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