126 lines
6.3 KiB
Markdown
126 lines
6.3 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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### 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 {
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NodeJsInputFileSystem,
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CachedInputFileSystem,
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ResolverFactory
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} = 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 `NodeJsInputFileSystem` + `CachedInputFileSystem`, which wraps the Node.js `fs` wrapper to add resilience + caching.
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fileSystem: new CachedInputFileSystem(new NodeJsInputFileSystem(), 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, (err/*Error*/, filepath/*string*/) => {
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// Do something with the path
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});
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```
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For more examples creating different types resolvers (sync/async, context, etc) see `lib/node.js`.
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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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| cacheWithContext | true | If unsafe cache is enabled, includes `request.context` in the cache key |
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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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| enforceModuleExtension | false | Enforce that a extension from moduleExtensions must be used |
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| extensions | [".js", ".json", ".node"] | A list of extensions which should be tried for files |
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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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| roots | [] | A list of directories to resolve request starting with `/` from |
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| ignoreRootsErrors | false | Ignore fatal errors happening during handling of `roots` (allows to add `roots` without a breaking change) |
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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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| unsafeCache | false | Use this cache object to unsafely cache the successful requests |
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| plugins | [] | A list of additional resolve plugins which should be applied |
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| symlinks | true | Whether to resolve symlinks to their symlinked location |
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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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| moduleExtensions | [] | A list of module extensions which should be tried for modules |
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| resolveToContext | false | Resolve to a context instead of a file |
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| restrictions | [] | A list of resolve restrictions |
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| fileSystem | | The file system which should be used |
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| resolver | undefined | A prepared Resolver to which the plugins are attached |
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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). 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.getHook(this.source).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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## Tests
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``` javascript
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npm 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: ['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) 2012-2016 Tobias Koppers
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MIT (http://www.opensource.org/licenses/mit-license.php)
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