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[ci-fix-net11] De-flake flaky DispatcherTests by resetting leaked ThreadStatic dispatcher flag #36221

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Merged
kubaflo merged 1 commit into from
Jul 27, 2026
Merged

[ci-fix-net11] De-flake flaky DispatcherTests by resetting leaked ThreadStatic dispatcher flag #36221

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20 changes: 16 additions & 4 deletions src/Core/tests/UnitTests/Dispatching/DispatcherTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -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();
Comment on lines +68 to +72
Assert.Null(dispatcher);
}
finally
{
DispatcherProviderStubOptions.SkipDispatcherCreation = false;

@MauiBot MauiBot Jul 7, 2026

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🔍 AI-Generated Review (multi-model)

[major] Logic and Correctness — Resetting only the [ThreadStatic] flag does not undo the DispatcherProviderStub value created while skip mode was enabled. DispatcherProviderStub stores GetForCurrentThread() in a ThreadLocal<IDispatcher?>; when line 72 runs with SkipDispatcherCreation = true, that ThreadLocal caches null for this provider/thread, so a later Dispatcher.GetForCurrentThread() on the same pooled thread can still return the cached null after this finally block. Please avoid caching null in the provider when skip mode is active (or otherwise clear the per-thread cached value) so the dispatcher state is actually restored.

}
});
});

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