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fix: race condition between renders, FindComponents, and WaitForHelper
fixes #577. The problem is that FindComponents traverses down the render tree when invoked, and this ensures that no renders happens while it does so, without using locks like previous, which could result in deadlocks. fix: aways wrap FindComponentsInternal in Dispatcher fix: optimize wait for logging fix: ensure failure tasks in WaitForHelper run on Renderer schedular
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9 files changed

+196
-162
lines changed

9 files changed

+196
-162
lines changed

‎CHANGELOG.md‎

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -6,6 +6,10 @@ All notable changes to **bUnit** will be documented in this file. The project ad
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## [Unreleased]
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### Fixes
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- A race condition existed between `WaitForState` / `WaitForAssertion` and `FindComponents`, if the first used the latter. Reported by [@rmihael](https://github.com/rmihael), [@SviatoslavK](https://github.com/SviatoslavK), and [@RaphaelMarcouxCTRL](https://github.com/RaphaelMarcouxCTRL). Fixed by [@egil](https://github.com/egil) and [@linkdotnet](https://github.com/linkdotnet).
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## [1.8.15] - 2022-05-19
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### Added

‎src/bunit.core/Extensions/WaitForHelpers/WaitForHelper.cs‎

Lines changed: 109 additions & 100 deletions
Original file line numberDiff line numberDiff line change
@@ -9,8 +9,6 @@ namespace Bunit.Extensions.WaitForHelpers;
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/// </summary>
1010
public abstract class WaitForHelper<T> : IDisposable
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{
12-
private readonly object lockObject = new();
13-
private readonly Timer timer;
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private readonly TaskCompletionSource<T> checkPassedCompletionSource;
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private readonly Func<(bool CheckPassed, T Content)> completeChecker;
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private readonly IRenderedFragmentBase renderedFragment;
@@ -40,143 +38,154 @@ public abstract class WaitForHelper<T> : IDisposable
4038
/// </summary>
4139
public Task<T> WaitTask { get; }
4240

43-
4441
/// <summary>
4542
/// Initializes a new instance of the <see cref="WaitForHelper{T}"/> class.
4643
/// </summary>
47-
[System.Diagnostics.CodeAnalysis.SuppressMessage("Performance", "CA1849:Call async methods when in an async method", Justification = "Using x.Result inside a ContinueWith is safe.")]
48-
protected WaitForHelper(IRenderedFragmentBase renderedFragment, Func<(bool CheckPassed, T Content)> completeChecker, TimeSpan? timeout = null)
44+
protected WaitForHelper(
45+
IRenderedFragmentBase renderedFragment,
46+
Func<(bool CheckPassed, T Content)> completeChecker,
47+
TimeSpan? timeout = null)
4948
{
5049
this.renderedFragment = renderedFragment ?? throw new ArgumentNullException(nameof(renderedFragment));
5150
this.completeChecker = completeChecker ?? throw new ArgumentNullException(nameof(completeChecker));
51+
5252
logger = renderedFragment.Services.CreateLogger<WaitForHelper<T>>();
53+
checkPassedCompletionSource = new TaskCompletionSource<T>();
54+
WaitTask = CreateWaitTask(renderedFragment, timeout);
5355

54-
var renderer = renderedFragment.Services.GetRequiredService<ITestRenderer>();
55-
var renderException = renderer
56-
.UnhandledException
57-
.ContinueWith(x => Task.FromException<T>(x.Result), CancellationToken.None, TaskContinuationOptions.OnlyOnRanToCompletion, TaskScheduler.Current)
58-
.Unwrap();
56+
InitializeWaiting();
57+
}
5958

60-
checkPassedCompletionSource = new TaskCompletionSource<T>();
61-
WaitTask = Task.WhenAny(checkPassedCompletionSource.Task, renderException).Unwrap();
59+
/// <summary>
60+
/// Disposes the wait helper and cancels the any ongoing waiting, if it is not
61+
/// already in one of the other completed states.
62+
/// </summary>
63+
public void Dispose()
64+
{
65+
Dispose(disposing: true);
66+
GC.SuppressFinalize(this);
67+
}
6268

63-
timer = new Timer(OnTimeout, this, Timeout.InfiniteTimeSpan, Timeout.InfiniteTimeSpan);
69+
/// <summary>
70+
/// Disposes of the wait task and related logic.
71+
/// </summary>
72+
/// <remarks>
73+
/// The disposing parameter should be false when called from a finalizer, and true when called from the
74+
/// <see cref="Dispose()"/> method. In other words, it is true when deterministically called and false when non-deterministically called.
75+
/// </remarks>
76+
/// <param name="disposing">Set to true if called from <see cref="Dispose()"/>, false if called from a finalizer.f.</param>
77+
protected virtual void Dispose(bool disposing)
78+
{
79+
if (isDisposed || !disposing)
80+
return;
81+
82+
isDisposed = true;
83+
checkPassedCompletionSource.TrySetCanceled();
84+
renderedFragment.OnAfterRender -= OnAfterRender;
85+
logger.LogWaiterDisposed(renderedFragment.ComponentId);
86+
}
6487

88+
private void InitializeWaiting()
89+
{
6590
if (!WaitTask.IsCompleted)
6691
{
92+
var renderCountAtSubscribeTime = renderedFragment.RenderCount;
93+
94+
// Before subscribing to renderedFragment.OnAfterRender,
95+
// we need to make sure that the desired state has not already been reached.
6796
OnAfterRender(this, EventArgs.Empty);
68-
this.renderedFragment.OnAfterRender += OnAfterRender;
69-
OnAfterRender(this, EventArgs.Empty);
70-
StartTimer(timeout);
97+
98+
SubscribeToOnAfterRender();
99+
100+
// If the render count from before subscribing has changes
101+
// till now, we need to do trigger another check, since
102+
// the render may have happened asynchronously and before
103+
// the subscription was set up.
104+
if (renderCountAtSubscribeTime < renderedFragment.RenderCount)
105+
{
106+
OnAfterRender(this, EventArgs.Empty);
107+
}
71108
}
72109
}
73110

74-
private void StartTimer(TimeSpan? timeout)
111+
private Task<T> CreateWaitTask(IRenderedFragmentBase renderedFragment, TimeSpan? timeout)
75112
{
76-
if (isDisposed)
77-
return;
113+
var renderer = renderedFragment.Services.GetRequiredService<ITestRenderer>();
78114

79-
lock (lockObject)
115+
// Two to failure conditions, that the renderer captures an unhandled
116+
// exception from a component or itself, or that the timeout is reached,
117+
// are executed on the renderes schedular, to ensure that OnAfterRender
118+
// and the continuations does not happen at the same time.
119+
var failureTask = renderer.Dispatcher.InvokeAsync(() =>
80120
{
81-
if (isDisposed)
82-
return;
83-
84-
timer.Change(GetRuntimeTimeout(timeout), Timeout.InfiniteTimeSpan);
85-
}
121+
var taskScheduler = TaskScheduler.FromCurrentSynchronizationContext();
122+
123+
var renderException = renderer
124+
.UnhandledException
125+
.ContinueWith(
126+
x => Task.FromException<T>(x.Result),
127+
CancellationToken.None,
128+
TaskContinuationOptions.OnlyOnRanToCompletion | TaskContinuationOptions.ExecuteSynchronously,
129+
taskScheduler);
130+
131+
var timeoutTask = Task.Delay(GetRuntimeTimeout(timeout))
132+
.ContinueWith(
133+
x =>
134+
{
135+
logger.LogWaiterTimedOut(renderedFragment.ComponentId);
136+
return Task.FromException<T>(new WaitForFailedException(TimeoutErrorMessage, capturedException));
137+
},
138+
CancellationToken.None,
139+
TaskContinuationOptions.OnlyOnRanToCompletion | TaskContinuationOptions.ExecuteSynchronously,
140+
taskScheduler);
141+
142+
return Task.WhenAny(renderException, timeoutTask).Unwrap();
143+
}).Unwrap();
144+
145+
return Task.WhenAny(failureTask, checkPassedCompletionSource.Task).Unwrap();
86146
}
87147

88148
private void OnAfterRender(object? sender, EventArgs args)
89149
{
90-
if (isDisposed)
150+
if (isDisposed || WaitTask.IsCompleted)
91151
return;
92152

93-
lock (lockObject)
153+
try
94154
{
95-
if (isDisposed)
96-
return;
155+
logger.LogCheckingWaitCondition(renderedFragment.ComponentId);
97156

98-
try
157+
var checkResult = completeChecker();
158+
if (checkResult.CheckPassed)
99159
{
100-
logger.LogCheckingWaitCondition(renderedFragment.ComponentId);
101-
102-
var checkResult = completeChecker();
103-
if (checkResult.CheckPassed)
104-
{
105-
checkPassedCompletionSource.TrySetResult(checkResult.Content);
106-
logger.LogCheckCompleted(renderedFragment.ComponentId);
107-
Dispose();
108-
}
109-
else
110-
{
111-
logger.LogCheckFailed(renderedFragment.ComponentId);
112-
}
160+
checkPassedCompletionSource.TrySetResult(checkResult.Content);
161+
logger.LogCheckCompleted(renderedFragment.ComponentId);
162+
Dispose();
113163
}
114-
catch (Exception ex)
164+
else
115165
{
116-
capturedException = ex;
117-
logger.LogCheckThrow(renderedFragment.ComponentId, ex);
118-
119-
if (StopWaitingOnCheckException)
120-
{
121-
checkPassedCompletionSource.TrySetException(new WaitForFailedException(CheckThrowErrorMessage, capturedException));
122-
Dispose();
123-
}
166+
logger.LogCheckFailed(renderedFragment.ComponentId);
124167
}
125168
}
126-
}
127-
128-
private void OnTimeout(object? state)
129-
{
130-
if (isDisposed)
131-
return;
132-
133-
lock (lockObject)
169+
catch (Exception ex)
134170
{
135-
if (isDisposed)
136-
return;
137-
138-
logger.LogWaiterTimedOut(renderedFragment.ComponentId);
171+
capturedException = ex;
172+
logger.LogCheckThrow(renderedFragment.ComponentId, ex);
139173

140-
checkPassedCompletionSource.TrySetException(new WaitForFailedException(TimeoutErrorMessage, capturedException));
141-
142-
Dispose();
174+
if (StopWaitingOnCheckException)
175+
{
176+
checkPassedCompletionSource.TrySetException(new WaitForFailedException(CheckThrowErrorMessage, capturedException));
177+
Dispose();
178+
}
143179
}
144180
}
145181

146-
/// <summary>
147-
/// Disposes the wait helper and cancels the any ongoing waiting, if it is not
148-
/// already in one of the other completed states.
149-
/// </summary>
150-
public void Dispose()
151-
{
152-
Dispose(disposing: true);
153-
GC.SuppressFinalize(this);
154-
}
155-
156-
/// <summary>
157-
/// Disposes of the wait task and related logic.
158-
/// </summary>
159-
/// <remarks>
160-
/// The disposing parameter should be false when called from a finalizer, and true when called from the
161-
/// <see cref="Dispose()"/> method. In other words, it is true when deterministically called and false when non-deterministically called.
162-
/// </remarks>
163-
/// <param name="disposing">Set to true if called from <see cref="Dispose()"/>, false if called from a finalizer.f.</param>
164-
protected virtual void Dispose(bool disposing)
182+
private void SubscribeToOnAfterRender()
165183
{
166-
if (isDisposed || !disposing)
167-
return;
168-
169-
lock (lockObject)
170-
{
171-
if (isDisposed)
172-
return;
173-
174-
isDisposed = true;
175-
renderedFragment.OnAfterRender -= OnAfterRender;
176-
timer.Dispose();
177-
checkPassedCompletionSource.TrySetCanceled();
178-
logger.LogWaiterDisposed(renderedFragment.ComponentId);
179-
}
184+
// There might not be a need to subscribe if the WaitTask has already
185+
// been completed, perhaps due to an unhandled exception from the
186+
// renderer or from the initial check by the checker.
187+
if (!isDisposed && !WaitTask.IsCompleted)
188+
renderedFragment.OnAfterRender += OnAfterRender;
180189
}
181190

182191
private static TimeSpan GetRuntimeTimeout(TimeSpan? timeout)

‎src/bunit.core/Extensions/WaitForHelpers/WaitForHelperLoggerExtensions.cs‎

Lines changed: 36 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -23,20 +23,50 @@ private static readonly Action<ILogger, int, Exception> CheckThrow
2323
= LoggerMessage.Define<int>(LogLevel.Debug, new EventId(20, "OnTimeout"), "The waiter for component {Id} disposed.");
2424

2525
internal static void LogCheckingWaitCondition<T>(this ILogger<WaitForHelper<T>> logger, int componentId)
26-
=> CheckingWaitCondition(logger, componentId, null);
26+
{
27+
if (logger.IsEnabled(LogLevel.Debug))
28+
{
29+
CheckingWaitCondition(logger, componentId, null);
30+
}
31+
}
2732

2833
internal static void LogCheckCompleted<T>(this ILogger<WaitForHelper<T>> logger, int componentId)
29-
=> CheckCompleted(logger, componentId, null);
34+
{
35+
if (logger.IsEnabled(LogLevel.Debug))
36+
{
37+
CheckCompleted(logger, componentId, null);
38+
}
39+
}
3040

3141
internal static void LogCheckFailed<T>(this ILogger<WaitForHelper<T>> logger, int componentId)
32-
=> CheckFailed(logger, componentId, null);
42+
{
43+
if (logger.IsEnabled(LogLevel.Debug))
44+
{
45+
CheckFailed(logger, componentId, null);
46+
}
47+
}
3348

3449
internal static void LogCheckThrow<T>(this ILogger<WaitForHelper<T>> logger, int componentId, Exception exception)
35-
=> CheckThrow(logger, componentId, exception);
50+
{
51+
if (logger.IsEnabled(LogLevel.Debug))
52+
{
53+
CheckThrow(logger, componentId, exception);
54+
}
55+
}
3656

3757
internal static void LogWaiterTimedOut<T>(this ILogger<WaitForHelper<T>> logger, int componentId)
38-
=> WaiterTimedOut(logger, componentId, null);
58+
{
59+
if (logger.IsEnabled(LogLevel.Debug))
60+
{
61+
WaiterTimedOut(logger, componentId, null);
62+
}
63+
}
3964

4065
internal static void LogWaiterDisposed<T>(this ILogger<WaitForHelper<T>> logger, int componentId)
41-
=> WaiterDisposed(logger, componentId, null);
66+
{
67+
if (logger.IsEnabled(LogLevel.Debug))
68+
{
69+
WaiterDisposed(logger, componentId, null);
70+
}
71+
}
4272
}

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