pchengxing / webpack-deep-scope-analysis-plugin

A webpack plugin for deep scope analysis

Webpack Deep Scope Analysis Plugin

A webpack plugin for deep scope analysis. It's a project of GSoC 2018 webpack organization.

It's a plugin to improve tree-shaking. It can make webpack eliminate the unused imports related to the unused exports. It solves the issue 6254 for webpack.

Student: @Vincent Mentor: @Tobias

Demo: https://vincentdchan.github.io/webpack-deep-scope-demo/

Install

Install the plugin:

$ yarn add webpack-deep-scope-plugin

Require

• Node.js 8 +
• webpack 4.14.0 +

Usage

Enable the plugin in webpack.config.js:

const WebpackDeepScopeAnalysisPlugin = require('webpack-deep-scope-plugin').default;

module.exports = {
  ...,
  plugins: [
    ...,
    new WebpackDeepScopeAnalysisPlugin(),
  ],
}

Notice: the plugin only works for import and export syntax module. If your code are transpiled to module.export and require syntax, the analyzer can't work correctly.

The plugin will analyze the scope and determine if the variables should be imported automatically.

Articles

Medium

中文版

Pure Annotation

As you know, it's difficult for ECMAScript to analyze the side effects. Hence, PURE annotation is introduced, which is from Uglify:

A function call is marked as "pure" if a comment annotation /*@__PURE__*/ or /*#__PURE__*/ immediately precedes the call. For example: /*@__PURE__*/foo();

Changelog

v1.6.0

• rename package webpack-deep-scope-analysis to deep-scope-analyser, which is published as a new npm package. It's aimed to be a standalone analyser.

v1.5.4

• Fix #7: import * from 'xxx' syntax

v1.5.3

• Fix #5

v1.5.2

• Improve performance and code quality

v1.5.0

• Introduce VirtualScope to simulate module variable

v1.4.0

• Fix #4
• Publish

Contributing

Use lerna to build and test:

$ lerna run build
$ lerna run tslint
$ lerna run test

About Escope

Now the src/ includes a Typescript version of escope, because the plugin needs some internal changes of the escope manager. So I didn't import the escope directly.

When the plugin is nearly finished, I will make some PRs to the original escope repo.