webpack/lib/runtime/StartupChunkDependenciesPlugin.js

/*
	MIT License http://www.opensource.org/licenses/mit-license.php
*/

"use strict";

const RuntimeGlobals = require("../RuntimeGlobals");
const RuntimeModule = require("../RuntimeModule");
const Template = require("../Template");

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

class StartupChunkDependenciesPlugin {
	/**
	 * @param {Compiler} compiler the compiler instance
	 * @returns {void}
	 */
	apply(compiler) {
		compiler.hooks.thisCompilation.tap(
			"StartupChunkDependenciesPlugin",
			compilation => {
				compilation.hooks.additionalTreeRuntimeRequirements.tap(
					"StartupChunkDependenciesPlugin",
					(chunk, set) => {
						if (compilation.chunkGraph.hasChunkEntryDependentChunks(chunk)) {
							set.add(RuntimeGlobals.startup);
							set.add(RuntimeGlobals.ensureChunk);
							set.add(RuntimeGlobals.ensureChunkIncludeEntries);
							compilation.addRuntimeModule(
								chunk,
								new StartupChunkDependenciesRuntimeModule(
									chunk,
									compilation.chunkGraph
								)
							);
						}
					}
				);
			}
		);
	}
}

class StartupChunkDependenciesRuntimeModule extends RuntimeModule {
	constructor(chunk, chunkGraph) {
		super("startup chunk dependencies");
		this.chunk = chunk;
		this.chunkGraph = chunkGraph;
	}

	/**
	 * @returns {string} runtime code
	 */
	generate() {
		const { chunk, chunkGraph } = this;
		const chunkIds = Array.from(
			chunkGraph.getChunkEntryDependentChunksIterable(chunk)
		).map(chunk => {
			return chunk.id;
		});
		return Template.asString([
			`var next = ${RuntimeGlobals.startup};`,
			`${RuntimeGlobals.startup} = function() {`,
			Template.indent([
				chunkIds.length === 1
					? `return ${RuntimeGlobals.ensureChunk}(${JSON.stringify(
							chunkIds[0]
					  )}).then(next);`
					: chunkIds.length > 2
						? Template.asString([
								// using map is shorter for 3 or more chunks
								`return Promise.all(${JSON.stringify(chunkIds)}.map(${
									RuntimeGlobals.ensureChunk
								}, __webpack_require__)).then(next);`
						  ])
						: Template.asString([
								// 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 = StartupChunkDependenciesPlugin;