source: trip-planner-front/node_modules/enhanced-resolve/lib/AliasFieldPlugin.js

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

"use strict";

const DescriptionFileUtils = require("./DescriptionFileUtils");
const getInnerRequest = require("./getInnerRequest");

/** @typedef {import("./Resolver")} Resolver */
/** @typedef {import("./Resolver").ResolveRequest} ResolveRequest */
/** @typedef {import("./Resolver").ResolveStepHook} ResolveStepHook */

module.exports = class AliasFieldPlugin {
        /**
         * @param {string | ResolveStepHook} source source
         * @param {string | Array<string>} field field
         * @param {string | ResolveStepHook} target target
         */
        constructor(source, field, target) {
                this.source = source;
                this.field = field;
                this.target = target;
        }

        /**
         * @param {Resolver} resolver the resolver
         * @returns {void}
         */
        apply(resolver) {
                const target = resolver.ensureHook(this.target);
                resolver
                        .getHook(this.source)
                        .tapAsync("AliasFieldPlugin", (request, resolveContext, callback) => {
                                if (!request.descriptionFileData) return callback();
                                const innerRequest = getInnerRequest(resolver, request);
                                if (!innerRequest) return callback();
                                const fieldData = DescriptionFileUtils.getField(
                                        request.descriptionFileData,
                                        this.field
                                );
                                if (fieldData === null || typeof fieldData !== "object") {
                                        if (resolveContext.log)
                                                resolveContext.log(
                                                        "Field '" +
                                                                this.field +
                                                                "' doesn't contain a valid alias configuration"
                                                );
                                        return callback();
                                }
                                const data1 = fieldData[innerRequest];
                                const data2 = fieldData[innerRequest.replace(/^\.\//, "")];
                                const data = typeof data1 !== "undefined" ? data1 : data2;
                                if (data === innerRequest) return callback();
                                if (data === undefined) return callback();
                                if (data === false) {
                                        /** @type {ResolveRequest} */
                                        const ignoreObj = {
                                                ...request,
                                                path: false
                                        };
                                        return callback(null, ignoreObj);
                                }
                                const obj = {
                                        ...request,
                                        path: request.descriptionFileRoot,
                                        request: data,
                                        fullySpecified: false
                                };
                                resolver.doResolve(
                                        target,
                                        obj,
                                        "aliased from description file " +
                                                request.descriptionFilePath +
                                                " with mapping '" +
                                                innerRequest +
                                                "' to '" +
                                                data +
                                                "'",
                                        resolveContext,
                                        (err, result) => {
                                                if (err) return callback(err);

                                                // Don't allow other aliasing or raw request
                                                if (result === undefined) return callback(null, null);
                                                callback(null, result);
                                        }
                                );
                        });
        }
};