[wasm][browser] BrowserHttpHandler_StreamingRequest_Http1Fails throws TaskCanceledException instead of HttpRequestException

[radekdoulik]

Description

System.Net.Http.Functional.Tests.SocketsHttpHandler_ResponseStreamTest.BrowserHttpHandler_StreamingRequest_Http1Fails (source: src/libraries/Common/tests/System/Net/Http/ResponseStreamTest.cs) fails on Browser + CoreCLR (wasm) but passes on Browser + Mono (wasm).

The test sends a streaming (WebAssemblyEnableStreamingRequest) POST over HTTP/1 and expects the browser fetch to reject it quickly:

HttpRequestException ex = await Assert.ThrowsAsync<HttpRequestException>(() => client.SendAsync(req));
Assert.Equal("TypeError: Failed to fetch", ex.Message);

On CoreCLR-wasm the request instead hangs and is canceled by the 100s HttpClient.Timeout:

Assert.Throws() Failure: Exception type was not an exact match
Expected: typeof(System.Net.Http.HttpRequestException)
Actual:   typeof(System.Threading.Tasks.TaskCanceledException)
---- System.Threading.Tasks.TaskCanceledException : The request was canceled due to the configured HttpClient.Timeout of 100 seconds elapsing.
-------- System.TimeoutException : The operation was canceled.
------------ System.Threading.Tasks.TaskCanceledException : The operation was canceled.
---------------- System.Runtime.InteropServices.JavaScript.JSException : Error: OperationCanceledException
   at System.Net.Http.BrowserHttpInterop.CancellationHelper(Task promise, CancellationToken cancellationToken, JSObject jsController)

This indicates the streaming-request-over-HTTP/1 rejection path that produces TypeError: Failed to fetch is not being hit on CoreCLR-wasm (the request appears to proceed instead of failing fast).

How it was found

Discovered while bringing up the new scheduled Browser + CoreCLR outerloop libraries-test lane (#129436). This [OuterLoop] browser test had never run in CI before (Mono runs innerloop only).

Workaround

The test is being gated to skip on CoreCLR-wasm only, keeping Mono-wasm coverage:

[ActiveIssue("https://github.com/dotnet/runtime/issues/<this-issue>", typeof(PlatformDetection), nameof(PlatformDetection.IsNotMonoRuntime))]

(The test is already [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsBrowser))], so the ActiveIssue only takes effect on Browser + CoreCLR.)

Note

This issue was created by GitHub Copilot on behalf of the user.

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