169 lines
10 KiB
Markdown
169 lines
10 KiB
Markdown
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# enhanced-resolve
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Offers an async require.resolve function. It's highly configurable.
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## Features
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- plugin system
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- provide a custom filesystem
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- sync and async node.js filesystems included
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## Getting Started
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### Install
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```sh
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# npm
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npm install enhanced-resolve
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# or Yarn
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yarn add enhanced-resolve
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```
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### Resolve
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There is a Node.js API which allows to resolve requests according to the Node.js resolving rules.
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Sync and async APIs are offered. A `create` method allows to create a custom resolve function.
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```js
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const resolve = require("enhanced-resolve");
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resolve("/some/path/to/folder", "module/dir", (err, result) => {
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result; // === "/some/path/node_modules/module/dir/index.js"
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});
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resolve.sync("/some/path/to/folder", "../../dir");
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// === "/some/path/dir/index.js"
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const myResolve = resolve.create({
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// or resolve.create.sync
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extensions: [".ts", ".js"]
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// see more options below
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});
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myResolve("/some/path/to/folder", "ts-module", (err, result) => {
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result; // === "/some/node_modules/ts-module/index.ts"
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});
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```
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### Creating a Resolver
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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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```js
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const fs = require("fs");
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const { CachedInputFileSystem, ResolverFactory } = require("enhanced-resolve");
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// create a resolver
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const myResolver = ResolverFactory.createResolver({
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// Typical usage will consume the `fs` + `CachedInputFileSystem`, which wraps Node.js `fs` to add caching.
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fileSystem: new CachedInputFileSystem(fs, 4000),
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extensions: [".js", ".json"]
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/* any other resolver options here. Options/defaults can be seen below */
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});
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// resolve a file with the new resolver
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const context = {};
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const resolveContext = {};
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const lookupStartPath = "/Users/webpack/some/root/dir";
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const request = "./path/to-look-up.js";
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myResolver.resolve({}, lookupStartPath, request, resolveContext, (
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err /*Error*/,
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filepath /*string*/
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) => {
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// Do something with the path
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});
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```
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#### Resolver Options
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| Field | Default | Description |
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|------------------|-----------------------------| --------------------------------------------------------------------------------------------------------------------------------------------------------- |
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| alias | [] | A list of module alias configurations or an object which maps key to value |
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| aliasFields | [] | A list of alias fields in description files |
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| extensionAlias | {} | An object which maps extension to extension aliases |
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| 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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| cacheWithContext | true | If unsafe cache is enabled, includes `request.context` in the cache key |
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| conditionNames | ["node"] | A list of exports field condition names |
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| descriptionFiles | ["package.json"] | A list of description files to read from |
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| enforceExtension | false | Enforce that a extension from extensions must be used |
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| exportsFields | ["exports"] | A list of exports fields in description files |
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| extensions | [".js", ".json", ".node"] | A list of extensions which should be tried for files |
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| fallback | [] | Same as `alias`, but only used if default resolving fails |
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| fileSystem | | The file system which should be used |
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| 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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| mainFields | ["main"] | A list of main fields in description files |
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| mainFiles | ["index"] | A list of main files in directories |
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| modules | ["node_modules"] | A list of directories to resolve modules from, can be absolute path or folder name |
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| plugins | [] | A list of additional resolve plugins which should be applied |
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| resolver | undefined | A prepared Resolver to which the plugins are attached |
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| resolveToContext | false | Resolve to a context instead of a file |
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| preferRelative | false | Prefer to resolve module requests as relative request and fallback to resolving as module |
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| preferAbsolute | false | Prefer to resolve server-relative urls as absolute paths before falling back to resolve in roots |
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| restrictions | [] | A list of resolve restrictions |
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| roots | [] | A list of root paths |
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| symlinks | true | Whether to resolve symlinks to their symlinked location |
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| unsafeCache | false | Use this cache object to unsafely cache the successful requests |
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## Plugins
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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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These plugins can extend the functionality of the library, adding other ways for files/contexts to be resolved.
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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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### Plugin Boilerplate
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```js
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class MyResolverPlugin {
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constructor(source, target) {
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this.source = source;
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this.target = target;
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}
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apply(resolver) {
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const target = resolver.ensureHook(this.target);
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resolver
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.getHook(this.source)
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.tapAsync("MyResolverPlugin", (request, resolveContext, callback) => {
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// Any logic you need to create a new `request` can go here
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resolver.doResolve(target, request, null, resolveContext, callback);
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});
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}
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}
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```
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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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## Escaping
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It's allowed to escape `#` as `\0#` to avoid parsing it as fragment.
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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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## Tests
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```javascript
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yarn test
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```
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[](http://travis-ci.org/webpack/enhanced-resolve)
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## Passing options from webpack
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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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```
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resolve: {
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extensions: ['.js', '.jsx'],
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modules: [path.resolve(__dirname, 'src'), 'node_modules'],
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plugins: [new DirectoryNamedWebpackPlugin()]
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...
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},
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```
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## License
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Copyright (c) 2012-2019 JS Foundation and other contributors
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MIT (http://www.opensource.org/licenses/mit-license.php)
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