google-closure-library-webpack-plugin

Webpack5 plugin for google-closure-library, inspired from closure-webpack-plugin.

This plugin transpile the Closure module to ES and CommonJS module, no need to install google-closure-compiler.

Now support google-closure-library@<=20220502.0.0, webpack@>=5.21.0, Webpack watch mode and these goog APIs:

• goog.require
  Will be transpiled to ES or CommonJS import statement, depend on the target option.
• goog.provide(deprecated), goog.module and goog.module.declareLegacyNamespace
  Will be transpiled to ES or CommonJS export statement, depend on the target option.

  In addition, goog.provide() creates the object stubs for a namespace (for example, goog.provide("goog.foo.bar") will create the object goog.foo.bar if it does not already exist).

  As above mentioned, goog.provide will expose a global accessible object in the goog.global, you can direct use it and its sub namespaces after goog.require, but the goog.module is completely opposite, its module structure more pure, flat and individual.
• goog.declareModuleId and goog.module.declareNamespace(deprecated)
  Associates an ES or CommonJS module with a Closure module ID so that is available via goog.require, see example esm.
• goog.addDependency
goog.addDependency will be treat as directive and the goog debug loader not work anymore, the only usage of goog.addDependency see section Speedup the Webpack building process with deps file;
• goog.define
  All goog.define expressions that not mentioned in the defs option, will be replaced with its default value, see defs option.

🎉🎉🎉This plugin is still maintained, welcom to create issue if you find bugs or has any expectant feature🎉🎉🎉

Install

npm install google-closure-library-webpack-plugin --save-dev

Examples

Here are many examples that can download, build and run it.

Options

base : optional string type, defaults to node_modules/google-closure-library/closure/goog/base.js

Path to Closure library base.js file, must be absolute or relative from the Webpack context.

sources : required string or array type

List of absolute patterns, or relative from the Webpack context. You can use the negative patterns(start with !) ignore files or directories.
Supported glob features see minimatch#features.

target : optional "esm" or "commonjs", defaults to "esm"

Closure module transform target, "esm" or "commonjs", defaults to "esm".

defs : optional array type

List of string and value to override the goog.define expression in Closure library, e.g. source goog.LOCALE = goog.define('goog.LOCALE', 'en'); will be converted to goog.LOCALE = 'zh'; with defs option defs: [["goog.LOCALE", "zh"]].
If the value part is omitted, its value will be true, the value could be string, boolean and number.
Because limited with my programming skills, i cannot make the defaultValue parameter support more data types, so this functionality will be disallowed outside Closure library modules, but you can still use this option overwrite the goog.* names, recommend the same functionality Webpack DefinePlugin.

warningLevel: optional "hide", "hideLib", "hideUser" and "hide", defaults to "hideLib"

"show" show all warnings, "hidelib" hide warnings in Closure library modules and show warnings in user modules, "hideUser" opposite to "hideLib", "hide" hide all warnings, defualts to "hideLib".

debug.logTransformed : optional boolean type, defaults to false

Enable log transformed Closure module to build directory, defaults to false.

Something important

💊Speedup the Webpack building process with deps file

Everytime when start the building process by the Webpack build command, this plugin will search and parse all files found in the sources options. Obviously, it's very expensive and unnecessary, but if you specific a deps file like the deps.js in Closure library, this plugin will make a quick through and skip the parsing work until its requied by the goog.require statement.
How speedup building process with deps file, see example deps.

💊How test your code, is the goog.testing still work?

No, but you can still use it with goog.addDependency load and execute JsUnit tests in an unbundled, uncompiled browser environment, see example test.
Also you can directly test the Webpack bundle file with mocha and other tools.

💊Influenced symbols in compiled base.js file

• COMPILED will be stripped and replaced with constant true, e.g. this code if(!COMPILED) { } will be converted to if(!true) { };
• goog.DEBUG defaults to false;
• Replace goog.global with Webpack options.output.globalObject;

Error case

TODO: add error case.

TODOS

These features will add to next version.

• ✔ ClosureTree.check;
• More test, test more Closure library modules;
• Check whether unexposed namespace(except Closure library modules) outside PROVIDE and legacy GOOG module has dot serparator, like this:

  // X: in this GOOG module, namespace "a.b.c" not exposed but has dot separator, should error.
  goog.module("a.b.c");

• Check whether unexposed namespce(except Closure library modules) outside PROVIDE and legacy GOOG module duplicate with other exposed namespace, like this:

  // a.js
  // In this GOOG module, namespace "a" not exposed.
  goog.module("a");
  
  // b.js
  // X: in this PROVIDE module, namespace "a.b" exposed and will construct a duplicated implicit namespace "a", should error.
  goog.provide("a.b");

• ClosureModuleParserPlugin support JS/TS/JSX;
• Export ClosureModuleLoader, remove the injection from LoaderPlugin;
• Support soy template?
• Parse annotations?

News

• VSCode extension Closure-Namespace-View has released, use it quickly browse your Closure namespace