webpack/lib/dependencies/CommonJsExportsDependency.js

Packs CommonJs/AMD modules for the browser. Allows to split your codebase into multiple bundles, which can be loaded on demand. Support 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/propertyAccess");
const { handleDependencyBase } = require("./CommonJsDependencyHelpers");
const NullDependency = require("./NullDependency");

/** @typedef {import("webpack-sources").ReplaceSource} ReplaceSource */
/** @typedef {import("../Dependency")} Dependency */
/** @typedef {import("../Dependency").ExportsSpec} ExportsSpec */
/** @typedef {import("../DependencyTemplate").DependencyTemplateContext} DependencyTemplateContext */
/** @typedef {import("../ModuleGraph")} ModuleGraph */

const EMPTY_OBJECT = {};

class CommonJsExportsDependency extends NullDependency {
	constructor(range, valueRange, base, names) {
		super();
		this.range = range;
		this.valueRange = valueRange;
		this.base = base;
		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
		};
	}

	serialize(context) {
		const { write } = context;
		write(this.range);
		write(this.valueRange);
		write(this.base);
		write(this.names);
		super.serialize(context);
	}

	deserialize(context) {
		const { read } = context;
		this.range = read();
		this.valueRange = read();
		this.base = read();
		this.names = read();
		super.deserialize(context);
	}
}

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

CommonJsExportsDependency.Template = class CommonJsExportsDependencyTemplate extends (
	NullDependency.Template
) {
	/**
	 * @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, initFragments, runtimeRequirements, runtime }
	) {
		const dep = /** @type {CommonJsExportsDependency} */ (dependency);
		const used = moduleGraph
			.getExportsInfo(module)
			.getUsedName(dep.names, runtime);

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

		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(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],
						dep.valueRange[0] - 1,
						"__webpack_unused_export__ = ("
					);
					source.replace(dep.valueRange[1], dep.range[1] - 1, ")");
					return;
				}
				source.replace(
					dep.range[0],
					dep.valueRange[0] - 1,
					`Object.defineProperty(${base}${propertyAccess(
						used.slice(0, -1)
					)}, ${JSON.stringify(used[used.length - 1])}, (`
				);
				source.replace(dep.valueRange[1], dep.range[1] - 1, "))");
				return;
		}
	}
};

module.exports = CommonJsExportsDependency;