source: frontend/node_modules/webpack/lib/dependencies/HarmonyExportInitFragment.js

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

"use strict";

const InitFragment = require("../InitFragment");
const RuntimeGlobals = require("../RuntimeGlobals");
const { first } = require("../util/SetHelpers");
const { propertyName } = require("../util/property");

/** @typedef {import("webpack-sources").Source} Source */
/** @typedef {import("../Generator").GenerateContext} GenerateContext */
/** @typedef {import("../ExportsInfo").UsedName} UsedName */

/**
 * Join iterable with comma.
 * @param {Iterable<string>} iterable iterable strings
 * @returns {string} result
 */
const joinIterableWithComma = (iterable) => {
        // This is more performant than Array.from().join(", ")
        // as it doesn't create an array
        let str = "";
        let first = true;
        for (const item of iterable) {
                if (first) {
                        first = false;
                } else {
                        str += ", ";
                }
                str += item;
        }
        return str;
};

/** @typedef {Map<UsedName, string>} ExportMap */
/** @typedef {Set<string>} UnusedExports */

/** @type {ExportMap} */
const EMPTY_MAP = new Map();
/** @type {UnusedExports} */
const EMPTY_SET = new Set();

/**
 * Represents HarmonyExportInitFragment.
 * @extends {InitFragment<GenerateContext>} Context
 */
class HarmonyExportInitFragment extends InitFragment {
        /**
         * Creates an instance of HarmonyExportInitFragment.
         * @param {string} exportsArgument the exports identifier
         * @param {ExportMap} exportMap mapping from used name to exposed variable name
         * @param {UnusedExports} unusedExports list of unused export names
         */
        constructor(
                exportsArgument,
                exportMap = EMPTY_MAP,
                unusedExports = EMPTY_SET
        ) {
                super(undefined, InitFragment.STAGE_HARMONY_EXPORTS, 1, "harmony-exports");
                /** @type {string} */
                this.exportsArgument = exportsArgument;
                /** @type {ExportMap} */
                this.exportMap = exportMap;
                /** @type {UnusedExports} */
                this.unusedExports = unusedExports;
        }

        /**
         * Merges the provided values into a single result.
         * @param {HarmonyExportInitFragment[]} fragments all fragments to merge
         * @returns {HarmonyExportInitFragment} merged fragment
         */
        mergeAll(fragments) {
                /** @type {undefined | ExportMap} */
                let exportMap;
                let exportMapOwned = false;
                /** @type {undefined | UnusedExports} */
                let unusedExports;
                let unusedExportsOwned = false;

                for (const fragment of fragments) {
                        if (fragment.exportMap.size !== 0) {
                                if (exportMap === undefined) {
                                        exportMap = fragment.exportMap;
                                        exportMapOwned = false;
                                } else {
                                        if (!exportMapOwned) {
                                                exportMap = new Map(exportMap);
                                                exportMapOwned = true;
                                        }
                                        for (const [key, value] of fragment.exportMap) {
                                                if (!exportMap.has(key)) exportMap.set(key, value);
                                        }
                                }
                        }
                        if (fragment.unusedExports.size !== 0) {
                                if (unusedExports === undefined) {
                                        unusedExports = fragment.unusedExports;
                                        unusedExportsOwned = false;
                                } else {
                                        if (!unusedExportsOwned) {
                                                unusedExports = new Set(unusedExports);
                                                unusedExportsOwned = true;
                                        }
                                        for (const value of fragment.unusedExports) {
                                                unusedExports.add(value);
                                        }
                                }
                        }
                }
                return new HarmonyExportInitFragment(
                        this.exportsArgument,
                        exportMap,
                        unusedExports
                );
        }

        /**
         * Returns merged result.
         * @param {HarmonyExportInitFragment} other other
         * @returns {HarmonyExportInitFragment} merged result
         */
        merge(other) {
                /** @type {ExportMap} */
                let exportMap;
                if (this.exportMap.size === 0) {
                        exportMap = other.exportMap;
                } else if (other.exportMap.size === 0) {
                        exportMap = this.exportMap;
                } else {
                        exportMap = new Map(other.exportMap);
                        for (const [key, value] of this.exportMap) {
                                if (!exportMap.has(key)) exportMap.set(key, value);
                        }
                }
                /** @type {UnusedExports} */
                let unusedExports;
                if (this.unusedExports.size === 0) {
                        unusedExports = other.unusedExports;
                } else if (other.unusedExports.size === 0) {
                        unusedExports = this.unusedExports;
                } else {
                        unusedExports = new Set(other.unusedExports);
                        for (const value of this.unusedExports) {
                                unusedExports.add(value);
                        }
                }
                return new HarmonyExportInitFragment(
                        this.exportsArgument,
                        exportMap,
                        unusedExports
                );
        }

        /**
         * Returns the source code that will be included as initialization code.
         * @param {GenerateContext} context context
         * @returns {string | Source | undefined} the source code that will be included as initialization code
         */
        getContent({ runtimeTemplate, runtimeRequirements }) {
                runtimeRequirements.add(RuntimeGlobals.exports);
                runtimeRequirements.add(RuntimeGlobals.definePropertyGetters);

                const unusedPart =
                        this.unusedExports.size > 1
                                ? `/* unused harmony exports ${joinIterableWithComma(
                                                this.unusedExports
                                        )} */\n`
                                : this.unusedExports.size > 0
                                        ? `/* unused harmony export ${first(this.unusedExports)} */\n`
                                        : "";
                /** @type {string[]} */
                const definitions = [];
                const orderedExportMap = [...this.exportMap].sort(([a], [b]) =>
                        a < b ? -1 : 1
                );
                for (const [key, value] of orderedExportMap) {
                        definitions.push(
                                `\n/* harmony export */   ${propertyName(
                                        /** @type {string} */ (key)
                                )}: ${runtimeTemplate.returningFunction(value)}`
                        );
                }
                const definePart =
                        this.exportMap.size > 0
                                ? `/* harmony export */ ${RuntimeGlobals.definePropertyGetters}(${
                                                this.exportsArgument
                                        }, {${definitions.join(",")}\n/* harmony export */ });\n`
                                : "";
                return `${definePart}${unusedPart}`;
        }
}

module.exports = HarmonyExportInitFragment;