Fix duplicate asset references

packages/core/core/src/BundleGraph.js

@@ -1122,6 +1122,11 @@ export default class BundleGraph {
   }
 
   isAssetReferenced(bundle: Bundle, asset: Asset): boolean {
+    // If the asset is available in multiple bundles, it's referenced.
+    if (this.getBundlesWithAsset(asset).length > 1) {
+      return true;
+    }
+
     let assetNodeId = nullthrows(this._graph.getNodeIdByContentKey(asset.id));
 
     if (

packages/core/integration-tests/test/integration/scope-hoisting/es6/multi-entry-duplicates/one.js

@@ -0,0 +1,5 @@
+import { getValue, add } from './shared';
+
+add();
+
+output = import('./two').then(() => getValue());

packages/core/integration-tests/test/integration/scope-hoisting/es6/multi-entry-duplicates/shared.js

@@ -0,0 +1,9 @@
+let counter = 0;
+
+export function getValue() {
+  return counter;
+}
+
+export function add() {
+  counter++;
+}

packages/core/integration-tests/test/integration/scope-hoisting/es6/multi-entry-duplicates/two.js

@@ -0,0 +1,3 @@
+import { getValue, add } from './shared';
+
+add();

packages/core/integration-tests/test/javascript.js

@@ -7472,5 +7472,25 @@ describe('javascript', function () {
       let res = await run(b, null, {require: false});
       assert.equal(res.output, 123);
     });
+
+    it('duplicate assets should share module scope', async function () {
+      let b = await bundle(
+        [
+          path.join(
+            __dirname,
+            '/integration/scope-hoisting/es6/multi-entry-duplicates/one.js',
+          ),
+          path.join(
+            __dirname,
+            '/integration/scope-hoisting/es6/multi-entry-duplicates/two.js',
+          ),
+        ],
+        options,
+      );
+
+      let result = await runBundle(b, b.getBundles()[0], {}, {require: false});
+
+      assert.equal(await result.output, 2);
+    });
   }
 });