SignalR Stream is will throw when combined with ToObservable from IX.net, and the stream completes.

public class FooHub : Hub
{
    public IAsyncEnumerable<int> Foo()
    {
        return AsyncEnumerable.Empty<int>();
    }
}

public static class Program
{
    public async Task Main()
    {
         await new HubConnectionBuilder()
              .WithUrl(....)
             .Build()
             .StreamAsync(nameof(FooHub.Foo))
             .ToObservable()
            .Do(x => Console.WriteLine(x))
            .ToTask();
    }
}

This will throw an exception of CancellationTokenSource ObjectDisposedException.

[BrennanConroy]

Minimal repro without IX.net

var asyncEnumerable = connection.StreamAsyncCore<int>("Stream", new object[] { streamTo });
using var cts = new CancellationTokenSource();
await using var e = asyncEnumerable.GetAsyncEnumerator(cts.Token);
while (await e.MoveNextAsync())
{
}
cts.Cancel();

The issue is that we dispose an internal cts when the server sends a stream completion https://github.com/dotnet/aspnetcore/blob/b4f8e0f587c064b67b99e7ee5f1562fc61ba9242/src/SignalR/clients/csharp/Client.Core/src/HubConnection.cs#L579

Then, if the user cancels a token passed into GetAsyncEnumerator before the enumerator is disposed we will try to cancel the disposed cts from earlier https://github.com/dotnet/aspnetcore/blob/b4f8e0f587c064b67b99e7ee5f1562fc61ba9242/src/SignalR/common/Shared/AsyncEnumerableAdapters.cs#L69

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