chore(build): Generate chunk wrappers

A first pass; this does not have support for a namespace object yet.

scripts/gulpfiles/build_tasks.js

@@ -32,20 +32,34 @@ var {getPackageJson} = require('./helper_tasks');
 //                        Build                           //
 ////////////////////////////////////////////////////////////
 
+/**
+ * Suffix to add to compiled output files.
+ */
+const COMPILED_SUFFIX = '_compressed';
+
 /**
  * A list of chunks.  Order matters: later chunks can depend on
  * earlier ones, but not vice-versa.  All chunks are assumed to depend
  * on the first chunk.
  *
- * Output files will be named <chunk_name>_compressed.js.
+ * The function getChunkOptions will, after running
+ * closure-calculate-chunks, update each chunk to add the following
+ * properties:
+ * 
+ * - .dependencies: a list of the chunks the chunk depends upon.
+ * - .wrapper: the chunk wrapper.
+ *
+ * Output files will be named <chunk.name><COMPILED_SUFFIX>.js.
  */
-const CHUNKS = [
+const chunks = [
   {
     name: 'blockly',
-    entry: 'core/requires.js'
+    entry: 'core/requires.js',
+    namespace: 'Blockly',
   }, {
     name: 'blocks',
-    entry: 'blocks/all.js'
+    entry: 'blocks/all.js',
+    namespace: 'Blockly.blocks',
   }, {
     name: 'javascript',
     entry: 'generators/javascript/all.js',
@@ -460,13 +474,44 @@ function buildLangfiles(done) {
   done();
 };
 
+/**
+ * A helper method to return an closure compiler chunk wrapper that
+ * wraps the compiler output for the given chunk in a Universal Module
+ * Definition.
+ */
+function chunkWrapper(chunk) {
+  const fileNames = chunk.dependencies.map(
+      d => JSON.stringify(`./${d.name}${COMPILED_SUFFIX}.js`));
+  const amdDeps = fileNames.join(', ');
+  const cjsDeps = fileNames.map(f => `require(${f})`).join(', ');
+  const browserDeps =
+      chunk.dependencies.map(d => `root.${d.namespace}`).join(', ');
+  const imports = chunk.dependencies.map(d => d.namespace).join(', ');
+  return `// Do not edit this file; automatically generated.
+
+/* eslint-disable */
+;(function(root, factory) {
+  if (typeof define === 'function' && define.amd) { // AMD
+    define([${amdDeps}], factory);
+  } else if (typeof exports === 'object') { // Node.js
+    module.exports = factory(${cjsDeps});
+  } else { // Browser
+    root.${chunk.namespace} = factory(${browserDeps});
+  }
+}(this, function(${imports}) {
+  %output%
+return ${chunk.namespace};
+}));
+`;
+};
+
 /**
  * Get chunking options to pass to Closure Compiler by using
  * closure-calculate-chunks (hereafter "ccc") to generate them based
  * on the deps.js file (which must be up to date!).
  *
  * The generated options are modified to use the original chunk names
- * given in CHUNKS instead of the entry-point based names used by ccc.
+ * given in chunks instead of the entry-point based names used by ccc.
  *
  * @return {{chunk: !Array<string>, js: !Array<string>}} The chunking
  *     information, in the same form as emitted by
@@ -478,7 +523,7 @@ function getChunkOptions() {
   const cccArgs = [
     '--closure-library-base-js-path ./closure/goog/base.js',
     '--deps-file ./tests/deps.js',
-    ...(CHUNKS.map(chunk => `--entrypoint '${chunk.entry}'`)),
+    ...(chunks.map(chunk => `--entrypoint '${chunk.entry}'`)),
   ];
   const cccCommand = `closure-calculate-chunks ${cccArgs.join(' ')}`;
   const rawOptions= JSON.parse(String(execSync(cccCommand)));
@@ -503,21 +548,32 @@ function getChunkOptions() {
   // This is designed to be passed directly as-is as the options
   // object to the Closure Compiler node API, but we want to replace
   // the unhelpful entry-point based chunk names (let's call these
-  // "nicknames") with the ones from CHUNKS.  Luckily they will be in
+  // "nicknames") with the ones from chunks.  Luckily they will be in
   // the same order that the entry points were supplied in - i.e.,
-  // they correspond 1:1 with the entries in CHUNKS.
+  // they correspond 1:1 with the entries in chunks.
   const chunkByNickname = Object.create(null);
   const chunkList = rawOptions.chunk.map((element, index) => {
-    const [nickname, numJsFiles, depNicks] = element.split(':');
-    const chunk = CHUNKS[index];
+    const [nickname, numJsFiles, dependencyNicks] = element.split(':');
+    const chunk = chunks[index];
     chunkByNickname[nickname] = chunk;
-    const depNames = depNicks ?
-        depNicks.split(',').map(nick => chunkByNickname[nick].name) .join(',')
-        : '';
-    return `${chunk.name}:${numJsFiles}:${depNames}`;
+    if (!dependencyNicks) {  // Chunk has no dependencies.
+      chunk.dependencies = [];
+      return `${chunk.name}:${numJsFiles}`;
+    }
+    chunk.dependencies =
+        dependencyNicks.split(',').map(nick => chunkByNickname[nick]);
+    const dependencyNames =
+        chunk.dependencies.map(dependency => dependency.name).join(',');
+    return `${chunk.name}:${numJsFiles}:${dependencyNames}`;
   });
 
-  return {chunk: chunkList, js: rawOptions.js};
+  // Generate a chunk wrapper for each chunk.
+  for (const chunk of chunks) {
+    chunk.wrapper = chunkWrapper(chunk);
+  }
+
+  const chunkWrappers = chunks.map(chunk => `${chunk.name}:${chunk.wrapper}`);
+  return {chunk: chunkList, js: rawOptions.js, chunk_wrapper: chunkWrappers};
 }
 
 /** 
@@ -581,11 +637,11 @@ function buildCompiled(done) {
     hide_warnings_for: 'node_modules',
     // dependency_mode: 'PRUNE',
     externs: ['./externs/svg-externs.js', /* './externs/goog-externs.js' */],
-    output_wrapper: outputWrapperUMD('Blockly', []),
     define: 'Blockly.VERSION="' + packageJson.version + '"',
     chunk: chunkOptions.chunk,
+    chunk_wrapper: chunkOptions.chunk_wrapper,
     // Don't supply the list of source files in chunkOptions.js as an
-    // option to Closure Compiler; instead feed them to gulp.src.
+    // option to Closure Compiler; instead feed them as input via gulp.src.
   };
   if (argv.debug || argv.strict) {
     options.jscomp_error = [...JSCOMP_ERROR];
@@ -602,7 +658,7 @@ function buildCompiled(done) {
       .pipe(gulp.sourcemaps.init())
       .pipe(gulp.rename(flattenCorePaths))
       .pipe(closureCompiler(options, pluginOptions))
-      .pipe(gulp.rename({suffix: '_compressed'}))
+      .pipe(gulp.rename({suffix: COMPILED_SUFFIX}))
       .pipe(gulp.sourcemaps.mapSources(unflattenCorePaths))
       .pipe(
           gulp.sourcemaps.write('.', {includeContent: false, sourceRoot: './'}))