webpack/lib/util/handlerKeys.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";

/** @import RuntimeModule from "../RuntimeModule" */

/**
 * The one key a chunk's runtime modules install on a handler map, or `null` when
 * they install several, none, or one a module could not name. Every module states
 * what it installs, so nothing has to be rendered to find out.
 * @param {RuntimeModule} runtimeModule the runtime module rendering the dispatch
 * @param {string} handlers the handler map global
 * @returns {string | null} the sole handler key, or `null`
 */
const getOnlyHandlerKey = (runtimeModule, handlers) => {
	const { chunkGraph, chunk } = runtimeModule;
	if (chunkGraph === undefined || chunk === undefined) return null;
	/** @type {string | null} */
	let only = null;
	for (const module of chunkGraph.getChunkRuntimeModulesIterable(chunk)) {
		// TODO webpack 6: call it directly, every runtime module answers by then. A
		// module built against an older webpack extends a base class without it.
		const installed =
			typeof module.getInstalledChunkHandlers === "function"
				? module.getInstalledChunkHandlers()
				: null;
		// A module that cannot name what it installs leaves every map unknowable.
		if (!Array.isArray(installed)) return null;
		for (const [map, key] of installed) {
			if (map !== handlers) continue;
			if (only !== null && only !== key) return null;
			only = key;
		}
	}
	return only;
};

module.exports.getOnlyHandlerKey = getOnlyHandlerKey;