webpack/lib/runtime/AsyncModuleGeneratorRuntimeModule.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 AsyncModuleGeneratorRuntimeModule extends HelperRuntimeModule {
	constructor() {
		super("async module generator");
	}

	/**
	 * Generates runtime code for this runtime module.
	 * @returns {string | null} runtime code
	 */
	generate() {
		const compilation = /** @type {Compilation} */ (this.compilation);
		const { runtimeTemplate } = compilation;
		const fn = RuntimeGlobals.asyncModuleGenerator;
		const cst = runtimeTemplate.renderConst();
		// Wrap a generator-based async module body so it drives like an `async`
		// function: run the generator and resolve each `yield`ed dependency
		// promise, without emitting `async`/`await`.
		return Template.asString([
			`${fn} = ${runtimeTemplate.returningFunction(
				runtimeTemplate.basicFunction(
					"__webpack_handle_async_dependencies__, __webpack_async_result__",
					[
						`${cst} gen = body(__webpack_handle_async_dependencies__, __webpack_async_result__);`,
						`${cst} step = ${runtimeTemplate.basicFunction("key, arg", [
							`${cst} info = gen[key](arg);`,
							"if (info.done) return;",
							`Promise.resolve(info.value).then(${runtimeTemplate.expressionFunction(
								'step("next", value)',
								"value"
							)}, ${runtimeTemplate.expressionFunction(
								'step("throw", err)',
								"err"
							)});`
						])};`,
						'step("next");'
					]
				),
				"body"
			)};`
		]);
	}
}

module.exports = AsyncModuleGeneratorRuntimeModule;