From 9607e00d66d87fb9cb0cbe4f5807ba6168232c9d Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 22 Jul 2026 18:37:49 +0000
Subject: [PATCH 1/3] Initial plan


From cd402bc6114b6ebf5573fcc5fdbd43ee068b6636 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 22 Jul 2026 18:51:51 +0000
Subject: [PATCH 2/3] Add regression test for YAML anchor formatting

---
 packages/compose-language-service/bin/docker-compose-langserver | 0
 1 file changed, 0 insertions(+), 0 deletions(-)
 mode change 100644 => 100755 packages/compose-language-service/bin/docker-compose-langserver

diff --git a/packages/compose-language-service/bin/docker-compose-langserver b/packages/compose-language-service/bin/docker-compose-langserver
old mode 100644
new mode 100755

From f505c70bdfd4555881c6a973b5251108cae3e3a7 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 22 Jul 2026 18:52:24 +0000
Subject: [PATCH 3/3] Add regression test for YAML anchor formatting

---
 .../DocumentFormattingProvider.test.ts        | 21 +++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/packages/compose-language-service/src/test/providers/DocumentFormattingProvider.test.ts b/packages/compose-language-service/src/test/providers/DocumentFormattingProvider.test.ts
index fc31fea1..6d7f2d10 100644
--- a/packages/compose-language-service/src/test/providers/DocumentFormattingProvider.test.ts
+++ b/packages/compose-language-service/src/test/providers/DocumentFormattingProvider.test.ts
@@ -65,6 +65,27 @@ volumes:
             await requestDocumentFormattingAndCompare(testConnection, uri, 2, expected2Space);
         });
 
+        it('Should NOT break YAML anchors', async () => {
+            // See https://github.com/microsoft/vscode-containers/issues/537
+            // The anchor must stay inline with its key and not be pushed onto a new line
+            const testObject = `version: "3.5"
+
+x-anchor: &anchor
+  FOO: bar
+
+services:
+  example:
+    <<: *anchor
+    image: alpine
+`;
+
+            const uri = testConnection.sendTextAsYamlDocument(testObject);
+
+            const expected2Space = testObject; // Output will be unchanged, anchors must not be broken
+
+            await requestDocumentFormattingAndCompare(testConnection, uri, 2, expected2Space);
+        });
+
         it('Should NOT wrap long string lines', async () => {
             const testObject = `version: '123'
 services: