webpack/lib/prefetch/ChunkPrefetchFunctionRuntimeModule.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
*/

"use strict";

const RuntimeModule = require("../RuntimeModule");
const Template = require("../Template");
const { getOnlyHandlerKey } = require("../util/handlerKeys");
const { propertyAccess } = require("../util/property");

/** @import Compilation from "../Compilation" */

class ChunkPrefetchFunctionRuntimeModule extends RuntimeModule {
	/**
	 * Returns true, if the runtime module should get it's own scope.
	 * When false, `generate()` must emit complete statements ending with `;`
	 * so a following runtime IIFE is not parsed as a call (ASI).
	 * @returns {boolean} true, if the runtime module should get it's own scope
	 */
	shouldIsolate() {
		return false;
	}

	/**
	 * @param {"prefetch" | "preload"} type "prefetch" or "preload" chunk type function
	 * @param {string | null} runtimeFunction the runtime function name, or `null` where nothing fans out over the handlers
	 * @param {string} runtimeHandlers the runtime handlers
	 */
	constructor(type, runtimeFunction, runtimeHandlers) {
		super(`chunk ${type} function`);
		/** @type {string | null} */
		this.runtimeFunction = runtimeFunction;
		/** @type {string} */
		this.runtimeHandlers = runtimeHandlers;
	}

	/**
	 * The `[handlerMap, key]` pairs this module installs onto a chunk handler map
	 * such as `__webpack_require__.f`, or `null` where it cannot name them.
	 * @returns {[string, string][] | null} installed chunk handlers (do not mutate)
	 */
	getInstalledChunkHandlers() {
		// Reads a map rather than installing onto one, so reading its code back would
		// render it in a cycle.
		return RuntimeModule.NO_CHUNK_HANDLERS;
	}

	/**
	 * Generates runtime code for this runtime module.
	 * @returns {string | null} runtime code
	 */
	generate() {
		const { runtimeFunction, runtimeHandlers } = this;
		const compilation = /** @type {Compilation} */ (this.compilation);
		const { runtimeTemplate } = compilation;
		const only =
			runtimeFunction === null
				? null
				: getOnlyHandlerKey(this, runtimeHandlers);
		return Template.asString([
			`${runtimeHandlers} = {};`,
			...(runtimeFunction === null
				? []
				: [
						`${runtimeFunction} = ${runtimeTemplate.basicFunction("chunkId", [
							// One handler needs no walk over the others, and most chunks carry one.
							only === null
								? // map is shorter than forEach
									`Object.keys(${runtimeHandlers}).map(${runtimeTemplate.basicFunction(
										"key",
										`${runtimeHandlers}[key](chunkId);`
									)});`
								: `${runtimeHandlers}${propertyAccess([only])}(chunkId);`
						])};`
					])
		]);
	}
}

module.exports = ChunkPrefetchFunctionRuntimeModule;