Node 6 support (puppeteer#484)

This patch:
- introduces a transpiler which substitutes async/await logic with
generators.
- starts using the transpiler to generate a node6-compatible version of puppeteer
- introduces a runtime-check to decide which version of code to use

Fixes puppeteer#316.

.eslintignore

@@ -1,2 +1,3 @@
 third_party/*
 utils/doclint/check_public_api/test/
+node6/*

.gitignore

@@ -7,3 +7,4 @@
 *.pyc
 .vscode
 package-lock.json
+/node6

.travis.yml

@@ -1,13 +1,10 @@
 language: node_js
-node_js:
-  - "7"
 dist: trusty
 addons:
   apt:
     packages:
       # This is required to run new chrome on old trusty
       - libnss3
-env:
 cache:
   yarn: true
   directories:
@@ -16,6 +13,15 @@ install:
   - yarn install
   # puppeteer's install script downloads Chrome
 script:
-  - yarn run lint
-  - yarn run coverage
-  - yarn run test-phantom
+  - 'if [ "$NODE7" = "true" ]; then yarn run lint; fi'
+  - 'if [ "$NODE7" = "true" ]; then yarn run coverage; fi'
+  - 'if [ "$NODE7" = "true" ]; then yarn run test-phantom; fi'
+  - 'if [ "$NODE6" = "true" ]; then yarn run node6; fi'
+  - 'if [ "$NODE6" = "true" ]; then yarn run test-node6; fi'
+  - 'if [ "$NODE6" = "true" ]; then yarn run node6-sanity; fi'
+jobs:
+  include:
+    - node_js: "7"
+      env: NODE7=true
+    - node_js: "6.4.0"
+      env: NODE6=true

index.js

@@ -14,4 +14,12 @@
  * limitations under the License.
  */
 
-module.exports = require('./lib/Puppeteer');
+// If node does not support async await, use the compiled version.
+let folder = 'lib';
+try {
+  new Function('async function test(){await 1}');
+} catch (error) {
+  folder = 'node6';
+}
+
+module.exports = require(`./${folder}/Puppeteer`);

package.json

@@ -5,18 +5,22 @@
   "main": "index.js",
   "repository": "github:GoogleChrome/puppeteer",
   "engines": {
-    "node": ">=7.10.0"
+    "node": ">=6.4.0"
   },
   "scripts": {
     "unit": "jasmine test/test.js",
     "debug-unit": "DEBUG_TEST=true node --inspect-brk ./node_modules/.bin/jasmine test/test.js",
     "test-phantom": "python third_party/phantomjs/test/run-tests.py",
     "test-doclint": "jasmine utils/doclint/check_public_api/test/test.js && jasmine utils/doclint/preprocessor/test.js",
-    "test": "npm run lint --silent && npm run coverage && npm run test-phantom && npm run test-doclint",
+    "test": "npm run lint --silent && npm run coverage && npm run test-phantom && npm run test-doclint && npm run test-node6",
     "install": "node install.js",
     "lint": "([ \"$CI\" = true ] && eslint --quiet -f codeframe . || eslint .) && npm run doc",
     "doc": "node utils/doclint/cli.js",
-    "coverage": "COVERAGE=true npm run unit"
+    "coverage": "COVERAGE=true npm run unit",
+    "node6": "node utils/node6-transform/index.js",
+    "test-node6": "jasmine utils/node6-transform/test/test.js",
+    "build": "npm run node6",
+    "node6-sanity": "jasmine test/sanity.js"
   },
   "author": "The Chromium Authors",
   "license": "SEE LICENSE IN LICENSE",

test/sanity.js

@@ -0,0 +1,31 @@
+/**
+ * Copyright 2017 Google Inc. All rights reserved.
+ *
+ * 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.
+ */
+
+describe('Puppeteer Sanity', function() {
+  it('should not be insane', function(done) {
+    const puppeteer = require('..');
+    puppeteer.launch().then(browser => {
+      browser.newPage().then(page => {
+        page.goto('data:text/html,hello').then(() => {
+          page.evaluate(() => document.body.textContent).then(content => {
+            expect(content).toBe('hello');
+            done();
+          });
+        });
+      });
+    });
+  });
+});

utils/ChromiumDownloader.js

@@ -85,23 +85,23 @@ module.exports = {
    * @param {?function(number, number)} progressCallback
    * @return {!Promise}
    */
-  downloadRevision: async function(platform, revision, progressCallback) {
+  downloadRevision: function(platform, revision, progressCallback) {
     let url = downloadURLs[platform];
     console.assert(url, `Unsupported platform: ${platform}`);
     url = util.format(url, revision);
     const zipPath = path.join(DOWNLOADS_FOLDER, `download-${platform}-${revision}.zip`);
     const folderPath = getFolderPath(platform, revision);
     if (fs.existsSync(folderPath))
       return;
-    try {
-      if (!fs.existsSync(DOWNLOADS_FOLDER))
-        fs.mkdirSync(DOWNLOADS_FOLDER);
-      await downloadFile(url, zipPath, progressCallback);
-      await extractZip(zipPath, folderPath);
-    } finally {
-      if (fs.existsSync(zipPath))
-        fs.unlinkSync(zipPath);
-    }
+    if (!fs.existsSync(DOWNLOADS_FOLDER))
+      fs.mkdirSync(DOWNLOADS_FOLDER);
+    return downloadFile(url, zipPath, progressCallback)
+        .then(() => extractZip(zipPath, folderPath))
+        .catch(err => err)
+        .then(() => {
+          if (fs.existsSync(zipPath))
+            fs.unlinkSync(zipPath);
+        });
   },
 
   /**
@@ -117,12 +117,13 @@ module.exports = {
   /**
    * @param {string} platform
    * @param {string} revision
+   * @return {!Promise}
    */
-  removeRevision: async function(platform, revision) {
+  removeRevision: function(platform, revision) {
     console.assert(downloadURLs[platform], `Unsupported platform: ${platform}`);
     const folderPath = getFolderPath(platform, revision);
     console.assert(fs.existsSync(folderPath));
-    await new Promise(fulfill => removeRecursive(folderPath, fulfill));
+    return new Promise(fulfill => removeRecursive(folderPath, fulfill));
   },
 
   /**

utils/doclint/check_public_api/JSBuilder.js

@@ -15,7 +15,7 @@
  */
 
 const esprima = require('esprima');
-const ESTreeWalker = require('./ESTreeWalker');
+const ESTreeWalker = require('../../ESTreeWalker');
 const Documentation = require('./Documentation');
 
 class JSOutline {

utils/node6-transform/TransformAsyncFunctions.js

@@ -0,0 +1,114 @@
+/**
+ * Copyright 2017 Google Inc. All rights reserved.
+ *
+ * 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 esprima = require('esprima');
+const ESTreeWalker = require('../ESTreeWalker');
+
+// This is converted from Babel's "transform-async-to-generator"
+// https://babeljs.io/docs/plugins/transform-async-to-generator/
+const asyncToGenerator = fn => {
+  const gen = fn.call(this);
+  return new Promise((resolve, reject) => {
+    function step(key, arg) {
+      let info, value;
+      try {
+        info = gen[key](arg);
+        value = info.value;
+      } catch (error) {
+        reject(error);
+        return;
+      }
+      if (info.done) {
+        resolve(value);
+      } else {
+        return Promise.resolve(value).then(
+            value => {
+              step('next', value);
+            },
+            err => {
+              step('throw', err);
+            });
+      }
+    }
+    return step('next');
+  });
+};
+
+/**
+ * @param {string} text
+ */
+function transformAsyncFunctions(text) {
+  const edits = [];
+
+  const ast = esprima.parseScript(text, {range: true});
+  const walker = new ESTreeWalker(node => {
+    if (node.type === 'FunctionExpression' || node.type === 'FunctionDeclaration' || node.type === 'ArrowFunctionExpression')
+      onFunction(node);
+    else if (node.type === 'AwaitExpression')
+      onAwait(node);
+  });
+  walker.walk(ast);
+
+  edits.sort((a, b) => b.from - a.from);
+  for (const {replacement, from, to} of edits)
+    text = text.substring(0, from) + replacement + text.substring(to);
+
+  return text;
+
+  /**
+   * @param {ESTree.Node} node
+   */
+  function onFunction(node) {
+    if (!node.async) return;
+
+    let range;
+    if (node.parent.type === 'MethodDefinition')
+      range = node.parent.range;
+    else
+      range = node.range;
+    const index = text.substring(range[0], range[1]).indexOf('async') + range[0];
+    insertText(index, index + 'async'.length, '/* async */');
+
+    let before = `{return (${asyncToGenerator.toString()})(function*()`;
+    let after = `);}`;
+    if (node.body.type !== 'BlockStatement') {
+      before += `{ return `;
+      after = `; }` + after;
+    }
+    insertText(node.body.range[0], node.body.range[0], before);
+    insertText(node.body.range[1], node.body.range[1], after);
+  }
+
+  /**
+   * @param {ESTree.Node} node
+   */
+  function onAwait(node) {
+    const index = text.substring(node.range[0], node.range[1]).indexOf('await') + node.range[0];
+    insertText(index, index + 'await'.length, '(yield');
+    insertText(node.range[1], node.range[1], ')');
+  }
+
+  /**
+   * @param {number} from
+   * @param {number} to
+   * @param {string} replacement
+   */
+  function insertText(from, to, replacement) {
+    edits.push({from, to, replacement});
+  }
+}
+
+module.exports = transformAsyncFunctions;

utils/node6-transform/index.js

@@ -0,0 +1,36 @@
+/**
+ * Copyright 2017 Google Inc. All rights reserved.
+ *
+ * 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 fs = require('fs');
+const path = require('path');
+const removeRecursive = require('rimraf').sync;
+const transformAsyncFunctions = require('./TransformAsyncFunctions');
+
+const dirPath = path.join(__dirname, '..', '..', 'lib');
+const outPath = path.join(__dirname, '..', '..', 'node6');
+const fileNames = fs.readdirSync(dirPath);
+const filePaths = fileNames.filter(fileName => fileName.endsWith('.js'));
+
+if (fs.existsSync(outPath))
+  removeRecursive(outPath);
+fs.mkdirSync(outPath);
+
+filePaths.forEach(filePath => {
+  const content = fs.readFileSync(path.join(dirPath, filePath), 'utf8');
+  const output = transformAsyncFunctions(content);
+  fs.writeFileSync(path.resolve(outPath, filePath), output);
+});
+

utils/node6-transform/test/test.js

@@ -0,0 +1,67 @@
+/**
+ * Copyright 2017 Google Inc. All rights reserved.
+ *
+ * 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 transformAsyncFunctions = require('../TransformAsyncFunctions');
+
+describe('TransformAsyncFunctions', function() {
+  it('should convert a function expression', function(done) {
+    const input = `(async function(){ return 123 })()`;
+    const output = eval(transformAsyncFunctions(input));
+    expect(output instanceof Promise).toBe(true);
+    output.then(result => expect(result).toBe(123)).then(done);
+  });
+  it('should convert an arrow function', function(done) {
+    const input = `(async () => 123)()`;
+    const output = eval(transformAsyncFunctions(input));
+    expect(output instanceof Promise).toBe(true);
+    output.then(result => expect(result).toBe(123)).then(done);
+  });
+  it('should convert an arrow function with curly braces', function(done) {
+    const input = `(async () => { return 123 })()`;
+    const output = eval(transformAsyncFunctions(input));
+    expect(output instanceof Promise).toBe(true);
+    output.then(result => expect(result).toBe(123)).then(done);
+  });
+  it('should convert a function declaration', function(done) {
+    const input = `async function f(){ return 123; } f();`;
+    const output = eval(transformAsyncFunctions(input));
+    expect(output instanceof Promise).toBe(true);
+    output.then(result => expect(result).toBe(123)).then(done);
+  });
+  it('should convert await', function(done) {
+    const input = `async function f(){ return 23 + await Promise.resolve(100); } f();`;
+    const output = eval(transformAsyncFunctions(input));
+    expect(output instanceof Promise).toBe(true);
+    output.then(result => expect(result).toBe(123)).then(done);
+  });
+  it('should convert method', function(done) {
+    const input = `class X{async f() { return 123 }} (new X()).f();`;
+    const output = eval(transformAsyncFunctions(input));
+    expect(output instanceof Promise).toBe(true);
+    output.then(result => expect(result).toBe(123)).then(done);
+  });
+  it('should pass arguments', function(done) {
+    const input = `(async function(a, b){ return await a + await b })(Promise.resolve(100), 23)`;
+    const output = eval(transformAsyncFunctions(input));
+    expect(output instanceof Promise).toBe(true);
+    output.then(result => expect(result).toBe(123)).then(done);
+  });
+  it('should still work across eval', function(done) {
+    const input = `var str = (async function(){ return 123; }).toString(); eval('(' + str + ')')();`;
+    const output = eval(transformAsyncFunctions(input));
+    expect(output instanceof Promise).toBe(true);
+    output.then(result => expect(result).toBe(123)).then(done);
+  });
+});