[WIP] Working-an-in-it-works closure compiler based compilation for AMP.

- Currently a 15K win on main binary and likely much faster initial JS compilation due to simpler code.
- Includes a compiled compiler binary while we wait for a patch to land that is needed to compiler core-js.
- Doesn't yet activate (and benefit in code size) from type checking.

.travis.yml

@@ -22,6 +22,7 @@ script:
   - gulp build
   - gulp dist
   - gulp presubmit
+  - gulp compile
   # Unit tests with Travis' default chromium
   - gulp test
   # Integration tests with all saucelabs browsers

build-system/tasks/compile.js

@@ -0,0 +1,90 @@
+/**
+ * Copyright 2015 The AMP HTML Authors. 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.
+ */
+
+var closureCompiler = require('gulp-closure-compiler');
+var gulp = require('gulp');
+var rename = require('gulp-rename');
+var uglify = require('gulp-uglify');
+
+// Compiles AMP with the closure compiler. This is intended only for
+// production use. During development we intent to continue using
+// babel, as it has much faster incremental compilation.
+// This currently only works for the main AMP JS binary, but should be
+// straight forward to extend to the rest of our code base.
+gulp.task('compile', function() {
+  /*eslint "google-camelcase/google-camelcase": 0*/
+  return gulp.src([
+    'ads/**/*.js',
+    'extensions/**/*.js',
+    'build/css.js',
+    'src/**/*.js',
+    // We do not want to load the entry point that loads the babel helpers.
+    '!src/amp-babel.js',
+    'builtins/**.js',
+    'third_party/caja/html-sanitizer.js',
+    'third_party/closure-library/sha384-generated.js',
+    'third_party/mustache/**/*.js',
+    'node_modules/document-register-element/build/' +
+        'document-register-element.max.js',
+    'node_modules/core-js/modules/**.js',
+    // Not sure what these files are, but they seem to duplicate code
+    // one level below and confuse the compiler.
+    '!node_modules/core-js/modules/library/**.js',
+    // Don't include tests.
+    '!**_test.js',
+    '!**/test-*.js',
+  ])
+  .pipe(closureCompiler({
+    // Temporary shipping with our own compiler that has a single patch
+    // applied
+    compilerPath: 'third_party/closure-compiler/compiler.jar',
+    fileName: 'build/cc-amp.js',
+    compilerFlags: {
+      // Transpile from ES6 to ES5.
+      language_in: 'ECMASCRIPT6',
+      language_out: 'ECMASCRIPT5',
+      js_module_root: 'node_modules/',
+      common_js_entry_module: 'src/amp.js',
+      process_common_js_modules: true,
+      // This strips all files from the input set that aren't explicitly
+      // required.
+      only_closure_dependencies: true,
+      output_wrapper: '(function(){var process={env:{}};%output%})();'
+    }
+  }))
+  .on('error', function(err) {
+    if (/0 error\(s\)/.test(err.message)) {
+      // emit warning
+      console./*OK*/warn(err.message);
+      this.emit('end');
+    } else {
+      throw err;
+    }
+  })
+  .on('end', function() {
+    console./*OK*/log('Minify closure compiler result');
+    // Somewhat ironically we use uglify to further minify the result.
+    // This is needed because we currently use only very basic optimizations
+    // in closure compiler and it doesn't minify global variables at this
+    // stage.
+    return gulp.src(['build/cc-amp.js'])
+        .pipe(uglify({
+          preserveComments: 'some'
+        }))
+        .pipe(rename('cc-v0.js'))
+        .pipe(gulp.dest('dist'))
+  });
+});

build-system/tasks/index.js

@@ -17,6 +17,7 @@
 require('./babel-helpers');
 require('./changelog');
 require('./clean');
+require('./compile');
 require('./lint');
 require('./make-golden');
 require('./presubmit-checks');

gulpfile.js

@@ -110,7 +110,10 @@ function polyfillsForTests() {
  */
 function compile(watch, shouldMinify) {
   compileCss();
-  compileJs('./src/', 'amp.js', './dist', {
+  // For compilation with babel we start with the amp-babel entry point,
+  // but then rename to the amp.js which we've been using all along.
+  compileJs('./src/', 'amp-babel.js', './dist', {
+    toName: 'amp.js',
     minifiedName: 'v0.js',
     watch: watch,
     minify: shouldMinify,
@@ -418,6 +421,7 @@ function compileJs(srcDir, srcFilename, destDir, options) {
     bundler.bundle()
       .on('error', function(err) { console.error(err); this.emit('end'); })
       .pipe(lazybuild())
+      .pipe(rename(options.toName || srcFilename))
       .pipe(lazywrite());
   }
 

package.json

@@ -40,6 +40,7 @@
     "finalhandler": "0.4.0",
     "fs-extra": "0.26.0",
     "gulp": "3.9.0",
+    "gulp-closure-compiler": "^0.4.0",
     "gulp-eslint": "1.1.0",
     "gulp-exec": "2.1.2",
     "gulp-file": "0.2.0",

src/amp-babel.js

@@ -0,0 +1,21 @@
+/**
+ * Copyright 2015 The AMP HTML Authors. 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.
+ */
+
+// Entry point into AMP for compilation with babel. Just loads amp.js and
+// Babel's helpers.
+
+import '../third_party/babel/custom-babel-helpers';
+import './amp';

src/amp.js

@@ -28,7 +28,7 @@ import {installStyles, makeBodyVisible} from './styles';
 import {installErrorReporting} from './error';
 import {stubElements} from './custom-element';
 import {adopt} from './runtime';
-import {cssText} from '../build/css.js';
+import {cssText} from '../build/css';
 import {action} from './action';
 import {maybeValidate} from './validator-integration';
 

src/error.js

@@ -16,7 +16,7 @@
 
 
 import {getMode} from './mode';
-import {exponentialBackoff} from './exponential-backoff.js';
+import {exponentialBackoff} from './exponential-backoff';
 import {makeBodyVisible} from './styles';
 
 const globalExponentialBackoff = exponentialBackoff(1.5);

src/polyfills.js

@@ -14,11 +14,5 @@
  * limitations under the License.
  */
 
-/**
- * @fileoverview Loads all polyfills needed by the AMP runtime.
- */
-
-
 import 'document-register-element/build/document-register-element.max';
-import '../third_party/babel/custom-babel-helpers';
 import './custom-core-js-shim';

test/_init_tests.js

@@ -15,6 +15,7 @@
  */
 
 // This must load before all other tests.
+import '../third_party/babel/custom-babel-helpers';
 import '../src/polyfills';
 import {adopt} from '../src/runtime';
 

testing/iframe.js

@@ -15,7 +15,6 @@
  */
 
 
-require('../src/polyfills');
 import {Timer} from '../src/timer';
 import {installCoreServices} from '../src/amp-core-service';
 import {registerForUnitTest} from '../src/runtime';