Webpack + Tree Shaking + Multiple Entry Points

Summary

Webpack correctly drops unused ESnext imports for multiple entry points when they are in completely different configuration objects, but when multiple entry points are within a single entry: configuration, any ESnext exports imported by any of the entry points are imported by all the entry points.

Reproduction steps

$ yarn install
$ yarn build
$ yarn test

Test output:

  tree shaking in webpack4
    array
      one-file
        ✓ app1 should have red, not blue
        ✓ app2 should have blue, not red
      re-export
        ✓ app1 should have red, not blue
        ✓ app2 should have blue, not red
    multiple-entries
      one-file
        1) app1 should have red, not blue
        2) app2 should have blue, not red
      re-export
        3) app1 should have red, not blue
        4) app2 should have blue, not red


  4 passing (22ms)
  4 failing

A Little More Depth

The src directory contains two "scenarios" -- one-file (named exports from a single file) and re-export (named re-exports from further files). Each scenario has two apps, app1.js which uses a common imported red function and app2.js which uses a common imported blue function.

Expectation: Webpack should produce bundles for each app without the unused function.

Actual - Arrays: (WORKS)

A configuration of arrays like webpack.config.arrays.js

const SCENARIOS = ["one-file", "re-export"];
const ENTRY_POINTS = ["app1", "app2"];

module.exports = SCENARIOS
  .map((scenario) => ENTRY_POINTS.map((entryName) => ({
    entry: {
      [entryName]: "./" + entryName + ".js"
    },
  })))
  // Flatten
  .reduce((m, c) => m.concat(c), []);

works and drops the unused functions.

Output bundles at: dist/array

Actual - Multiple Entry Points: (FAILS)

A single configuration object with multiple entry points like webpack.config.multiple-entries.js

const SCENARIOS = ["one-file", "re-export"];

module.exports = SCENARIOS.map((scenario) => ({
  entry: {
    app1: "./app1.js",
    app2: "./app2.js"
  }
}));

does not work. red and blue are included in both app1 and app2 bundles.

Output bundles at: dist/multiple-entries

Maintenance Status

Archived: This project is no longer maintained by Formidable. We are no longer responding to issues or pull requests unless they relate to security concerns. We encourage interested developers to fork this project and make it their own!