webpack/lib/container/FallbackModule.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 and Zackary Jackson @ScriptedAlchemy
*/

"use strict";

const { RawSource } = require("webpack-sources");
const Module = require("../Module");
const {
	JAVASCRIPT_TYPE,
	JAVASCRIPT_TYPES
} = require("../ModuleSourceTypeConstants");
const { WEBPACK_MODULE_TYPE_FALLBACK } = require("../ModuleTypeConstants");
const RuntimeGlobals = require("../RuntimeGlobals");
const Template = require("../Template");
const makeSerializable = require("../util/makeSerializable");
const FallbackItemDependency = require("./FallbackItemDependency");

/** @typedef {import("../config/defaults").WebpackOptionsNormalizedWithDefaults} WebpackOptions */
/** @typedef {import("../Chunk")} Chunk */
/** @typedef {import("../Compilation")} Compilation */
/** @typedef {import("../Module").BuildCallback} BuildCallback */
/** @typedef {import("../Module").CodeGenerationContext} CodeGenerationContext */
/** @typedef {import("../Module").CodeGenerationResult} CodeGenerationResult */
/** @typedef {import("../Module").LibIdentOptions} LibIdentOptions */
/** @typedef {import("../Module").LibIdent} LibIdent */
/** @typedef {import("../Module").NameForCondition} NameForCondition */
/** @typedef {import("../Module").NeedBuildCallback} NeedBuildCallback */
/** @typedef {import("../Module").NeedBuildContext} NeedBuildContext */
/** @typedef {import("../Module").Sources} Sources */
/** @typedef {import("../Module").SourceTypes} SourceTypes */
/** @typedef {import("../RequestShortener")} RequestShortener */
/** @typedef {import("../ResolverFactory").ResolverWithOptions} ResolverWithOptions */
/** @typedef {import("../serialization/ObjectMiddleware").ObjectDeserializerContext} ObjectDeserializerContext */
/** @typedef {import("../serialization/ObjectMiddleware").ObjectSerializerContext} ObjectSerializerContext */
/** @typedef {import("../util/fs").InputFileSystem} InputFileSystem */
/** @typedef {import("./RemoteModule").ExternalRequests} ExternalRequests */

const RUNTIME_REQUIREMENTS = new Set([RuntimeGlobals.module]);

class FallbackModule extends Module {
	/**
	 * Creates an instance of FallbackModule.
	 * @param {ExternalRequests} requests list of requests to choose one
	 */
	constructor(requests) {
		super(WEBPACK_MODULE_TYPE_FALLBACK);
		/** @type {ExternalRequests} */
		this.requests = requests;
		/** @type {string} */
		this._identifier = `fallback ${this.requests.join(" ")}`;
	}

	/**
	 * Returns the unique identifier used to reference this module.
	 * @returns {string} a unique identifier of the module
	 */
	identifier() {
		return this._identifier;
	}

	/**
	 * Returns a human-readable identifier for this module.
	 * @param {RequestShortener} requestShortener the request shortener
	 * @returns {string} a user readable identifier of the module
	 */
	readableIdentifier(requestShortener) {
		return this._identifier;
	}

	/**
	 * Gets the library identifier.
	 * @param {LibIdentOptions} options options
	 * @returns {LibIdent | null} an identifier for library inclusion
	 */
	libIdent(options) {
		return `${this.layer ? `(${this.layer})/` : ""}webpack/container/fallback/${
			this.requests[0]
		}/and ${this.requests.length - 1} more`;
	}

	/**
	 * Returns true if the module can be placed in the chunk.
	 * @param {Chunk} chunk the chunk which condition should be checked
	 * @param {Compilation} compilation the compilation
	 * @returns {boolean} true if the module can be placed in the chunk
	 */
	chunkCondition(chunk, { chunkGraph }) {
		return chunkGraph.getNumberOfEntryModules(chunk) > 0;
	}

	/**
	 * Checks whether the module needs to be rebuilt for the current build state.
	 * @param {NeedBuildContext} context context info
	 * @param {NeedBuildCallback} callback callback function, returns true, if the module needs a rebuild
	 * @returns {void}
	 */
	needBuild(context, callback) {
		callback(null, !this.buildInfo);
	}

	/**
	 * Builds the module using the provided compilation context.
	 * @param {WebpackOptions} options webpack options
	 * @param {Compilation} compilation the compilation
	 * @param {ResolverWithOptions} resolver the resolver
	 * @param {InputFileSystem} fs the file system
	 * @param {BuildCallback} callback callback function
	 * @returns {void}
	 */
	build(options, compilation, resolver, fs, callback) {
		this.buildMeta = {};
		this.buildInfo = {
			strict: true
		};

		this.clearDependenciesAndBlocks();
		for (const request of this.requests) {
			this.addDependency(new FallbackItemDependency(request));
		}

		callback();
	}

	/**
	 * Returns the estimated size for the requested source type.
	 * @param {string=} type the source type for which the size should be estimated
	 * @returns {number} the estimated size of the module (must be non-zero)
	 */
	size(type) {
		return this.requests.length * 5 + 42;
	}

	/**
	 * Returns the source types this module can generate.
	 * @returns {SourceTypes} types available (do not mutate)
	 */
	getSourceTypes() {
		return JAVASCRIPT_TYPES;
	}

	/**
	 * Generates code and runtime requirements for this module.
	 * @param {CodeGenerationContext} context context for code generation
	 * @returns {CodeGenerationResult} result
	 */
	codeGeneration({ runtimeTemplate, moduleGraph, chunkGraph }) {
		const ids = this.dependencies.map((dep) =>
			chunkGraph.getModuleId(/** @type {Module} */ (moduleGraph.getModule(dep)))
		);
		const code = Template.asString([
			`var ids = ${JSON.stringify(ids)};`,
			"var error, result, i = 0;",
			`var loop = ${runtimeTemplate.basicFunction("next", [
				"while(i < ids.length) {",
				Template.indent([
					`try { next = ${RuntimeGlobals.require}(ids[i++]); } catch(e) { return handleError(e); }`,
					"if(next) return next.then ? next.then(handleResult, handleError) : handleResult(next);"
				]),
				"}",
				"if(error) throw error;"
			])}`,
			`var handleResult = ${runtimeTemplate.basicFunction("result", [
				"if(result) return result;",
				"return loop();"
			])};`,
			`var handleError = ${runtimeTemplate.basicFunction("e", [
				"error = e;",
				"return loop();"
			])};`,
			"module.exports = loop();"
		]);
		/** @type {Sources} */
		const sources = new Map();
		sources.set(JAVASCRIPT_TYPE, new RawSource(code));
		return { sources, runtimeRequirements: RUNTIME_REQUIREMENTS };
	}

	/**
	 * Serializes this instance into the provided serializer context.
	 * @param {ObjectSerializerContext} context context
	 */
	serialize(context) {
		const { write } = context;
		write(this.requests);
		super.serialize(context);
	}

	/**
	 * Restores this instance from the provided deserializer context.
	 * @param {ObjectDeserializerContext} context context
	 * @returns {FallbackModule} deserialized fallback module
	 */
	static deserialize(context) {
		const { read } = context;
		const obj = new FallbackModule(read());
		obj.deserialize(context);
		return obj;
	}
}

makeSerializable(FallbackModule, "webpack/lib/container/FallbackModule");

module.exports = FallbackModule;