FakeTimeProvider.AutoAdvanceAmount doesn't seem to work with Task.Delay

[xdeng-msft]

Description

The program would enter an infinite loop when a task delay is created with a FakeTimeProvider with AutoAdvanceAmount configured. I am not entirely sure what's going on, and I tried setting the SynchronizationContext to null & ConfigureAwate(true) but none of them seem to work.

Reproduction Steps

public static async Task Main(string[] args)
{
    FakeTimeProvider timeProvider = new FakeTimeProvider();
    timeProvider.AutoAdvanceAmount = TimeSpan.FromSeconds(10);
    await Task.Delay(TimeSpan.FromSeconds(3), timeProvider);

    await Console.Out.WriteLineAsync("123");
}

Notice that the Console output would never appear as the program is still waiting for the Task.Delay to complete.

Expected behavior

Task.Delay completes immediately as the time provider is configured with an AutoAdvanceAmount that's larger than the delay.

Actual behavior

program waiting for the Task.Delay to complete indefinitely.

Regression?

N/A

Known Workarounds

N/A

Configuration

No response

Other information

Microsoft.Extensions.TimeProvider.Testing 9.7.0 on .net 8

[MihuBot]

Possible related and/or duplicate issue:

• Changing FakeTimeProvider's current time during a timer callback can lead to lack of forward progress #4275

[omsoftdev]

The "Expected behavior" is incorrect because the FakeTimeProvider instance is not changed anywhere.
AutoAdvanceAmount is the amount of time by which time advances whenever the clock is read. Reading the current time from the fake time provider triggers the auto-advance of the internal clock.

The following code unblocks the task:

    public static async Task Main(string[] args)
    {
        FakeTimeProvider timeProvider = new FakeTimeProvider();
        timeProvider.AutoAdvanceAmount = TimeSpan.FromSeconds(10);
        var waitTask = Task.Delay(TimeSpan.FromSeconds(3), timeProvider);

        // timeProvider.GetUtcNow() call triggers the auto-advance of the fake time provider:
        Console.WriteLine("Current time: " + timeProvider.GetUtcNow());

        await waitTask;
        await Console.Out.WriteLineAsync("123");
    }