(alias) Breaking feature: built-in resolving algorithm is replaced in favor of Rollup's this.resolve()

packages/alias/README.md

@@ -37,6 +37,8 @@ Using npm:
 
 ```console
 npm install @rollup/plugin-alias --save-dev
+# or
+yarn add -D @rollup/plugin-alias
 ```
 
 ## Usage
@@ -52,7 +54,7 @@ module.exports = {
     dir: 'output',
     format: 'cjs'
   },
-  plugins: [alias({ resolve: ['.jsx', '.js'] })]
+  plugins: [alias()]
 };
 ```
 
@@ -65,7 +67,7 @@ Then call `rollup` either via the [CLI](https://www.rollupjs.org/guide/en/#comma
 Type: `Function | Object`<br>
 Default: `null`
 
-Instructs the plugin to use an alternative resolving algorithm, rather than the built-in resolver. Please refer to the [Rollup documentation](https://rollupjs.org/guide/en/#hooks) for more information about the `resolveId` hook. For a detailed example, see: [Custom Resolvers](#custom-resolvers).
+Instructs the plugin to use an alternative resolving algorithm, rather than the Rollup's resolver. Please refer to the [Rollup documentation](https://rollupjs.org/guide/en/#hooks) for more information about the `resolveId` hook. For a detailed example, see: [Custom Resolvers](#custom-resolvers).
 
 ### `entries`
 
@@ -98,17 +100,6 @@ entries: [
 ];
 ```
 
-### `resolve`
-
-Type: `Array[String]`<br>
-Default: `['.js']`
-
-Specifies an array of file extensions to use when attempting to resolve an `import` (or `require`). The extensions will be tried in the order they are specified. By default, this option is configured to resolve only files that have the `.js` extension. For example; to resolve both `JSX` and `JS` files:
-
-```js
-alias({ resolve: ['.jsx', '.js'] });
-```
-
 ## Regular Expression Aliases
 
 Regular Expressions can be used to search in a more distinct and complex manner. e.g. To perform partial replacements via sub-pattern matching.
@@ -129,9 +120,13 @@ To replace extensions with another, a pattern like the following might be used:
 
 This would replace the file extension for all imports ending with `.js` to `.alias`.
 
+## Resolving algorithm
+
+This plugin uses resolver plugins specified for Rollup and eventually Rollup default algorithm. If you rely on Node specific features, you probably want [rollup-plugin-node-resolve](https://www.npmjs.com/package/rollup-plugin-node-resolve) in your setup.
+
 ## Custom Resolvers
 
-The `customResolver` option can be leveraged to provide separate module resolution for an invidudual alias.
+The `customResolver` option can be leveraged to provide separate module resolution for an individual alias.
 
 Example:
 

packages/alias/src/index.js

@@ -1,6 +1,4 @@
-import fs from 'fs';
 import { platform } from 'os';
-import path, { posix } from 'path';
 
 import slash from 'slash';
 
@@ -23,15 +21,6 @@ const matches = (pattern, importee) => {
   const importeeHasSlashAfterKey = importee.substring(pattern.length)[0] === '/';
   return importeeStartsWithKey && importeeHasSlashAfterKey;
 };
-const endsWith = (needle, haystack) => haystack.slice(-needle.length) === needle;
-const isFilePath = (id) => /^\.?\//.test(id);
-const exists = (uri) => {
-  try {
-    return fs.statSync(uri).isFile();
-  } catch (e) {
-    return false;
-  }
-};
 
 const normalizeId = (id) => {
   if ((IS_WINDOWS && typeof id === 'string') || VOLUME.test(id)) {
@@ -55,7 +44,6 @@ const getEntries = ({ entries }) => {
 };
 
 export default function alias(options = {}) {
-  const resolve = Array.isArray(options.resolve) ? options.resolve : ['.js'];
   const entries = getEntries(options);
 
   // No aliases?
@@ -77,7 +65,9 @@ export default function alias(options = {}) {
         return null;
       }
 
-      let updatedId = normalizeId(importeeId.replace(matchedEntry.find, matchedEntry.replacement));
+      const updatedId = normalizeId(
+        importeeId.replace(matchedEntry.find, matchedEntry.replacement)
+      );
 
       let customResolver = null;
       if (typeof matchedEntry.customResolver === 'function') {
@@ -100,39 +90,14 @@ export default function alias(options = {}) {
         return customResolver(updatedId, importerId);
       }
 
-      if (isFilePath(updatedId)) {
-        const directory = posix.dirname(importerId);
-
-        // Resolve file names
-        const filePath = posix.resolve(directory, updatedId);
-        const match = resolve
-          .map((ext) => (endsWith(ext, filePath) ? filePath : `${filePath}${ext}`))
-          .find(exists);
-
-        if (match) {
-          updatedId = match;
-          // To keep the previous behaviour we simply return the file path
-          // with extension
-        } else if (endsWith('.js', filePath)) {
-          updatedId = filePath;
-        } else {
-          const indexFilePath = posix.resolve(directory, `${updatedId}/index`);
-          const defaultMatch = resolve.map((ext) => `${indexFilePath}${ext}`).find(exists);
-          if (defaultMatch) {
-            updatedId = defaultMatch;
-          } else {
-            updatedId = `${filePath}.js`;
-          }
+      return this.resolve(updatedId, importer, { skipSelf: true }).then((resolved) => {
+        let finalResult = resolved;
+        if (!finalResult) {
+          finalResult = { id: updatedId };
         }
-      }
 
-      // if alias is windows absoulate path return resolved path or
-      // rollup on windows will throw:
-      //  [TypeError: Cannot read property 'specifier' of undefined]
-      if (VOLUME.test(matchedEntry.replacement)) {
-        return path.resolve(updatedId);
-      }
-      return updatedId;
+        return finalResult;
+      });
     }
   };
 }