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| # enhanced-resolve | |
| [![npm][npm]][npm-url] | |
| [![Build Status][build-status]][build-status-url] | |
| [![codecov][codecov-badge]][codecov-url] | |
| [![Install Size][size]][size-url] | |
| [![GitHub Discussions][discussion]][discussion-url] | |
| 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 lookupStartPath = "/Users/webpack/some/root/dir"; | |
| const request = "./path/to-look-up.js"; | |
| const resolveContext = {}; | |
| myResolver.resolve(context, 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 | [] | 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 | |
| ``` | |
| ## 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) | |
| [npm]: https://img.shields.io/npm/v/enhanced-resolve.svg | |
| [npm-url]: https://www.npmjs.com/package/enhanced-resolve | |
| [build-status]: https://github.com/webpack/enhanced-resolve/actions/workflows/test.yml/badge.svg?branch=master | |
| [build-status-url]: https://github.com/webpack/enhanced-resolve/actions | |
| [codecov-badge]: https://codecov.io/gh/webpack/enhanced-resolve/branch/main/graph/badge.svg?token=6B6NxtsZc3 | |
| [codecov-url]: https://codecov.io/gh/webpack/enhanced-resolve | |
| [size]: https://packagephobia.com/badge?p=enhanced-resolve | |
| [size-url]: https://packagephobia.com/result?p=enhanced-resolve | |
| [discussion]: https://img.shields.io/github/discussions/webpack/webpack | |
| [discussion-url]: https://github.com/webpack/webpack/discussions | |