webpack/lib/runtime/AsyncModuleRuntimeModule.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 RuntimeGlobals = require("../RuntimeGlobals");
const Template = require("../Template");
const HelperRuntimeModule = require("./HelperRuntimeModule");

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

class AsyncModuleRuntimeModule extends HelperRuntimeModule {
	constructor() {
		super("async module");
	}

	/**
	 * @returns {string | null} runtime code
	 */
	generate() {
		const compilation = /** @type {Compilation} */ (this.compilation);
		const { runtimeTemplate } = compilation;
		const fn = RuntimeGlobals.asyncModule;
		return Template.asString([
			'var webpackQueues = typeof Symbol === "function" ? Symbol("webpack queues") : "__webpack_queues__";',
			`var webpackExports = typeof Symbol === "function" ? Symbol("webpack exports") : "${RuntimeGlobals.exports}";`,
			'var webpackError = typeof Symbol === "function" ? Symbol("webpack error") : "__webpack_error__";',
			`var resolveQueue = ${runtimeTemplate.basicFunction("queue", [
				"if(queue && queue.d < 1) {",
				Template.indent([
					"queue.d = 1;",
					`queue.forEach(${runtimeTemplate.expressionFunction(
						"fn.r--",
						"fn"
					)});`,
					`queue.forEach(${runtimeTemplate.expressionFunction(
						"fn.r-- ? fn.r++ : fn()",
						"fn"
					)});`
				]),
				"}"
			])}`,
			`var wrapDeps = ${runtimeTemplate.returningFunction(
				`deps.map(${runtimeTemplate.basicFunction("dep", [
					'if(dep !== null && typeof dep === "object") {',
					Template.indent([
						"if(dep[webpackQueues]) return dep;",
						"if(dep.then) {",
						Template.indent([
							"var queue = [];",
							"queue.d = 0;",
							`dep.then(${runtimeTemplate.basicFunction("r", [
								"obj[webpackExports] = r;",
								"resolveQueue(queue);"
							])}, ${runtimeTemplate.basicFunction("e", [
								"obj[webpackError] = e;",
								"resolveQueue(queue);"
							])});`,
							"var obj = {};",
							`obj[webpackQueues] = ${runtimeTemplate.expressionFunction(
								`fn(queue)`,
								"fn"
							)};`,
							"return obj;"
						]),
						"}"
					]),
					"}",
					"var ret = {};",
					`ret[webpackQueues] = ${runtimeTemplate.emptyFunction()};`,
					"ret[webpackExports] = dep;",
					"return ret;"
				])})`,
				"deps"
			)};`,
			`${fn} = ${runtimeTemplate.basicFunction("module, body, hasAwait", [
				"var queue;",
				"hasAwait && ((queue = []).d = -1);",
				"var depQueues = new Set();",
				"var exports = module.exports;",
				"var currentDeps;",
				"var outerResolve;",
				"var reject;",
				`var promise = new Promise(${runtimeTemplate.basicFunction(
					"resolve, rej",
					["reject = rej;", "outerResolve = resolve;"]
				)});`,
				"promise[webpackExports] = exports;",
				`promise[webpackQueues] = ${runtimeTemplate.expressionFunction(
					`queue && fn(queue), depQueues.forEach(fn), promise["catch"](${runtimeTemplate.emptyFunction()})`,
					"fn"
				)};`,
				"module.exports = promise;",
				`body(${runtimeTemplate.basicFunction("deps", [
					"currentDeps = wrapDeps(deps);",
					"var fn;",
					`var getResult = ${runtimeTemplate.returningFunction(
						`currentDeps.map(${runtimeTemplate.basicFunction("d", [
							"if(d[webpackError]) throw d[webpackError];",
							"return d[webpackExports];"
						])})`
					)}`,
					`var promise = new Promise(${runtimeTemplate.basicFunction(
						"resolve",
						[
							`fn = ${runtimeTemplate.expressionFunction(
								"resolve(getResult)",
								""
							)};`,
							"fn.r = 0;",
							`var fnQueue = ${runtimeTemplate.expressionFunction(
								"q !== queue && !depQueues.has(q) && (depQueues.add(q), q && !q.d && (fn.r++, q.push(fn)))",
								"q"
							)};`,
							`currentDeps.map(${runtimeTemplate.expressionFunction(
								"dep[webpackQueues](fnQueue)",
								"dep"
							)});`
						]
					)});`,
					"return fn.r ? promise : getResult();"
				])}, ${runtimeTemplate.expressionFunction(
					"(err ? reject(promise[webpackError] = err) : outerResolve(exports)), resolveQueue(queue)",
					"err"
				)});`,
				"queue && queue.d < 0 && (queue.d = 0);"
			])};`
		]);
	}
}

module.exports = AsyncModuleRuntimeModule;