webpack/lib/dependencies/commonjs/TopLevelThisParserPlugin.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 Alexander Akait @alexander-akait
*/

"use strict";

const RuntimeGlobals = require("../../runtime/RuntimeGlobals");
const ConstDependency = require("../core/ConstDependency");
const ESMExports = require("../esm/ESMExports");

/** @import JavascriptParser, { Range } from "../../javascript/JavascriptParser" */

const GLOBAL_THIS = "globalThis";

const PLUGIN_NAME = "TopLevelThisParserPlugin";

class TopLevelThisParserPlugin {
	/**
	 * Creates an instance of TopLevelThisParserPlugin.
	 * @param {boolean | undefined} hasGlobalThis whether the target has a `globalThis` binding
	 */
	constructor(hasGlobalThis) {
		/** @type {boolean} */
		this.hasGlobalThis = Boolean(hasGlobalThis);
	}

	/**
	 * Applies the plugin by registering its hooks on the compiler.
	 * @param {JavascriptParser} parser the parser
	 * @returns {void}
	 */
	apply(parser) {
		const { hasGlobalThis } = this;

		parser.hooks.expression.for("this").tap(PLUGIN_NAME, (node) => {
			if (!parser.scope.topLevelScope) return;
			// an ES module's top-level `this` is `undefined` whatever the option
			// says, and `ESMTopLevelThisParserPlugin` answers for it
			if (ESMExports.isEnabled(parser.state)) return;
			// a module may declare `globalThis` itself, and the replacement lands
			// in that scope: a bare identifier would read the declaration, or its
			// temporal dead zone, rather than the global object
			const dep =
				hasGlobalThis && parser.getVariableInfo(GLOBAL_THIS) === GLOBAL_THIS
					? new ConstDependency(GLOBAL_THIS, /** @type {Range} */ (node.range))
					: new ConstDependency(
							RuntimeGlobals.global,
							/** @type {Range} */ (node.range),
							[RuntimeGlobals.global]
						);
			dep.loc = parser.getLocation(node);
			parser.state.module.addPresentationalDependency(dep);
			return true;
		});
	}
}

module.exports = TopLevelThisParserPlugin;