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Merge pull request webpack#7344 from asapach/master
feat: support tree shaking in DllPlugin
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‎examples/dll-entry-only/README.md

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# Dll scope hoisting
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[DllPlugin documentation](https://webpack.js.org/plugins/dll-plugin)
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This example demonstrates the usage of `entryOnly` option in combination with module concatenation / scope hoisting.
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By default `DllPlugin` exposes all the modules referenced in the bundle as separate entries.
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The manifest includes the individual modules available for use by `DllReferencePlugin`.
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Since all the modules are being accounted for, this prevents advanced optimizations such as tree shaking.
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The `entryOnly` flag tells `DllPlugin` to only expose the modules which are configured as entry points;
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this affects both the manifest and the resulting bundle.
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Since some of the modules are no longer included in the "public contract" of the Dll,
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they can be optimized by merging (concatenating) multiple modules together or removing unused code.
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This allows to take advantage of tree shaking (scope hoisting and dead code removal) optimizations.
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In this example only `example.js` module is exposed, since it's the entry point.
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Modules `a.js` and `b.js` are concatenated into `example.js`.
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Module `cjs.js` is left as is, since it's in CommonJS format.
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The manifest includes `example.js` as the only exposed module and lists the exports as `["a","b","c"]`
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from the corresponding modules `a.js`, `b.js` and `cjs.js`. None of the other modules are exposed.
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Also see [tree shaking](https://github.com/webpack/webpack/tree/master/examples/harmony-unused)
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and [scope hoisting example](https://github.com/webpack/webpack/tree/master/examples/scope-hoisting).
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# example.js
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``` javascript
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export { a, b } from "./a";
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export { c } from "./cjs";
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```
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# webpack.config.js
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``` javascript
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var path = require("path");
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var webpack = require("../../");
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module.exports = {
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// mode: "development" || "production",
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entry: {
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dll: ["./example"]
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},
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output: {
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path: path.join(__dirname, "dist"),
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filename: "[name].js",
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library: "[name]_[hash]"
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},
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optimization: {
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concatenateModules: true // this is enabled by default in production mode
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},
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plugins: [
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new webpack.DllPlugin({
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path: path.join(__dirname, "dist", "[name]-manifest.json"),
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name: "[name]_[hash]",
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entryOnly: true
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})
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]
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};
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```
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# dist/dll.js
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``` javascript
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var dll_3392692e94d8b928900f =
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```
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<details><summary><code>/******/ (function(modules) { /* webpackBootstrap */ })</code></summary>
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``` js
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/******/ (function(modules) { // webpackBootstrap
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/******/ // The module cache
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/******/ var installedModules = {};
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/******/
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/******/ // The require function
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/******/ function __webpack_require__(moduleId) {
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/******/
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/******/ // Check if module is in cache
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/******/ if(installedModules[moduleId]) {
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/******/ return installedModules[moduleId].exports;
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/******/ }
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/******/ // Create a new module (and put it into the cache)
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/******/ var module = installedModules[moduleId] = {
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/******/ i: moduleId,
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/******/ l: false,
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/******/ exports: {}
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/******/ };
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/******/
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/******/ // Execute the module function
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/******/ modules[moduleId].call(module.exports, module, module.exports, __webpack_require__);
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/******/
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/******/ // Flag the module as loaded
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/******/ module.l = true;
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/******/
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/******/ // Return the exports of the module
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/******/ return module.exports;
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/******/ }
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/******/
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/******/
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/******/ // expose the modules object (__webpack_modules__)
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/******/ __webpack_require__.m = modules;
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/******/
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/******/ // expose the module cache
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/******/ __webpack_require__.c = installedModules;
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/******/
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/******/ // define getter function for harmony exports
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/******/ __webpack_require__.d = function(exports, name, getter) {
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/******/ if(!__webpack_require__.o(exports, name)) {
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/******/ Object.defineProperty(exports, name, {
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/******/ configurable: false,
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/******/ enumerable: true,
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/******/ get: getter
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/******/ });
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/******/ }
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/******/ };
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/******/
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/******/ // define __esModule on exports
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/******/ __webpack_require__.r = function(exports) {
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/******/ Object.defineProperty(exports, '__esModule', { value: true });
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/******/ };
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/******/
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/******/ // getDefaultExport function for compatibility with non-harmony modules
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/******/ __webpack_require__.n = function(module) {
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/******/ var getter = module && module.__esModule ?
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/******/ function getDefault() { return module['default']; } :
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/******/ function getModuleExports() { return module; };
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/******/ __webpack_require__.d(getter, 'a', getter);
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/******/ return getter;
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/******/ };
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/******/
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/******/ // Object.prototype.hasOwnProperty.call
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/******/ __webpack_require__.o = function(object, property) { return Object.prototype.hasOwnProperty.call(object, property); };
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/******/
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/******/ // __webpack_public_path__
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/******/ __webpack_require__.p = "dist/";
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/******/
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/******/
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/******/ // Load entry module and return exports
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/******/ return __webpack_require__(__webpack_require__.s = 0);
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/******/ })
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/************************************************************************/
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```
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</details>
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``` js
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/******/ ([
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/* 0 */
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/*!***************!*\
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!*** dll dll ***!
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\***************/
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/*! no static exports found */
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/*! ModuleConcatenation bailout: Module is not an ECMAScript module */
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/***/ (function(module, exports, __webpack_require__) {
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module.exports = __webpack_require__;
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/***/ }),
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/* 1 */
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/*!****************!*\
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!*** ./cjs.js ***!
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\****************/
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/*! no static exports found */
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/*! ModuleConcatenation bailout: Module is not an ECMAScript module */
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/***/ (function(module, exports) {
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// module cjs (commonjs)
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exports.c = "c";
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/***/ }),
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/* 2 */
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/*!********************************!*\
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!*** ./example.js + 2 modules ***!
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\********************************/
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/*! exports provided: a, b, c */
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/*! ModuleConcatenation bailout: Cannot concat with ./cjs.js (<- Module is not an ECMAScript module) */
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/***/ (function(module, __webpack_exports__, __webpack_require__) {
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"use strict";
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// CONCATENATED MODULE: ./b.js
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// module b
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function b() {
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return "b";
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}
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// CONCATENATED MODULE: ./a.js
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// module a
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var a = "a";
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// EXTERNAL MODULE: ./cjs.js
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var cjs = __webpack_require__(1);
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// CONCATENATED MODULE: ./example.js
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/* concated harmony reexport */__webpack_require__.d(__webpack_exports__, "a", function() { return a; });
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/* concated harmony reexport */__webpack_require__.d(__webpack_exports__, "b", function() { return b; });
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/* concated harmony reexport */__webpack_require__.d(__webpack_exports__, "c", function() { return cjs["c"]; });
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/***/ })
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/******/ ]);
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```
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# dist/dll-manifest.json
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``` javascript
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{"name":"dll_3392692e94d8b928900f","content":{"./example.js":{"id":2,"buildMeta":{"exportsType":"namespace","providedExports":["a","b","c"]}}}}
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```
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# Info
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## Unoptimized
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```
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Hash: 0a1b2c3d4e5f6a7b8c9d
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Version: webpack 4.8.3
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Asset Size Chunks Chunk Names
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dll.js 4.01 KiB 0 [emitted] dll
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Entrypoint dll = dll.js
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chunk {0} dll.js (dll) 216 bytes [entry] [rendered]
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> dll
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[0] dll dll 12 bytes {0} [built]
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dll entry
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[1] ./cjs.js 42 bytes {0} [built]
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harmony side effect evaluation ./cjs [2] ./example.js + 2 modules 2:0-26
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harmony export imported specifier ./cjs [2] ./example.js + 2 modules 2:0-26
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[2] ./example.js + 2 modules 162 bytes {0} [built]
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[exports: a, b, c]
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single entry ./example [0] dll dll dll:0
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| ./example.js 55 bytes [built]
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| [exports: a, b, c]
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| single entry ./example [0] dll dll dll:0
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| ./a.js 53 bytes [built]
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| [exports: a, b]
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| harmony side effect evaluation ./a ./example.js 1:0-27
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| harmony export imported specifier ./a ./example.js 1:0-27
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| harmony export imported specifier ./a ./example.js 1:0-27
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| ./b.js 49 bytes [built]
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| [exports: b]
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| harmony side effect evaluation ./b ./a.js 3:0-20
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| harmony export imported specifier ./b ./a.js 3:0-20
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```
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## Production mode
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```
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Hash: 0a1b2c3d4e5f6a7b8c9d
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Version: webpack 4.8.3
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Asset Size Chunks Chunk Names
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dll.js 791 bytes 0 [emitted] dll
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Entrypoint dll = dll.js
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chunk {0} dll.js (dll) 216 bytes [entry] [rendered]
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> dll
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[0] ./cjs.js 42 bytes {0} [built]
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[only some exports used: c]
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harmony side effect evaluation ./cjs [1] ./example.js + 2 modules 2:0-26
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harmony export imported specifier ./cjs [1] ./example.js + 2 modules 2:0-26
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[1] ./example.js + 2 modules 162 bytes {0} [built]
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[exports: a, b, c]
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single entry ./example [2] dll dll dll:0
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| ./example.js 55 bytes [built]
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| [exports: a, b, c]
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| single entry ./example [2] dll dll dll:0
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| ./a.js 53 bytes [built]
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| [exports: a, b]
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| [all exports used]
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| harmony side effect evaluation ./a ./example.js 1:0-27
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| harmony export imported specifier ./a ./example.js 1:0-27
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| harmony export imported specifier ./a ./example.js 1:0-27
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| ./b.js 49 bytes [built]
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| [exports: b]
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| [all exports used]
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| harmony side effect evaluation ./b ./a.js 3:0-20
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| harmony export imported specifier ./b ./a.js 3:0-20
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[2] dll dll 12 bytes {0} [built]
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dll entry
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```

‎examples/dll-entry-only/a.js

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// module a
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export var a = "a";
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export * from "./b";

‎examples/dll-entry-only/b.js

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// module b
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export function b() {
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return "b";
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}

‎examples/dll-entry-only/build.js

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global.NO_TARGET_ARGS = true;
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require("../build-common");

‎examples/dll-entry-only/cjs.js

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// module cjs (commonjs)
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exports.c = "c";

‎examples/dll-entry-only/example.js

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export { a, b } from "./a";
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export { c } from "./cjs";

‎examples/dll-entry-only/template.md

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# Dll scope hoisting
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[DllPlugin documentation](https://webpack.js.org/plugins/dll-plugin)
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This example demonstrates the usage of `entryOnly` option in combination with module concatenation / scope hoisting.
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By default `DllPlugin` exposes all the modules referenced in the bundle as separate entries.
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The manifest includes the individual modules available for use by `DllReferencePlugin`.
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Since all the modules are being accounted for, this prevents advanced optimizations such as tree shaking.
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The `entryOnly` flag tells `DllPlugin` to only expose the modules which are configured as entry points;
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this affects both the manifest and the resulting bundle.
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Since some of the modules are no longer included in the "public contract" of the Dll,
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they can be optimized by merging (concatenating) multiple modules together or removing unused code.
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This allows to take advantage of tree shaking (scope hoisting and dead code removal) optimizations.
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In this example only `example.js` module is exposed, since it's the entry point.
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Modules `a.js` and `b.js` are concatenated into `example.js`.
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Module `cjs.js` is left as is, since it's in CommonJS format.
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The manifest includes `example.js` as the only exposed module and lists the exports as `["a","b","c"]`
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from the corresponding modules `a.js`, `b.js` and `cjs.js`. None of the other modules are exposed.
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Also see [tree shaking](https://github.com/webpack/webpack/tree/master/examples/harmony-unused)
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and [scope hoisting example](https://github.com/webpack/webpack/tree/master/examples/scope-hoisting).
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# example.js
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``` javascript
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{{example.js}}
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```
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# webpack.config.js
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``` javascript
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{{webpack.config.js}}
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```
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# dist/dll.js
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``` javascript
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{{dist/dll.js}}
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```
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# dist/dll-manifest.json
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``` javascript
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{{dist/dll-manifest.json}}
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```
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# Info
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## Unoptimized
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```
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{{stdout}}
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```
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## Production mode
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```
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{{production:stdout}}
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```

‎examples/dll-entry-only/webpack.config.js

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var path = require("path");
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var webpack = require("../../");
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module.exports = {
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// mode: "development" || "production",
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entry: {
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dll: ["./example"]
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},
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output: {
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path: path.join(__dirname, "dist"),
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filename: "[name].js",
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library: "[name]_[hash]"
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},
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optimization: {
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concatenateModules: true // this is enabled by default in production mode
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},
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plugins: [
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new webpack.DllPlugin({
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path: path.join(__dirname, "dist", "[name]-manifest.json"),
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name: "[name]_[hash]",
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entryOnly: true
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})
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]
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};

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