clearImmediate: require.resolve("./src/mocks/clear-immediate"),
+        process: require.resolve("./src/mocks/process")
+      }),
       new CopyWebpackPlugin([{ from: "style.css" }, { from: "Logo.png" }]),
       new webpack.BannerPlugin({
         banner: