fix(node-resolve): allow deduplicating custom module dirs (#101)

Author: LarsDenBakker

packages/node-resolve/src/index.js

@@ -1,5 +1,5 @@
 /* eslint-disable no-param-reassign, no-shadow, no-undefined */
-import { dirname, extname, join, normalize, resolve, sep } from 'path';
+import { dirname, extname, normalize, resolve, sep } from 'path';
 
 import fs, { realpathSync } from 'fs';
 
@@ -296,11 +296,7 @@ export default function nodeResolve(options = {}) {
       // ignore IDs with null character, these belong to other plugins
       if (/\0/.test(importee)) return null;
 
-      const basedir = importer ? dirname(importer) : rootDir;
-
-      if (shouldDedupe(importee)) {
-        importee = join(rootDir, 'node_modules', importee);
-      }
+      const basedir = !importer || shouldDedupe(importee) ? rootDir : dirname(importer);
 
       // https://github.com/defunctzombie/package-browser-field-spec
       const browser = browserMapCache.get(importer);

packages/node-resolve/test/dedupe-custom.js

@@ -0,0 +1,27 @@
+const { join } = require('path');
+
+const test = require('ava');
+const { rollup } = require('rollup');
+
+const { testBundle } = require('../../../util/test');
+
+const nodeResolve = require('..');
+
+process.chdir(join(__dirname, 'fixtures', 'custom-resolve-options'));
+
+test('can deduplicate custom module directory', async (t) => {
+  const bundle = await rollup({
+    input: 'dedupe.js',
+    plugins: [
+      nodeResolve({
+        dedupe: ['package-b'],
+        customResolveOptions: {
+          moduleDirectory: 'js_modules'
+        }
+      })
+    ]
+  });
+  const { module } = await testBundle(t, bundle);
+
+  t.snapshot(module.exports);
+});

packages/node-resolve/test/fixtures/custom-resolve-options/dedupe.js

@@ -0,0 +1,4 @@
+import PackageA from 'package-a';
+import PackageB from 'package-b';
+
+export { PackageA, PackageB };

packages/node-resolve/test/fixtures/custom-resolve-options/js_modules/package-a/index.js

@@ -0,0 +1,3 @@
+import PackageB from 'package-b';
+
+export default `package-a:${PackageB}`;

packages/node-resolve/test/fixtures/custom-resolve-options/js_modules/package-a/js_modules/package-b/index.js

@@ -0,0 +1 @@
+export default 'package-b:nested';

packages/node-resolve/test/fixtures/custom-resolve-options/js_modules/package-b/index.js

@@ -0,0 +1 @@
+export default 'package-b:root';

packages/node-resolve/test/snapshots/dedupe-custom.js.md

@@ -0,0 +1,14 @@
+# Snapshot report for `test/dedupe-custom.js`
+
+The actual snapshot is saved in `dedupe-custom.js.snap`.
+
+Generated by [AVA](https://ava.li).
+
+## can deduplicate custom module directory
+
+> Snapshot 1
+
+    {
+      PackageA: 'package-a:package-b:root',
+      PackageB: 'package-b:root',
+    }