webpack/lib/dependencies/CommonJsExportsDependency.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 makeSerializable = require("../util/makeSerializable");
const { propertyAccess } = require("../util/property");
const {
	handleDependencyBase,
	isThisBase,
	isWorkerEntryThis
} = require("./CommonJsDependencyHelpers");
const NullDependency = require("./NullDependency");

/** @import { ReplaceSource } from "webpack-sources" */
/**
 * @import Dependency, {
 * 	ExportsSpec,
 * 	UpdateHashContext,
 * 	ExportInfoName
 * } from "../Dependency"
 */
/** @import Hash from "../util/Hash" */
/** @import { DependencyTemplateContext } from "../DependencyTemplate" */
/** @import ModuleGraph from "../ModuleGraph" */
/** @import { Range } from "../javascript/JavascriptParser" */
/**
 * @import {
 * 	CommonJSDependencyBaseKeywords
 * } from "./CommonJsDependencyHelpers"
 */
/** @typedef {import("../serialization/ObjectMiddleware").ObjectDeserializerContext<[Range, Range | null, CommonJSDependencyBaseKeywords, ExportInfoName[]]>} ObjectDeserializerContext */
/** @typedef {import("../serialization/ObjectMiddleware").ObjectSerializerContext<[Range, Range | null, CommonJSDependencyBaseKeywords, ExportInfoName[]]>} ObjectSerializerContext */

const EMPTY_OBJECT = {};

class CommonJsExportsDependency extends NullDependency {
	/**
	 * Creates an instance of CommonJsExportsDependency.
	 * @param {Range} range range
	 * @param {Range | null} valueRange value range
	 * @param {CommonJSDependencyBaseKeywords} base base
	 * @param {ExportInfoName[]} names names
	 */
	constructor(range, valueRange, base, names) {
		super();
		this.range = range;
		this.valueRange = valueRange;
		/** @type {CommonJSDependencyBaseKeywords} */
		this.base = base;
		/** @type {string[]} */
		this.names = names;
	}

	get type() {
		return "cjs exports";
	}

	/**
	 * Returns the exported names
	 * @param {ModuleGraph} moduleGraph module graph
	 * @returns {ExportsSpec | undefined} export names
	 */
	getExports(moduleGraph) {
		const name = this.names[0];
		return {
			exports: [
				{
					name,
					// we can't mangle names that are in an empty object
					// because one could access the prototype property
					// when export isn't set yet
					canMangle: !(name in EMPTY_OBJECT)
				}
			],
			dependencies: undefined
		};
	}

	/**
	 * Updates the hash with the data contributed by this instance.
	 * @param {Hash} hash hash to be updated
	 * @param {UpdateHashContext} context context
	 * @returns {void}
	 */
	updateHash(hash, context) {
		// a classic worker entry generates `this` as the global scope, so it must
		// not share one code generation with a runtime that generates it as exports
		if (!isThisBase(this.base)) return;
		const { chunkGraph, runtime, runtimeTemplate } = context;
		const module = chunkGraph.moduleGraph.getParentModule(this);
		hash.update(
			module !== undefined &&
				isWorkerEntryThis(module, chunkGraph, runtime, runtimeTemplate)
				? "worker global"
				: "exports"
		);
	}

	/**
	 * Serializes this instance into the provided serializer context.
	 * @param {ObjectSerializerContext} context context
	 */
	serialize(context) {
		context
			.write(this.range)
			.write(this.valueRange)
			.write(this.base)
			.write(this.names);
		super.serialize(context);
	}

	/**
	 * Restores this instance from the provided deserializer context.
	 * @param {ObjectDeserializerContext} context context
	 */
	deserialize(context) {
		this.range = context.read();
		const c1 = context.rest;
		this.valueRange = c1.read();
		const c2 = c1.rest;
		this.base = c2.read();
		const c3 = c2.rest;
		this.names = c3.read();
		super.deserialize(c3.rest);
	}
}

makeSerializable(
	CommonJsExportsDependency,
	"webpack/lib/dependencies/CommonJsExportsDependency"
);

CommonJsExportsDependency.Template = class CommonJsExportsDependencyTemplate extends (
	NullDependency.Template
) {
	/**
	 * Applies the plugin by registering its hooks on the compiler.
	 * @param {Dependency} dependency the dependency for which the template should be applied
	 * @param {ReplaceSource} source the current replace source which can be modified
	 * @param {DependencyTemplateContext} templateContext the context object
	 * @returns {void}
	 */
	apply(
		dependency,
		source,
		{
			module,
			moduleGraph,
			chunkGraph,
			initFragments,
			runtimeRequirements,
			runtime,
			runtimeTemplate
		}
	) {
		const dep = /** @type {CommonJsExportsDependency} */ (dependency);
		// a classic worker entry writes to its global scope, not to an export, so
		// the names stay as written and are never dropped as unused
		const isWorkerEntry =
			isThisBase(dep.base) &&
			isWorkerEntryThis(module, chunkGraph, runtime, runtimeTemplate);
		// CJS exports are never inlined
		const used = isWorkerEntry
			? dep.names
			: /** @type {string | string[] | false} */ (
					moduleGraph.getExportsInfo(module).getUsedName(dep.names, runtime)
				);

		const [type, base] = handleDependencyBase(
			dep.base,
			module,
			runtimeRequirements,
			isWorkerEntry
		);

		switch (type) {
			case "expression":
				if (!used) {
					initFragments.push(
						new InitFragment(
							"var __webpack_unused_export__;\n",
							InitFragment.STAGE_CONSTANTS,
							0,
							"__webpack_unused_export__"
						)
					);
					source.replace(
						dep.range[0],
						dep.range[1] - 1,
						"__webpack_unused_export__"
					);
					return;
				}
				source.replace(
					dep.range[0],
					dep.range[1] - 1,
					`${base}${propertyAccess(/** @type {string[]} */ (used))}`
				);
				return;
			case "Object.defineProperty":
				if (!used) {
					initFragments.push(
						new InitFragment(
							"var __webpack_unused_export__;\n",
							InitFragment.STAGE_CONSTANTS,
							0,
							"__webpack_unused_export__"
						)
					);
					source.replace(
						dep.range[0],
						/** @type {Range} */ (dep.valueRange)[0] - 1,
						"__webpack_unused_export__ = ("
					);
					source.replace(
						/** @type {Range} */ (dep.valueRange)[1],
						dep.range[1] - 1,
						")"
					);
					return;
				}
				source.replace(
					dep.range[0],
					/** @type {Range} */ (dep.valueRange)[0] - 1,
					`Object.defineProperty(${base}${propertyAccess(
						/** @type {string[]} */ (used).slice(0, -1)
					)}, ${JSON.stringify(used[used.length - 1])}, (`
				);
				source.replace(
					/** @type {Range} */ (dep.valueRange)[1],
					dep.range[1] - 1,
					"))"
				);
		}
	}
};

module.exports = CommonJsExportsDependency;