feat(alias): customResolver instead of built-in resolving algorithm (#21

)

* ignore Intellij IDEA dir

* updated pnpm-lock.yaml

According to pnpm actual version and included packages

* @rollup/plugin-alias: customResolver option

Allow to use customResolver instead of built-in resolving algorithm in

* @rollup/plugin-alias: updated readme

customResolver option

* (alias) updated README

customResolver description

* docs: rework custom resolver options and section

.gitignore

@@ -8,3 +8,4 @@ output/
 .eslintcache
 coverage.lcov
 pnpm-debug.log
+.idea

packages/alias/README.md

@@ -60,6 +60,13 @@ Then call `rollup` either via the [CLI](https://www.rollupjs.org/guide/en/#comma
 
 ## Options
 
+### `customResolver`
+
+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).
+
 ### `entries`
 
 Type: `Object | Array[Object]`<br>
@@ -122,6 +129,44 @@ 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 `.wasm`.
 
+## Custom Resolvers
+
+The `customResolver` option can be leveraged to provide separate module resolution for an invidudual alias.
+
+Example:
+```javascript
+// rollup.config.js
+import alias from "@rollup/plugin-alias";
+import resolve from "rollup-plugin-node-resolve";
+
+const customResolver = resolve({
+  extensions: [".mjs", ".js", ".jsx", ".json", ".sass", ".scss"]
+});
+const projectRootDir = path.resolve(__dirname);
+
+export default {
+  // ...
+  plugins: [
+    alias(
+      {
+        entries: [
+          {
+            find: "src",
+            replacement: path.resolve(projectRootDir, "src")
+            // OR place `customResolver` here. See explanation below.
+          }
+        ],
+        customResolver
+      }
+    ),
+    resolve()
+  ]
+};
+```
+
+In the example above the alias `src` is used, which uses the `node-resolve` algorithm for files _aliased_ with `src`, by passing the `customResolver` option. The `resolve()` plugin is kept separate in the plugins list for other files which are not _aliased_ with `src`. The `customResolver` option can be passed inside each `entries` item for granular control over resolving allowing each alias a preferred resolver.
+
+
 ## Meta
 
 [CONTRIBUTING](/.github/CONTRIBUTING.md)

packages/alias/src/index.js

@@ -78,6 +78,27 @@ export default function alias(options = {}) {
 
       let updatedId = normalizeId(importeeId.replace(matchedEntry.find, matchedEntry.replacement));
 
+      let customResolver = null;
+      if (typeof matchedEntry.customResolver === 'function') {
+        customResolver = matchedEntry.customResolver;
+      } else if (
+        typeof matchedEntry.customResolver === 'object' &&
+        typeof matchedEntry.customResolver.resolveId === 'function'
+      ) {
+        customResolver = options.customResolver.resolveId;
+      } else if (typeof options.customResolver === 'function') {
+        customResolver = options.customResolver;
+      } else if (
+        typeof options.customResolver === 'object' &&
+        typeof options.customResolver.resolveId === 'function'
+      ) {
+        customResolver = options.customResolver.resolveId;
+      }
+
+      if (customResolver) {
+        return customResolver(updatedId, importerId);
+      }
+
       if (isFilePath(updatedId)) {
         const directory = posix.dirname(importerId);
 

packages/alias/test/test.js

@@ -272,3 +272,41 @@ test('Works in rollup', (t) =>
           )
         );
     }));
+
+test('Global customResolver function', (t) => {
+  const customResult = 'customResult';
+  const result = alias({
+    entries: [
+      {
+        find: 'test',
+        replacement: path.resolve('./test/files/folder/hipster.jsx')
+      }
+    ],
+    resolve: ['.js', '.jsx'],
+    customResolver: () => customResult
+  });
+
+  const resolved = result.resolveId('test', posix.resolve(DIRNAME, './files/index.js'));
+
+  t.is(resolved, customResult);
+});
+
+test('Local customResolver function', (t) => {
+  const customResult = 'customResult';
+  const localCustomResult = 'localCustomResult';
+  const result = alias({
+    entries: [
+      {
+        find: 'test',
+        replacement: path.resolve('./test/files/folder/hipster.jsx'),
+        customResolver: () => localCustomResult
+      }
+    ],
+    resolve: ['.js', '.jsx'],
+    customResolver: () => customResult
+  });
+
+  const resolved = result.resolveId('test', posix.resolve(DIRNAME, './files/index.js'));
+
+  t.is(resolved, localCustomResult);
+});