source: imaps-frontend/node_modules/enhanced-resolve/lib/ModulesInHierarchicalDirectoriesPlugin.js

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

"use strict";

const forEachBail = require("./forEachBail");
const getPaths = require("./getPaths");

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

module.exports = class ModulesInHierarchicalDirectoriesPlugin {
        /**
         * @param {string | ResolveStepHook} source source
         * @param {string | Array<string>} directories directories
         * @param {string | ResolveStepHook} target target
         */
        constructor(source, directories, target) {
                this.source = source;
                this.directories = /** @type {Array<string>} */ ([]).concat(directories);
                this.target = target;
        }

        /**
         * @param {Resolver} resolver the resolver
         * @returns {void}
         */
        apply(resolver) {
                const target = resolver.ensureHook(this.target);
                resolver
                        .getHook(this.source)
                        .tapAsync(
                                "ModulesInHierarchicalDirectoriesPlugin",
                                (request, resolveContext, callback) => {
                                        const fs = resolver.fileSystem;
                                        const addrs = getPaths(/** @type {string} */ (request.path))
                                                .paths.map(p => {
                                                        return this.directories.map(d => resolver.join(p, d));
                                                })
                                                .reduce((array, p) => {
                                                        array.push.apply(array, p);
                                                        return array;
                                                }, []);
                                        forEachBail(
                                                addrs,
                                                /**
                                                 * @param {string} addr addr
                                                 * @param {(err?: null|Error, result?: null|ResolveRequest) => void} callback callback
                                                 * @returns {void}
                                                 */
                                                (addr, callback) => {
                                                        fs.stat(addr, (err, stat) => {
                                                                if (!err && stat && stat.isDirectory()) {
                                                                        /** @type {ResolveRequest} */
                                                                        const obj = {
                                                                                ...request,
                                                                                path: addr,
                                                                                request: "./" + request.request,
                                                                                module: false
                                                                        };
                                                                        const message = "looking for modules in " + addr;
                                                                        return resolver.doResolve(
                                                                                target,
                                                                                obj,
                                                                                message,
                                                                                resolveContext,
                                                                                callback
                                                                        );
                                                                }
                                                                if (resolveContext.log)
                                                                        resolveContext.log(
                                                                                addr + " doesn't exist or is not a directory"
                                                                        );
                                                                if (resolveContext.missingDependencies)
                                                                        resolveContext.missingDependencies.add(addr);
                                                                return callback();
                                                        });
                                                },
                                                callback
                                        );
                                }
                        );
        }
};