webpack/lib/optimize/MangleExportsPlugin.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 { UsageState } = require("../ExportsInfo");
const {
	numberToIdentifier,
	NUMBER_OF_IDENTIFIER_START_CHARS,
	NUMBER_OF_IDENTIFIER_CONTINUATION_CHARS
} = require("../Template");
const { assignDeterministicIds } = require("../ids/IdHelpers");
const { compareSelect, compareStringsNumeric } = require("../util/comparators");

/** @typedef {import("../Compiler")} Compiler */
/** @typedef {import("../ExportsInfo")} ExportsInfo */
/** @typedef {import("../ExportsInfo").ExportInfo} ExportInfo */

/**
 * @param {ExportsInfo} exportsInfo exports info
 * @returns {boolean} mangle is possible
 */
const canMangle = exportsInfo => {
	if (exportsInfo.otherExportsInfo.getUsed(undefined) !== UsageState.Unused)
		return false;
	let hasSomethingToMangle = false;
	for (const exportInfo of exportsInfo.exports) {
		if (exportInfo.canMangle === true) {
			hasSomethingToMangle = true;
		}
	}
	return hasSomethingToMangle;
};

// Sort by name
const comparator = compareSelect(e => e.name, compareStringsNumeric);
/**
 * @param {boolean} deterministic use deterministic names
 * @param {ExportsInfo} exportsInfo exports info
 * @returns {void}
 */
const mangleExportsInfo = (deterministic, exportsInfo) => {
	if (!canMangle(exportsInfo)) return;
	const usedNames = new Set();
	/** @type {ExportInfo[]} */
	const mangleableExports = [];
	for (const exportInfo of exportsInfo.ownedExports) {
		const name = exportInfo.name;
		if (!exportInfo.hasUsedName()) {
			if (
				// Can the export be mangled?
				exportInfo.canMangle !== true ||
				// Never rename 1 char exports
				(name.length === 1 && /^[a-zA-Z0-9_$]/.test(name)) ||
				// Don't rename 2 char exports in deterministic mode
				(deterministic &&
					name.length === 2 &&
					/^[a-zA-Z_$][a-zA-Z0-9_$]|^[1-9][0-9]/.test(name)) ||
				// Don't rename exports that are not provided
				exportInfo.provided !== true
			) {
				exportInfo.setUsedName(name);
				usedNames.add(name);
			} else {
				mangleableExports.push(exportInfo);
			}
		}
		if (exportInfo.exportsInfoOwned) {
			const used = exportInfo.getUsed(undefined);
			if (
				used === UsageState.OnlyPropertiesUsed ||
				used === UsageState.Unused
			) {
				mangleExportsInfo(deterministic, exportInfo.exportsInfo);
			}
		}
	}
	if (deterministic) {
		assignDeterministicIds(
			mangleableExports,
			e => e.name,
			comparator,
			(e, id) => {
				const name = numberToIdentifier(id);
				const size = usedNames.size;
				usedNames.add(name);
				if (size === usedNames.size) return false;
				e.setUsedName(name);
				return true;
			},
			[
				NUMBER_OF_IDENTIFIER_START_CHARS,
				NUMBER_OF_IDENTIFIER_START_CHARS *
					NUMBER_OF_IDENTIFIER_CONTINUATION_CHARS
			],
			NUMBER_OF_IDENTIFIER_CONTINUATION_CHARS,
			usedNames.size
		);
	} else {
		const usedExports = [];
		const unusedExports = [];
		for (const exportInfo of mangleableExports) {
			if (exportInfo.getUsed(undefined) === UsageState.Unused) {
				unusedExports.push(exportInfo);
			} else {
				usedExports.push(exportInfo);
			}
		}
		usedExports.sort(comparator);
		unusedExports.sort(comparator);
		let i = 0;
		for (const list of [usedExports, unusedExports]) {
			for (const exportInfo of list) {
				let name;
				do {
					name = numberToIdentifier(i++);
				} while (usedNames.has(name));
				exportInfo.setUsedName(name);
			}
		}
	}
};

class MangleExportsPlugin {
	/**
	 * @param {boolean} deterministic use deterministic names
	 */
	constructor(deterministic) {
		this._deterministic = deterministic;
	}
	/**
	 * Apply the plugin
	 * @param {Compiler} compiler the compiler instance
	 * @returns {void}
	 */
	apply(compiler) {
		const { _deterministic: deterministic } = this;
		compiler.hooks.compilation.tap("MangleExportsPlugin", compilation => {
			const moduleGraph = compilation.moduleGraph;
			compilation.hooks.optimizeCodeGeneration.tap(
				"MangleExportsPlugin",
				modules => {
					for (const module of modules) {
						const exportsInfo = moduleGraph.getExportsInfo(module);
						mangleExportsInfo(deterministic, exportsInfo);
					}
				}
			);
		});
	}
}

module.exports = MangleExportsPlugin;