# enhanced-resolve Offers an async require.resolve function. It's highly configurable. ## Features - plugin system - provide a custom filesystem - sync and async node.js filesystems included ## Getting Started ### Install ```sh # npm npm install enhanced-resolve # or Yarn yarn add enhanced-resolve ``` ### Resolve There is a Node.js API which allows to resolve requests according to the Node.js resolving rules. Sync and async APIs are offered. A `create` method allows to create a custom resolve function. ```js const resolve = require("enhanced-resolve"); resolve("/some/path/to/folder", "module/dir", (err, result) => { result; // === "/some/path/node_modules/module/dir/index.js" }); resolve.sync("/some/path/to/folder", "../../dir"); // === "/some/path/dir/index.js" const myResolve = resolve.create({ // or resolve.create.sync extensions: [".ts", ".js"] // see more options below }); myResolve("/some/path/to/folder", "ts-module", (err, result) => { result; // === "/some/node_modules/ts-module/index.ts" }); ``` ### Creating a Resolver The easiest way to create a resolver is to use the `createResolver` function on `ResolveFactory`, along with one of the supplied File System implementations. ```js const fs = require("fs"); const { CachedInputFileSystem, ResolverFactory } = require("enhanced-resolve"); // create a resolver const myResolver = ResolverFactory.createResolver({ // Typical usage will consume the `fs` + `CachedInputFileSystem`, which wraps Node.js `fs` to add caching. fileSystem: new CachedInputFileSystem(fs, 4000), extensions: [".js", ".json"] /* any other resolver options here. Options/defaults can be seen below */ }); // resolve a file with the new resolver const context = {}; const resolveContext = {}; const lookupStartPath = "/Users/webpack/some/root/dir"; const request = "./path/to-look-up.js"; myResolver.resolve({}, lookupStartPath, request, resolveContext, ( err /*Error*/, filepath /*string*/ ) => { // Do something with the path }); ``` #### Resolver Options | Field | Default | Description | |------------------|-----------------------------| --------------------------------------------------------------------------------------------------------------------------------------------------------- | | alias | [] | A list of module alias configurations or an object which maps key to value | | aliasFields | [] | A list of alias fields in description files | | extensionAlias | {} | An object which maps extension to extension aliases | | cachePredicate | function() { return true }; | A function which decides whether a request should be cached or not. An object is passed to the function with `path` and `request` properties. | | cacheWithContext | true | If unsafe cache is enabled, includes `request.context` in the cache key | | conditionNames | ["node"] | A list of exports field condition names | | descriptionFiles | ["package.json"] | A list of description files to read from | | enforceExtension | false | Enforce that a extension from extensions must be used | | exportsFields | ["exports"] | A list of exports fields in description files | | extensions | [".js", ".json", ".node"] | A list of extensions which should be tried for files | | fallback | [] | Same as `alias`, but only used if default resolving fails | | fileSystem | | The file system which should be used | | fullySpecified | false | Request passed to resolve is already fully specified and extensions or main files are not resolved for it (they are still resolved for internal requests) | | mainFields | ["main"] | A list of main fields in description files | | mainFiles | ["index"] | A list of main files in directories | | modules | ["node_modules"] | A list of directories to resolve modules from, can be absolute path or folder name | | plugins | [] | A list of additional resolve plugins which should be applied | | resolver | undefined | A prepared Resolver to which the plugins are attached | | resolveToContext | false | Resolve to a context instead of a file | | preferRelative | false | Prefer to resolve module requests as relative request and fallback to resolving as module | | preferAbsolute | false | Prefer to resolve server-relative urls as absolute paths before falling back to resolve in roots | | restrictions | [] | A list of resolve restrictions | | roots | [] | A list of root paths | | symlinks | true | Whether to resolve symlinks to their symlinked location | | unsafeCache | false | Use this cache object to unsafely cache the successful requests | ## Plugins Similar to `webpack`, the core of `enhanced-resolve` functionality is implemented as individual plugins that are executed using [`tapable`](https://github.com/webpack/tapable). These plugins can extend the functionality of the library, adding other ways for files/contexts to be resolved. A plugin should be a `class` (or its ES5 equivalent) with an `apply` method. The `apply` method will receive a `resolver` instance, that can be used to hook in to the event system. ### Plugin Boilerplate ```js class MyResolverPlugin { constructor(source, target) { this.source = source; this.target = target; } apply(resolver) { const target = resolver.ensureHook(this.target); resolver .getHook(this.source) .tapAsync("MyResolverPlugin", (request, resolveContext, callback) => { // Any logic you need to create a new `request` can go here resolver.doResolve(target, request, null, resolveContext, callback); }); } } ``` Plugins are executed in a pipeline, and register which event they should be executed before/after. In the example above, `source` is the name of the event that starts the pipeline, and `target` is what event this plugin should fire, which is what continues the execution of the pipeline. For an example of how these different plugin events create a chain, see `lib/ResolverFactory.js`, in the `//// pipeline ////` section. ## Escaping It's allowed to escape `#` as `\0#` to avoid parsing it as fragment. enhanced-resolve will try to resolve requests containing `#` as path and as fragment, so it will automatically figure out if `./some#thing` means `.../some.js#thing` or `.../some#thing.js`. When a `#` is resolved as path it will be escaped in the result. Here: `.../some\0#thing.js`. ## Tests ```javascript yarn test ``` [![Build Status](https://secure.travis-ci.org/webpack/enhanced-resolve.png?branch=main)](http://travis-ci.org/webpack/enhanced-resolve) ## Passing options from webpack If you are using `webpack`, and you want to pass custom options to `enhanced-resolve`, the options are passed from the `resolve` key of your webpack configuration e.g.: ``` resolve: { extensions: ['.js', '.jsx'], modules: [path.resolve(__dirname, 'src'), 'node_modules'], plugins: [new DirectoryNamedWebpackPlugin()] ... }, ``` ## License Copyright (c) 2012-2019 JS Foundation and other contributors MIT (http://www.opensource.org/licenses/mit-license.php)