feat(node-resolve): dedupe by package name (#99)

BREAKING CHANGE: those depending on the past behavior, in which deep imports are not deduplicated, may experience unexpected results. 

* feat(node-resolve): dedupe by package name

* chore: add comments to package name function

* docs(node-resolve): update dedupe docs

Co-authored-by: Andrew Powell <[email protected]>

Author: LarsDenBakker

packages/node-resolve/README.md

@@ -120,7 +120,21 @@ Default: `[]`
 Force resolving for these modules to root's node_modules that helps to prevent bundling the same package multiple times if package is imported from dependencies.
 
 ```
-dedupe: [ 'react', 'react-dom' ]
+dedupe: [ 'my-package', '@namespace/my-package' ]
+```
+
+This will deduplicate bare imports such as:
+
+```js
+import 'my-package';
+import '@namespace/my-package';
+```
+
+And it will deduplicate deep imports such as:
+
+```js
+import 'my-package/foo.js';
+import '@namespace/my-package/bar.js';
 ```
 
 ### `customResolveOptions`

packages/node-resolve/src/index.js

@@ -136,6 +136,25 @@ function resolveImportSpecifiers(importSpecifierList, resolveOptions) {
   return p;
 }
 
+// returns the imported package name for bare module imports
+function getPackageName(id) {
+  if (id.startsWith('.') || id.startsWith('/')) {
+    return null;
+  }
+
+  const split = id.split('/');
+
+  // @my-scope/my-package/foo.js -> @my-scope/my-package
+  // @my-scope/my-package -> @my-scope/my-package
+  if (split[0][0] === '@') {
+    return `${split[0]}/${split[1]}`;
+  }
+
+  // my-package/foo.js -> my-package
+  // my-package -> my-package
+  return split[0];
+}
+
 export default function nodeResolve(options = {}) {
   const mainFields = getMainFields(options);
   const useBrowserOverrides = mainFields.indexOf('browser') !== -1;
@@ -166,7 +185,9 @@ export default function nodeResolve(options = {}) {
   const idToPackageInfo = new Map();
 
   const shouldDedupe =
-    typeof dedupe === 'function' ? dedupe : (importee) => dedupe.includes(importee);
+    typeof dedupe === 'function'
+      ? dedupe
+      : (importee) => dedupe.includes(importee) || dedupe.includes(getPackageName(importee));
 
   function getCachedPackageInfo(pkg, pkgPath) {
     if (packageInfoCache.has(pkgPath)) {

packages/node-resolve/test/dedupe.js

@@ -23,6 +23,34 @@ test('single module version is bundled if dedupe is set', async (t) => {
   t.snapshot(module.exports);
 });
 
+test('dedupes deep imports by package name if dedupe is set', async (t) => {
+  const bundle = await rollup({
+    input: 'react-app-deep-import.js',
+    plugins: [
+      nodeResolve({
+        dedupe: ['react']
+      })
+    ]
+  });
+  const { module } = await testBundle(t, bundle);
+
+  t.snapshot(module.exports);
+});
+
+test('dedupes scoped deep imports by package name if dedupe is set', async (t) => {
+  const bundle = await rollup({
+    input: 'scoped-deep-import.js',
+    plugins: [
+      nodeResolve({
+        dedupe: ['@scoped/deduped']
+      })
+    ]
+  });
+  const { module } = await testBundle(t, bundle);
+
+  t.snapshot(module.exports);
+});
+
 test('single module version is bundled if dedupe is set as a function', async (t) => {
   const bundle = await rollup({
     input: 'react-app.js',

packages/node-resolve/test/fixtures/node_modules/@scoped/deduped/deep.js

@@ -0,0 +1,4 @@
+import React from 'react/deep.js';
+import ReactConsumer from 'react-consumer/deep.js';
+
+export { React, ReactConsumer };

packages/node-resolve/test/fixtures/node_modules/react-consumer/deep.js

@@ -0,0 +1,4 @@
+import ScopedDeduped from '@scoped/deduped/deep.js';
+import ScopedDedupedConsumer from 'scoped-deduped-consumer';
+
+export { ScopedDeduped, ScopedDedupedConsumer };

packages/node-resolve/test/fixtures/node_modules/react-consumer/node_modules/react/deep.js

@@ -4,6 +4,24 @@ The actual snapshot is saved in `dedupe.js.snap`.
 
 Generated by [AVA](https://ava.li).
 
+## dedupes deep imports by package name if dedupe is set
+
+> Snapshot 1
+
+    {
+      React: 'react/deep.js:root',
+      ReactConsumer: 'react-consumer:react/deep.js:root',
+    }
+
+## dedupes scoped deep imports by package name if dedupe is set
+
+> Snapshot 1
+
+    {
+      ScopedDeduped: 'scoped-deduped:root',
+      ScopedDedupedConsumer: 'scoped-deduped-consumer:scoped-deduped:root',
+    }
+
 ## multiple module versions are bundled if dedupe is not set
 
 > Snapshot 1