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[Blazor] Throw meaningful JSTimeoutException for JSRuntime calls that timeout #62539

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[Blazor] Throw meaningful JSTimeoutException for JSRuntime calls that timeout #62539

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e8c7fb3
Initial plan
Copilot Jul 2, 2025
941f88e
Implement JSTimeoutException and timeout handling in ComponentBase
Copilot Jul 2, 2025
169cab9
Replace JSTimeoutException with TimeoutException per feedback
Copilot Jul 2, 2025
0a75d59
Add test for cancellation token taking precedence over timeout
Copilot Jul 2, 2025
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13 changes: 11 additions & 2 deletions src/JSInterop/Microsoft.JSInterop/src/JSRuntime.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -113,8 +113,17 @@ public ValueTask<IJSObjectReference> InvokeNewAsync(string identifier, Cancellat
if (DefaultAsyncTimeout.HasValue)
{
using var cts = new CancellationTokenSource(DefaultAsyncTimeout.Value);
// We need to await here due to the using
return await InvokeAsync<TValue>(targetInstanceId, identifier, callType, cts.Token, args);

try
{
// We need to await here due to the using
return await InvokeAsync<TValue>(targetInstanceId, identifier, callType, cts.Token, args);
}
catch (OperationCanceledException) when (cts.Token.IsCancellationRequested)
{
// This was cancelled due to our timeout, throw a more meaningful exception
throw new TimeoutException("A JavaScript interop call timed out. Consider increasing the timeout duration if the operation is expected to take longer.");
}
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@akoeplinger akoeplinger Jul 2, 2025 •
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I think we should do the exception check in ComponentBase.cs like Safia mentioned in #21384 (comment)

The current code won't work if you e.g. pass in your own CancellationToken instead of setting DefaultAsyncTimeout.

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That would be already a bigger change, with adding CancellationTokenSource parameter to public async methods like OnInitializedAsync. I did not see that when I was assigning copilot. In this case, that's not a fast fix. Let's keep it in the backlog.

}

return await InvokeAsync<TValue>(targetInstanceId, identifier, callType, CancellationToken.None, args);
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22 changes: 20 additions & 2 deletions src/JSInterop/Microsoft.JSInterop/test/JSRuntimeTest.cs
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Expand Up @@ -37,7 +37,7 @@ public void DispatchesAsyncCallsWithDistinctAsyncHandles()
}

[Fact]
public async Task InvokeAsync_CancelsAsyncTask_AfterDefaultTimeout()
public async Task InvokeAsync_ThrowsTimeoutException_AfterDefaultTimeout()
{
// Arrange
var runtime = new TestJSRuntime();
Expand All @@ -47,7 +47,7 @@ public async Task InvokeAsync_CancelsAsyncTask_AfterDefaultTimeout()
var task = runtime.InvokeAsync<object>("test identifier 1", "arg1", 123, true);

// Assert
await Assert.ThrowsAsync<TaskCanceledException>(async () => await task);
await Assert.ThrowsAsync<TimeoutException>(async () => await task);
}

[Fact]
Expand Down Expand Up @@ -82,6 +82,24 @@ public async Task InvokeAsync_CancelsAsyncTasksWhenCancellationTokenFires()
await Assert.ThrowsAsync<TaskCanceledException>(async () => await task);
}

[Fact]
public async Task InvokeAsync_CancelsWithTaskCanceledException_WhenCancellationTokenFiresBeforeTimeout()
{
// Arrange
using var cts = new CancellationTokenSource();
var runtime = new TestJSRuntime();
// Set a long timeout, but cancel before it fires
runtime.DefaultTimeout = TimeSpan.FromSeconds(10);

// Act
var task = runtime.InvokeAsync<object>("test identifier 1", cts.Token, new object[] { "arg1", 123, true });

cts.Cancel();

// Assert - Should throw TaskCanceledException, not TimeoutException
await Assert.ThrowsAsync<TaskCanceledException>(async () => await task);
}

[Fact]
public async Task InvokeAsync_DoesNotStartWorkWhenCancellationHasBeenRequested()
{
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