webpack/lib/dependencies/LoaderPlugin.js

Packs CommonJs/AMD modules for the browser. Allows to split your codebase into multiple bundles, which can be loaded on demand. Support 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 LoaderDependency = require("./LoaderDependency");
const NormalModule = require("../NormalModule");

/** @typedef {import("../Module")} Module */

/**
 * @callback LoadModuleCallback
 * @param {Error=} err error object
 * @param {string=} source source code
 * @param {object=} map source map
 * @param {Module=} module loaded module if successful
 */

class LoaderPlugin {
	apply(compiler) {
		compiler.hooks.compilation.tap(
			"LoaderPlugin",
			(compilation, { normalModuleFactory }) => {
				compilation.dependencyFactories.set(
					LoaderDependency,
					normalModuleFactory
				);
			}
		);

		compiler.hooks.compilation.tap("LoaderPlugin", compilation => {
			compilation.hooks.normalModuleLoader.tap(
				"LoaderPlugin",
				(loaderContext, module) => {
					/**
					 * @param {string} request the request string to load the module from
					 * @param {LoadModuleCallback} callback callback returning the loaded module or error
					 * @returns {void}
					 */
					loaderContext.loadModule = (request, callback) => {
						const dep = new LoaderDependency(request);
						dep.loc = {
							name: request
						};
						const factory = compilation.dependencyFactories.get(
							dep.constructor
						);
						if (factory === undefined) {
							return callback(
								new Error(
									`No module factory available for dependency type: ${dep.constructor.name}`
								)
							);
						}
						compilation.semaphore.release();
						compilation.addModuleDependencies(
							module,
							[
								{
									factory,
									dependencies: [dep]
								}
							],
							true,
							"lm",
							true,
							err => {
								compilation.semaphore.acquire(() => {
									if (err) {
										return callback(err);
									}
									if (!dep.module) {
										return callback(new Error("Cannot load the module"));
									}
									// TODO consider removing this in webpack 5
									if (dep.module instanceof NormalModule && dep.module.error) {
										return callback(dep.module.error);
									}
									if (!dep.module._source) {
										throw new Error(
											"The module created for a LoaderDependency must have a property _source"
										);
									}
									let source, map;
									const moduleSource = dep.module._source;
									if (moduleSource.sourceAndMap) {
										const sourceAndMap = moduleSource.sourceAndMap();
										map = sourceAndMap.map;
										source = sourceAndMap.source;
									} else {
										map = moduleSource.map();
										source = moduleSource.source();
									}
									if (dep.module.buildInfo.fileDependencies) {
										for (const d of dep.module.buildInfo.fileDependencies) {
											loaderContext.addDependency(d);
										}
									}
									if (dep.module.buildInfo.contextDependencies) {
										for (const d of dep.module.buildInfo.contextDependencies) {
											loaderContext.addContextDependency(d);
										}
									}
									return callback(null, source, map, dep.module);
								});
							}
						);
					};
				}
			);
		});
	}
}
module.exports = LoaderPlugin;