source: frontend/node_modules/webpack/lib/optimize/MangleExportsPlugin.js

/*
        MIT License http://www.opensource.org/licenses/mit-license.php
        Author Tobias Koppers @sokra
*/

"use strict";

const { UsageState } = require("../ExportsInfo");
const {
        NUMBER_OF_IDENTIFIER_CONTINUATION_CHARS,
        NUMBER_OF_IDENTIFIER_START_CHARS,
        numberToIdentifier
} = 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 */
/** @typedef {import("../util/concatenate").UsedNames} UsedNames */

/**
 * Defines the comparator type used by this module.
 * @template T
 * @typedef {import("../util/comparators").Comparator<T>} Comparator
 */

/**
 * Checks whether it can mangle.
 * @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
/** @type {Comparator<ExportInfo>} */
const comparator = compareSelect((e) => e.name, compareStringsNumeric);
/**
 * Mangle exports info.
 * @param {boolean} deterministic use deterministic names
 * @param {ExportsInfo} exportsInfo exports info
 * @param {boolean | undefined} isNamespace is namespace object
 * @returns {void}
 */
const mangleExportsInfo = (deterministic, exportsInfo, isNamespace) => {
        if (!canMangle(exportsInfo)) return;
        /** @type {UsedNames} */
        const usedNames = new Set();
        /** @type {ExportInfo[]} */
        const mangleableExports = [];

        // Avoid to renamed exports that are not provided when
        // 1. it's not a namespace export: non-provided exports can be found in prototype chain
        // 2. there are other provided exports and deterministic mode is chosen:
        //    non-provided exports would break the determinism
        let avoidMangleNonProvided = !isNamespace;
        if (!avoidMangleNonProvided && deterministic) {
                for (const exportInfo of exportsInfo.ownedExports) {
                        if (exportInfo.provided !== false) {
                                avoidMangleNonProvided = true;
                                break;
                        }
                }
        }
        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-z0-9_$]/i.test(name)) ||
                                // Don't rename 2 char exports in deterministic mode
                                (deterministic &&
                                        name.length === 2 &&
                                        /^[a-z_$][a-z0-9_$]|^[1-9][0-9]/i.test(name)) ||
                                // Don't rename exports that are not provided
                                (avoidMangleNonProvided && 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,
                                        /** @type {ExportsInfo} */ (exportInfo.exportsInfo),
                                        false
                                );
                        }
                }
        }
        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 {
                /** @type {ExportInfo[]} */
                const usedExports = [];
                /** @type {ExportInfo[]} */
                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) {
                                /** @type {string} */
                                let name;
                                do {
                                        name = numberToIdentifier(i++);
                                } while (usedNames.has(name));
                                exportInfo.setUsedName(name);
                        }
                }
        }
};

const PLUGIN_NAME = "MangleExportsPlugin";

class MangleExportsPlugin {
        /**
         * Creates an instance of MangleExportsPlugin.
         * @param {boolean} deterministic use deterministic names
         */
        constructor(deterministic) {
                /** @type {boolean} */
                this._deterministic = deterministic;
        }

        /**
         * Applies the plugin by registering its hooks on the compiler.
         * @param {Compiler} compiler the compiler instance
         * @returns {void}
         */
        apply(compiler) {
                const { _deterministic: deterministic } = this;
                compiler.hooks.compilation.tap(PLUGIN_NAME, (compilation) => {
                        const moduleGraph = compilation.moduleGraph;
                        compilation.hooks.optimizeCodeGeneration.tap(PLUGIN_NAME, (modules) => {
                                if (compilation.moduleMemCaches) {
                                        throw new Error(
                                                "optimization.mangleExports can't be used with cacheUnaffected as export mangling is a global effect"
                                        );
                                }
                                for (const module of modules) {
                                        const isNamespace =
                                                module.buildMeta && module.buildMeta.exportsType === "namespace";
                                        const exportsInfo = moduleGraph.getExportsInfo(module);
                                        mangleExportsInfo(deterministic, exportsInfo, isNamespace);
                                }
                        });
                });
        }
}

module.exports = MangleExportsPlugin;