NET 10: Breaking change in behaviour when reading HTTP response content

[ign3u5]

Description

HttpContent.LoadIntoBufferAsync now uses LimitArrayPoolWriteStream (here) where it used to use LimitMemoryStream (here) in .NET 9.

LimitArrayPoolWriteStream.WriteAsync ignores the CancellationToken and simply returns Task.CompletedTask (here) where LimitMemoryStream.WriteAsync calls the base functionality (here) which returns a cancelled task (here).

This change in behaviour means that where, in .NET 9, a TaskCanceledException would be thrown; in .NET 10 the completed task is returned successfully.

Reproduction Steps

var httpClient = new HttpClient(new SomeHandler());

var cts = new CancellationTokenSource();

cts.Cancel();

_ = await httpClient.GetAsync("https://example.com", cts.Token);

public class SomeHandler : HttpMessageHandler
{
    protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
    {
        return Task.FromResult(new HttpResponseMessage()
        {
            Content = new StringContent("Hello from SomeHandler")
        });
    }
}

Expected behavior

Behaviour in .NET 9 - TaskCanceledException is thrown.

Actual behavior

Behaviour in .NET 10 - No exception is thrown.

Regression?

This demonstrates a regression / breaking change between the versions.

Known Workarounds

No response

Configuration

• Used .NET 9 and 10

Other information

No response

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[ManickaP]

@MihaZupan looks like #109642

[MihaZupan]

We can add back the CancellationToken checks in those write helpers, but I don't really see this as a big breaking change.

@ign3u5 did this cause you problems in practice? LimitArrayPoolWriteStream is a glorified MemoryStream, where all operations are always synchronous (no need to ever block/wait on anything).
It's normally all the operations that are actually async that you'd care about being cancellable, so you'd honor the cancellation on all the reading before you go to write into this stream.

[ign3u5]

We can add back the CancellationToken checks in those write helpers, but I don't really see this as a big breaking change.

@ign3u5 did this cause you problems in practice? LimitArrayPoolWriteStream is a glorified MemoryStream, where all operations are always synchronous (no need to ever block/wait on anything). It's normally all the operations that are actually async that you'd care about being cancellable, so you'd honor the cancellation on all the reading before you go to write into this stream.

No, nothing functional.
For context, we had a unit test that used a custom message handler to mock the response from a call, we were asserting that it threw an exception which failed when we updated to .NET 10. In actual usage though, this has no impact, as you mentioned.
I mostly raised this issue just to highlight a breaking change that I couldn't see mentioned in the list.