webpack/lib/ExternalsPlugin.js

Packs ECMAScript/CommonJs/AMD modules for the browser. Allows you to split your codebase into multiple bundles, which can be loaded on demand. Supports loaders to preprocess files, i.e. json, jsx, es7, css, less, ... and your custom stuff.

/*
	MIT License http://www.opensource.org/licenses/mit-license.php
	Author Tobias Koppers @sokra
*/

"use strict";

const { ModuleExternalInitFragment } = require("./ExternalModule");
const ExternalModuleFactoryPlugin = require("./ExternalModuleFactoryPlugin");
const ConcatenatedModule = require("./optimize/ConcatenatedModule");

/** @typedef {import("../declarations/WebpackOptions").ExternalsType} ExternalsType */
/** @typedef {import("../declarations/WebpackOptions").Externals} Externals */
/** @typedef {import("./Compiler")} Compiler */
/** @typedef {import("./ExternalModule").Imported} Imported */
/** @typedef {import("./Dependency")} Dependency */

const PLUGIN_NAME = "ExternalsPlugin";

class ExternalsPlugin {
	/**
	 * Creates an instance of ExternalsPlugin.
	 * @param {ExternalsType | ((dependency: Dependency) => ExternalsType)} type default external type
	 * @param {Externals} externals externals config
	 */
	constructor(type, externals) {
		this.type = type;
		this.externals = externals;
	}

	/**
	 * Applies the plugin by registering its hooks on the compiler.
	 * @param {Compiler} compiler the compiler instance
	 * @returns {void}
	 */
	apply(compiler) {
		compiler.hooks.compile.tap(PLUGIN_NAME, ({ normalModuleFactory }) => {
			new ExternalModuleFactoryPlugin(this.type, this.externals).apply(
				normalModuleFactory
			);
		});

		compiler.hooks.compilation.tap(PLUGIN_NAME, (compilation) => {
			const { concatenatedModuleInfo } =
				ConcatenatedModule.getCompilationHooks(compilation);
			concatenatedModuleInfo.tap(PLUGIN_NAME, (updatedInfo, moduleInfo) => {
				const rawExportMap = updatedInfo.rawExportMap;

				if (!rawExportMap) {
					return;
				}

				const chunkInitFragments = moduleInfo.chunkInitFragments;
				const moduleExternalInitFragments =
					/** @type {ModuleExternalInitFragment[]} */
					(
						chunkInitFragments
							? /** @type {unknown[]} */
								(chunkInitFragments).filter(
									(fragment) => fragment instanceof ModuleExternalInitFragment
								)
							: []
					);

				let initFragmentChanged = false;

				for (const fragment of moduleExternalInitFragments) {
					const imported = fragment.getImported();

					if (Array.isArray(imported)) {
						const newImported =
							/** @type {Imported} */
							(
								imported.map(([specifier, finalName]) => [
									specifier,
									rawExportMap.has(specifier)
										? rawExportMap.get(specifier)
										: finalName
								])
							);
						fragment.setImported(newImported);
						initFragmentChanged = true;
					}
				}

				if (initFragmentChanged) {
					return true;
				}
			});
		});
	}
}

module.exports = ExternalsPlugin;