From 4ce0a9b9b5ede353b15366088b02c28602baf070 Mon Sep 17 00:00:00 2001
From: Agnieszka Gawrys <agawrys@atlassian.com>
Date: Mon, 22 Aug 2022 14:42:25 -0400
Subject: [PATCH 1/2] consider sibling for parallel availability fix

---
 .../experimental/src/ExperimentalBundler.js   |  1 +
 packages/core/integration-tests/test/html.js  | 24 +++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/packages/bundlers/experimental/src/ExperimentalBundler.js b/packages/bundlers/experimental/src/ExperimentalBundler.js
index da18a9018ad..a5f8d26b012 100644
--- a/packages/bundlers/experimental/src/ExperimentalBundler.js
+++ b/packages/bundlers/experimental/src/ExperimentalBundler.js
@@ -816,6 +816,7 @@ function createIdealGraph(
           parallelAvailability,
           assetsFromBundleRoot,
         );
+        parallelAvailability.add(child); //The next sibling should have older sibling available via parallel
       }
     }
   }
diff --git a/packages/core/integration-tests/test/html.js b/packages/core/integration-tests/test/html.js
index f4bb022b218..724630720cc 100644
--- a/packages/core/integration-tests/test/html.js
+++ b/packages/core/integration-tests/test/html.js
@@ -2809,6 +2809,30 @@ describe('html', function () {
     });
   });
 
+  it('should insert the prelude for sibling bundles referenced in HTML', async function () {
+    let b = await bundle(
+      path.join(
+        __dirname,
+        'integration/scope-hoisting/es6/sibling-dependencies/index.html',
+      ),
+    );
+    assertBundles(b, [
+      {
+        name: 'index.html',
+        assets: ['index.html'],
+      },
+      {
+        assets: ['a.js', 'esmodule-helpers.js'],
+      },
+      {
+        assets: ['b.js'],
+      },
+    ]);
+
+    let res = await run(b, {output: null}, {require: false});
+    assert.equal(res.output, 'a');
+  });
+
   it('should escape quotes in inline style attributes and style tags', async function () {
     let b = await bundle(
       path.join(__dirname, 'integration/html-inline-escape/style.html'),

From d66a974316305a97f8f72b781b63c45a0e2b33e5 Mon Sep 17 00:00:00 2001
From: Agnieszka Gawrys <agawrys@atlassian.com>
Date: Tue, 23 Aug 2022 14:32:18 -0400
Subject: [PATCH 2/2] Add test

---
 packages/core/integration-tests/test/html.js | 22 +++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/packages/core/integration-tests/test/html.js b/packages/core/integration-tests/test/html.js
index 724630720cc..ca014eb2d96 100644
--- a/packages/core/integration-tests/test/html.js
+++ b/packages/core/integration-tests/test/html.js
@@ -2809,7 +2809,10 @@ describe('html', function () {
     });
   });
 
-  it('should insert the prelude for sibling bundles referenced in HTML', async function () {
+  it('should share older JS sibling (script) assets to younger siblings', async function () {
+    // JS script tags are siblings to a common parent, and are marked as such by parallel dependency priority
+    // Becuase of load order any older sibling (and it's assets) are loaded before any subsequent sibling
+    // Which means no younger sibling should have to reference sibling bundles for assets in them
     let b = await bundle(
       path.join(
         __dirname,
@@ -2829,6 +2832,23 @@ describe('html', function () {
       },
     ]);
 
+    let youngerSibling; // bundle containing younger sibling, b.js
+    let olderSibling; // bundle containing old sibling, a.js
+    b.traverseBundles(bundle => {
+      bundle.traverseAssets(asset => {
+        if (asset.filePath.includes('b.js')) {
+          youngerSibling = bundle;
+        } else if (asset.filePath.includes('a.js')) {
+          olderSibling = bundle;
+        }
+      });
+    });
+
+    assert(
+      b.getReferencedBundles(youngerSibling).filter(b => b == olderSibling)
+        .length == 0,
+    );
+
     let res = await run(b, {output: null}, {require: false});
     assert.equal(res.output, 'a');
   });