webpack/lib/runtime/StartupChunkDependenciesRuntimeModule.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 RuntimeGlobals = require("../RuntimeGlobals");
const RuntimeModule = require("../RuntimeModule");
const Template = require("../Template");

/** @typedef {import("../Chunk")} Chunk */
/** @typedef {import("../ChunkGraph")} ChunkGraph */
/** @typedef {import("../Compilation")} Compilation */

class StartupChunkDependenciesRuntimeModule extends RuntimeModule {
	/**
	 * @param {boolean} asyncChunkLoading use async chunk loading
	 */
	constructor(asyncChunkLoading) {
		super("startup chunk dependencies", RuntimeModule.STAGE_TRIGGER);
		this.asyncChunkLoading = asyncChunkLoading;
	}

	/**
	 * @returns {string | null} runtime code
	 */
	generate() {
		const chunkGraph = /** @type {ChunkGraph} */ (this.chunkGraph);
		const chunk = /** @type {Chunk} */ (this.chunk);
		const chunkIds = Array.from(
			chunkGraph.getChunkEntryDependentChunksIterable(chunk)
		).map(chunk => {
			return chunk.id;
		});
		const compilation = /** @type {Compilation} */ (this.compilation);
		const { runtimeTemplate } = compilation;
		return Template.asString([
			`var next = ${RuntimeGlobals.startup};`,
			`${RuntimeGlobals.startup} = ${runtimeTemplate.basicFunction(
				"",
				!this.asyncChunkLoading
					? chunkIds
							.map(
								id => `${RuntimeGlobals.ensureChunk}(${JSON.stringify(id)});`
							)
							.concat("return next();")
					: chunkIds.length === 1
						? `return ${RuntimeGlobals.ensureChunk}(${JSON.stringify(
								chunkIds[0]
							)}).then(next);`
						: chunkIds.length > 2
							? [
									// using map is shorter for 3 or more chunks
									`return Promise.all(${JSON.stringify(chunkIds)}.map(${
										RuntimeGlobals.ensureChunk
									}, ${RuntimeGlobals.require})).then(next);`
								]
							: [
									// calling ensureChunk directly is shorter for 0 - 2 chunks
									"return Promise.all([",
									Template.indent(
										chunkIds
											.map(
												id =>
													`${RuntimeGlobals.ensureChunk}(${JSON.stringify(id)})`
											)
											.join(",\n")
									),
									"]).then(next);"
								]
			)};`
		]);
	}
}

module.exports = StartupChunkDependenciesRuntimeModule;