[BUG] ReactiveCommand's IsExecuting is not set to true if it's executed again after throwing an exception

[n-ski]

Describe the bug
If a command throws an exception and it gets executed again later, IsExecuting will remain false.

Steps To Reproduce
Basically added 2 lines of code to an existing test.

[Fact]
public async Task CommandIsExecutingTest()
{
    var subj = new Subject<Unit>();
    bool isExecuting = false;
    Exception? fail = null;
    var fixture = ReactiveCommand.CreateFromTask(async () =>
    {
        await subj.Take(1);
        throw new Exception();
    });
    fixture.IsExecuting.Subscribe(x => isExecuting = x);
    fixture.ThrownExceptions.Subscribe(ex => fail = ex);

    Assert.False(isExecuting);
    Assert.Null(fail);

    fixture.Execute().Subscribe();
    Assert.True(isExecuting);
    Assert.Null(fail);

    subj.OnNext(Unit.Default);

    // Wait 1 ms to allow execution to complete
    await Task.Delay(1).ConfigureAwait(false);

    Assert.False(isExecuting);
    Assert.NotNull(fail);

    fixture.Execute().Subscribe();
    Assert.True(isExecuting); // Fails here.
}

Expected behaviour
IsExecuting should be true when the command is executing.

Environment

• OS: Windows 10, .NET SDK 5.0.206, Runtime 5.0.9
• ReactiveUI Version: 15.1.1

[ChrisPulman]

We are trying to come up with a resolve for this but the root cause is in the System.Reactive code
dotnet/reactive#1256
This issue has been outstanding for quite some time.

[sijk]

For what it's worth, if anyone else is trying to work around this issue, the following approach of explicitly catching the exception within the command observable worked for me:

Subject<Exception> _exceptions = new();

CancelableCommand = ReactiveCommand.CreateFromObservable(
    () => Observable
        .StartAsync(DoSomethingAsync)
        .TakeUntil(CancelCommand)
        .ObserveOn(RxApp.MainThreadScheduler)
        .Catch((Exception ex) =>
        {
            _exceptions.OnNext(ex);
            return Observable.Return(Unit.Default);
        }),
    canExecute);

Then rather than subscribing to CancelableCommand.ThrownExceptions you subscribe to _exceptions.

[glennawatson]

Closing this issue due to it being related to the Rx team not RxUI.

[github-actions]

This issue has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.