Recursively check reachability when removing asset graphs from bundle…

…s in deduplication (#6004)

packages/core/integration-tests/test/integration/sibling-deduplicate-unreachable/a.js

@@ -0,0 +1,5 @@
+import bar from './intermediate';
+import foo from './intermediate-2';
+import baz from './intermediate-3';
+
+export default baz;

packages/core/integration-tests/test/integration/sibling-deduplicate-unreachable/b.js

@@ -0,0 +1,3 @@
+import bar from './intermediate';
+import barx from './intermediate-2';
+import barz from './intermediate-3';

packages/core/integration-tests/test/integration/sibling-deduplicate-unreachable/c.js

@@ -0,0 +1,2 @@
+import bar from './unreachable';
+import foo from './intermediate-2';

packages/core/integration-tests/test/integration/sibling-deduplicate-unreachable/d.js

@@ -0,0 +1,2 @@
+import baz from './unreachable';
+import bar from './foo';

packages/core/integration-tests/test/integration/sibling-deduplicate-unreachable/foo.js

@@ -0,0 +1,2 @@
+import foo from './unreachable';
+export default 4;

packages/core/integration-tests/test/integration/sibling-deduplicate-unreachable/index.js

@@ -0,0 +1,5 @@
+import('./d');
+import('./c');
+import('./b');
+output = import('./a').then(res => res.default);
+export default output;

packages/core/integration-tests/test/integration/sibling-deduplicate-unreachable/package.json

@@ -0,0 +1,6 @@
+{
+  "@parcel/bundler-default": {
+    "minBundleSize": 200,
+    "maxParallelRequests": 3
+  }
+}

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

@@ -6242,6 +6242,23 @@ describe('javascript', function () {
     assert.deepEqual(o2, ['UIIcon', 'Icon']);
   });
 
+  it('should not deduplicate an asset if it will become unreachable', async function () {
+    let b = await bundle(
+      path.join(
+        __dirname,
+        'integration/sibling-deduplicate-unreachable/index.js',
+      ),
+      {
+        mode: 'production',
+        defaultTargetOptions: {
+          shouldScopeHoist: false,
+        },
+      },
+    );
+    let res = await run(b);
+    assert.equal(await res.default, 'target');
+  });
+
   for (let shouldScopeHoist of [false, true]) {
     let options = {
       defaultTargetOptions: {

packages/core/integration-tests/test/scope-hoisting.js

@@ -5585,5 +5585,17 @@ describe('scope hoisting', function () {
     } finally {
       await workerFarm.end();
     }
+
+    it('should not deduplicate an asset if it will become unreachable', async function () {
+      let b = await bundle(
+        path.join(
+          __dirname,
+          'integration/sibling-deduplicate-unreachable/index.js',
+        ),
+        {mode: 'production'},
+      );
+      let res = await run(b);
+      assert.equal(res, 'target');
+    });
   });
 });