| 1 | # enhanced-resolve
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| 2 |
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| 3 | Offers an async require.resolve function. It's highly configurable.
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| 4 |
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| 5 | ## Features
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| 6 |
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| 7 | - plugin system
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| 8 | - provide a custom filesystem
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| 9 | - sync and async node.js filesystems included
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| 10 |
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| 11 | ## Getting Started
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| 12 |
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| 13 | ### Install
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| 14 |
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| 15 | ```sh
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| 16 | # npm
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| 17 | npm install enhanced-resolve
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| 18 | # or Yarn
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| 19 | yarn add enhanced-resolve
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| 20 | ```
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| 21 |
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| 22 | ### Resolve
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| 23 |
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| 24 | There is a Node.js API which allows to resolve requests according to the Node.js resolving rules.
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| 25 | Sync and async APIs are offered. A `create` method allows to create a custom resolve function.
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| 26 |
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| 27 | ```js
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| 28 | const resolve = require("enhanced-resolve");
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| 29 |
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| 30 | resolve("/some/path/to/folder", "module/dir", (err, result) => {
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| 31 | result; // === "/some/path/node_modules/module/dir/index.js"
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| 32 | });
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| 33 |
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| 34 | resolve.sync("/some/path/to/folder", "../../dir");
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| 35 | // === "/some/path/dir/index.js"
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| 36 |
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| 37 | const myResolve = resolve.create({
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| 38 | // or resolve.create.sync
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| 39 | extensions: [".ts", ".js"]
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| 40 | // see more options below
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| 41 | });
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| 42 |
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| 43 | myResolve("/some/path/to/folder", "ts-module", (err, result) => {
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| 44 | result; // === "/some/node_modules/ts-module/index.ts"
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| 45 | });
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| 46 | ```
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| 47 |
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| 48 | ### Creating a Resolver
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| 49 |
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| 50 | The easiest way to create a resolver is to use the `createResolver` function on `ResolveFactory`, along with one of the supplied File System implementations.
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| 51 |
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| 52 | ```js
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| 53 | const fs = require("fs");
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| 54 | const { CachedInputFileSystem, ResolverFactory } = require("enhanced-resolve");
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| 55 |
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| 56 | // create a resolver
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| 57 | const myResolver = ResolverFactory.createResolver({
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| 58 | // Typical usage will consume the `fs` + `CachedInputFileSystem`, which wraps Node.js `fs` to add caching.
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| 59 | fileSystem: new CachedInputFileSystem(fs, 4000),
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| 60 | extensions: [".js", ".json"]
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| 61 | /* any other resolver options here. Options/defaults can be seen below */
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| 62 | });
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| 63 |
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| 64 | // resolve a file with the new resolver
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| 65 | const context = {};
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| 66 | const resolveContext = {};
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| 67 | const lookupStartPath = "/Users/webpack/some/root/dir";
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| 68 | const request = "./path/to-look-up.js";
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| 69 | myResolver.resolve({}, lookupStartPath, request, resolveContext, (
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| 70 | err /*Error*/,
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| 71 | filepath /*string*/
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| 72 | ) => {
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| 73 | // Do something with the path
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| 74 | });
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| 75 | ```
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| 76 |
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| 77 | #### Resolver Options
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| 78 |
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| 79 | | Field | Default | Description |
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| 80 | | ---------------- | --------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------- |
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| 81 | | alias | [] | A list of module alias configurations or an object which maps key to value |
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| 82 | | aliasFields | [] | A list of alias fields in description files |
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| 83 | | 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. |
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| 84 | | cacheWithContext | true | If unsafe cache is enabled, includes `request.context` in the cache key |
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| 85 | | conditionNames | ["node"] | A list of exports field condition names |
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| 86 | | descriptionFiles | ["package.json"] | A list of description files to read from |
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| 87 | | enforceExtension | false | Enforce that a extension from extensions must be used |
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| 88 | | exportsFields | ["exports"] | A list of exports fields in description files |
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| 89 | | extensions | [".js", ".json", ".node"] | A list of extensions which should be tried for files |
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| 90 | | fileSystem | | The file system which should be used |
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| 91 | | 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) |
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| 92 | | mainFields | ["main"] | A list of main fields in description files |
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| 93 | | mainFiles | ["index"] | A list of main files in directories |
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| 94 | | modules | ["node_modules"] | A list of directories to resolve modules from, can be absolute path or folder name |
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| 95 | | plugins | [] | A list of additional resolve plugins which should be applied |
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| 96 | | resolver | undefined | A prepared Resolver to which the plugins are attached |
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| 97 | | resolveToContext | false | Resolve to a context instead of a file |
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| 98 | | preferRelative | false | Prefer to resolve module requests as relative request and fallback to resolving as module |
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| 99 | | preferAbsolute | false | Prefer to resolve server-relative urls as absolute paths before falling back to resolve in roots |
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| 100 | | restrictions | [] | A list of resolve restrictions |
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| 101 | | roots | [] | A list of root paths |
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| 102 | | symlinks | true | Whether to resolve symlinks to their symlinked location |
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| 103 | | unsafeCache | false | Use this cache object to unsafely cache the successful requests |
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| 104 |
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| 105 | ## Plugins
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| 106 |
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| 107 | Similar to `webpack`, the core of `enhanced-resolve` functionality is implemented as individual plugins that are executed using [`tapable`](https://github.com/webpack/tapable).
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| 108 | These plugins can extend the functionality of the library, adding other ways for files/contexts to be resolved.
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| 109 |
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| 110 | 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.
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| 111 |
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| 112 | ### Plugin Boilerplate
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| 113 |
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| 114 | ```js
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| 115 | class MyResolverPlugin {
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| 116 | constructor(source, target) {
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| 117 | this.source = source;
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| 118 | this.target = target;
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| 119 | }
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| 120 |
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| 121 | apply(resolver) {
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| 122 | const target = resolver.ensureHook(this.target);
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| 123 | resolver
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| 124 | .getHook(this.source)
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| 125 | .tapAsync("MyResolverPlugin", (request, resolveContext, callback) => {
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| 126 | // Any logic you need to create a new `request` can go here
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| 127 | resolver.doResolve(target, request, null, resolveContext, callback);
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| 128 | });
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| 129 | }
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| 130 | }
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| 131 | ```
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| 132 |
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| 133 | 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.
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| 134 |
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| 135 | ## Escaping
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| 136 |
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| 137 | It's allowed to escape `#` as `\0#` to avoid parsing it as fragment.
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| 138 |
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| 139 | 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`.
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| 140 |
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| 141 | ## Tests
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| 142 |
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| 143 | ```javascript
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| 144 | npm test
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| 145 | ```
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| 146 |
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| 147 | [](http://travis-ci.org/webpack/enhanced-resolve)
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| 148 |
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| 149 | ## Passing options from webpack
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| 150 |
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| 151 | 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.:
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| 152 |
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| 153 | ```
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| 154 | resolve: {
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| 155 | extensions: ['.js', '.jsx'],
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| 156 | modules: [path.resolve(__dirname, 'src'), 'node_modules'],
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| 157 | plugins: [new DirectoryNamedWebpackPlugin()]
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| 158 | ...
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| 159 | },
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| 160 | ```
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| 161 |
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| 162 | ## License
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| 163 |
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| 164 | Copyright (c) 2012-2019 JS Foundation and other contributors
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| 165 |
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| 166 | MIT (http://www.opensource.org/licenses/mit-license.php)
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