/** * @fileoverview Implements the Node.js require.resolve algorithm * @author Nicholas C. Zakas */ "use strict"; //------------------------------------------------------------------------------ // Requirements //------------------------------------------------------------------------------ const Module = require("module"); //------------------------------------------------------------------------------ // Private //------------------------------------------------------------------------------ const DEFAULT_OPTIONS = { /* * module.paths is an array of paths to search for resolving things relative * to this file. Module.globalPaths contains all of the special Node.js * directories that can also be searched for modules. * * Need to check for existence of module.paths because Jest seems not to * include it. See https://github.com/eslint/eslint/issues/5791. */ lookupPaths: module.paths ? module.paths.concat(Module.globalPaths) : Module.globalPaths.concat() }; /** * Resolves modules based on a set of options. */ class ModuleResolver { /** * Resolves modules based on a set of options. * @param {Object} options The options for resolving modules. * @param {string[]} options.lookupPaths An array of paths to include in the * lookup with the highest priority paths coming first. */ constructor(options) { this.options = Object.assign({}, DEFAULT_OPTIONS, options || {}); } /** * Resolves the file location of a given module relative to the configured * lookup paths. * @param {string} name The module name to resolve. * @param {string} extraLookupPath An extra path to look into for the module. * This path is used with the highest priority. * @returns {string} The resolved file path for the module. * @throws {Error} If the module cannot be resolved. */ resolve(name, extraLookupPath) { /* * First, clone the lookup paths so we're not messing things up for * subsequent calls to this function. Then, move the extraLookupPath to the * top of the lookup paths list so it will be searched first. */ const lookupPaths = this.options.lookupPaths.concat(); lookupPaths.unshift(extraLookupPath); /** * Module._findPath is an internal method to Node.js, then one they use to * lookup file paths when require() is called. So, we are hooking into the * exact same logic that Node.js uses. */ const result = Module._findPath(name, lookupPaths); // eslint-disable-line no-underscore-dangle if (!result) { throw new Error(`Cannot find module '${name}'`); } return result; } } //------------------------------------------------------------------------------ // Public API //------------------------------------------------------------------------------ module.exports = ModuleResolver;