webpack/lib/async-modules/AwaitDependenciesInitFragment.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 InitFragment = require("../InitFragment");
const RuntimeGlobals = require("../RuntimeGlobals");
const Template = require("../Template");

/** @typedef {import("webpack-sources").Source} Source */
/** @typedef {import("../Generator").GenerateContext} GenerateContext */

/** @typedef {Map<string, string>} Dependencies */

/**
 * Represents AwaitDependenciesInitFragment.
 * @extends {InitFragment<GenerateContext>}
 */
class AwaitDependenciesInitFragment extends InitFragment {
	/**
	 * Creates an instance of AwaitDependenciesInitFragment.
	 * @param {Dependencies} dependencies maps an import var to an async module that needs to be awaited
	 * @param {boolean=} generatorLowered module is emitted as a generator, so use `yield` instead of `await`
	 */
	constructor(dependencies, generatorLowered = false) {
		super(
			undefined,
			InitFragment.STAGE_ASYNC_DEPENDENCIES,
			0,
			"await-dependencies"
		);
		/** @type {Dependencies} */
		this.dependencies = dependencies;
		/** @type {boolean} */
		this.generatorLowered = generatorLowered;
	}

	/**
	 * Merges another await-dependencies fragment into this fragment.
	 * @param {AwaitDependenciesInitFragment} other other AwaitDependenciesInitFragment
	 * @returns {AwaitDependenciesInitFragment} AwaitDependenciesInitFragment
	 */
	merge(other) {
		const dependencies = new Map(other.dependencies);
		for (const [key, value] of this.dependencies) {
			dependencies.set(key, value);
		}
		return new AwaitDependenciesInitFragment(
			dependencies,
			this.generatorLowered || other.generatorLowered
		);
	}

	/**
	 * Returns the source code that will be included as initialization code.
	 * @param {GenerateContext} context context
	 * @returns {string | Source | undefined} the source code that will be included as initialization code
	 */
	getContent({ runtimeRequirements, runtimeTemplate }) {
		runtimeRequirements.add(RuntimeGlobals.module);
		if (this.dependencies.size === 0) {
			return "";
		}

		const importVars = [...this.dependencies.keys()];
		const asyncModuleValues = [...this.dependencies.values()].join(", ");

		// In a generator-lowered module (no `async`/`await`, but generators) the
		// dependency `await` becomes `yield`; the body stays a single scope.
		const suspend = this.generatorLowered ? "yield" : "await";

		const templateInput = [
			`var __webpack_async_dependencies__ = __webpack_handle_async_dependencies__([${asyncModuleValues}]);`
		];

		if (
			this.dependencies.size === 1 ||
			!runtimeTemplate.supportsDestructuring()
		) {
			templateInput.push(
				`var __webpack_async_dependencies_result__ = (__webpack_async_dependencies__.then ? (${suspend} __webpack_async_dependencies__)() : __webpack_async_dependencies__);`
			);
			for (const [index, importVar] of importVars.entries()) {
				templateInput.push(
					`${importVar} = __webpack_async_dependencies_result__[${index}];`
				);
			}
		} else {
			const importVarsStr = importVars.join(", ");

			templateInput.push(
				`([${importVarsStr}] = __webpack_async_dependencies__.then ? (${suspend} __webpack_async_dependencies__)() : __webpack_async_dependencies__);`
			);
		}

		templateInput.push("");

		return Template.asString(templateInput);
	}
}

module.exports = AwaitDependenciesInitFragment;