feat(legacy): normalize exports paths

packages/legacy/package.json

@@ -40,6 +40,9 @@
   "peerDependencies": {
     "rollup": "^1.20.0||^2.0.0"
   },
+  "dependencies": {
+    "@rollup/pluginutils": "^4.1.0"
+  },
   "devDependencies": {
     "@rollup/plugin-buble": "^0.21.3",
     "del-cli": "^3.0.1",

packages/legacy/src/index.js

@@ -1,20 +1,23 @@
 import { resolve } from 'path';
 
+import { normalizePath } from '@rollup/pluginutils';
+
 const validName = /^[a-zA-Z_$][a-zA-Z$_0-9]*$/;
 
 export default function legacy(options) {
   const exports = {};
   Object.keys(options).forEach((file) => {
-    exports[resolve(file)] = options[file];
+    exports[normalizePath(resolve(file))] = options[file];
   });
 
   return {
     name: 'legacy',
 
     transform(content, id) {
-      if (id in exports) {
+      const normalizedId = normalizePath(id);
+      if (normalizedId in exports) {
         let code = content;
-        const value = exports[id];
+        const value = exports[normalizedId];
 
         if (typeof value === 'string') {
           // default export

packages/legacy/test/test.js

@@ -1,6 +1,10 @@
+const path = require('path');
+
 const test = require('ava');
 const { rollup } = require('rollup');
 
+const { normalizePath } = require('@rollup/pluginutils');
+
 const { testBundle } = require('../../../util/test');
 
 const legacy = require('..');
@@ -64,3 +68,25 @@ test('adds a unchanged named export', async (t) => {
   t.plan(1);
   await testBundle(t, bundle);
 });
+
+test('normalized paths', async (t) => {
+  const bundle = await rollup({
+    input: 'fixtures/default-export/main.js',
+    plugins: [
+      {
+        name: 'NormalizedPath',
+        resolveId(importee) {
+          if (importee === './answer') {
+            return normalizePath(path.resolve('./fixtures/default-export/answer.js'));
+          }
+          return null;
+        }
+      },
+      legacy({
+        './fixtures/default-export/answer.js': 'answer'
+      })
+    ]
+  });
+  t.plan(1);
+  await testBundle(t, bundle);
+});