webpack/lib/runtime/DefinePropertyGettersRuntimeModule.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");

/** @import Compilation from "../Compilation" */
/** @import { ReadOnlyRuntimeRequirements } from "../Module" */

class DefinePropertyGettersRuntimeModule extends HelperRuntimeModule {
	/**
	 * @param {ReadOnlyRuntimeRequirements} runtimeRequirements runtime requirements
	 */
	constructor(runtimeRequirements) {
		super("define property getters");
		/** @type {ReadOnlyRuntimeRequirements} */
		this.runtimeRequirements = runtimeRequirements;
	}

	/**
	 * Returns true, if the runtime module should get it's own scope.
	 * When false, `generate()` must emit complete statements ending with `;`
	 * so a following runtime IIFE is not parsed as a call (ASI).
	 * @returns {boolean} true, if the runtime module should get it's own scope
	 */
	shouldIsolate() {
		return false;
	}

	/**
	 * 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.definePropertyGetters;
		// Only webpack emits the array form, so a build emitting none cannot
		// receive one; the object form stays either way (see the note below).
		const withArray = this.runtimeRequirements.has(
			RuntimeGlobals.definePropertyGettersFromArray
		);
		// TODO webpack 6: remove object format support. Internal code (e.g. ConcatenatedModule)
		// and third-party libraries may still call __webpack_require__.d() with an object.
		const fromObject = [
			"for(var key in definition) {",
			Template.indent([
				`if(${RuntimeGlobals.hasOwnProperty}(definition, key) && !${RuntimeGlobals.hasOwnProperty}(exports, key)) {`,
				Template.indent([
					"Object.defineProperty(exports, key, { enumerable: true, get: definition[key] });"
				]),
				"}"
			]),
			"}"
		];
		return Template.asString([
			"// define getter/value functions for harmony exports",
			`${fn} = ${runtimeTemplate.basicFunction(
				"exports, definition",
				withArray
					? [
							"if(Array.isArray(definition)) {",
							Template.indent([
								"var i = 0;",
								"while(i < definition.length) {",
								Template.indent([
									"var key = definition[i++];",
									"var binding = definition[i++];",
									// The descriptor is built before the own-property check so a
									// value binding consumes its slot either way.
									"var descriptor = binding === 0 ? { enumerable: true, value: definition[i++] } : { enumerable: true, get: binding };",
									`if(!${RuntimeGlobals.hasOwnProperty}(exports, key)) Object.defineProperty(exports, key, descriptor);`
								]),
								"}"
							]),
							"} else {",
							Template.indent(fromObject),
							"}"
						]
					: fromObject
			)};`
		]);
	}
}

module.exports = DefinePropertyGettersRuntimeModule;