From 7014480409bd04fa3d0e2572d15314d62d731a37 Mon Sep 17 00:00:00 2001
From: "github-actions[bot]"
 <41898282+github-actions[bot]@users.noreply.github.com>
Date: Tue, 30 Jun 2026 01:54:52 +0000
Subject: [PATCH] [ci-fix] De-flake DispatcherTests pooled-thread state leak

BackgroundThreadDoesNotGetDispatcherFromMainThread sets the [ThreadStatic]
DispatcherProviderStubOptions.SkipDispatcherCreation flag inside a Task.Run
delegate that executes on a ThreadPool thread, and never resets it. The
pooled thread is returned to the pool with the flag still true. A later
test whose async continuation resumes on that same pooled thread then gets
a null dispatcher from Dispatcher.GetForCurrentThread(), producing an
intermittent NullReferenceException (observed as green-on-retry flakiness).

Reset the flag in a finally so the pooled thread is always returned clean.
The Assert.Null assertion is preserved unchanged.

Refs: dotnet/maui#36192

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 .../UnitTests/Dispatching/DispatcherTests.cs  | 20 +++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/src/Core/tests/UnitTests/Dispatching/DispatcherTests.cs b/src/Core/tests/UnitTests/Dispatching/DispatcherTests.cs
index 586c962e04f5..6521366e99a4 100644
--- a/src/Core/tests/UnitTests/Dispatching/DispatcherTests.cs
+++ b/src/Core/tests/UnitTests/Dispatching/DispatcherTests.cs
@@ -60,10 +60,22 @@ public Task BackgroundThreadDoesNotGetDispatcherFromMainThread() =>
 
 				await Task.Run(() =>
 				{
-					DispatcherProviderStubOptions.SkipDispatcherCreation = true;
-
-					var dispatcher = Dispatcher.GetForCurrentThread();
-					Assert.Null(dispatcher);
+					// SkipDispatcherCreation is [ThreadStatic] and this delegate runs on a pooled
+					// thread. Reset it in a finally so the thread is returned to the pool clean.
+					// Otherwise the leaked flag makes Dispatcher.GetForCurrentThread() return null
+					// for a later test whose async continuation happens to resume on this same
+					// pooled thread, producing an intermittent NullReferenceException.
+					try
+					{
+						DispatcherProviderStubOptions.SkipDispatcherCreation = true;
+
+						var dispatcher = Dispatcher.GetForCurrentThread();
+						Assert.Null(dispatcher);
+					}
+					finally
+					{
+						DispatcherProviderStubOptions.SkipDispatcherCreation = false;
+					}
 				});
 			});