Assertion in CoroutinesSupport.cs:91

[Nelvin]

Hi Kyrylo,

I stumbled over an Assertion in PrimeTween but I fear it's a really rare edge case and I'm not sure, I can offer enough information to get an idea what happens.

So, when loading a save in the given project, a new scene will be loaded and one script creates a coroutine during it's Start method.
This coroutine spawns another one and that one, then, creates a tween.
If this tween does have a very small duration (0.001f) and is yield returned using ToYieldInstruction() this triggers the assertion - but only in an actual build and not within the Unity IDE.

Simplified code ... this is what happens

class GridManager
{
    void Start()
    {
        ...
        StartCoroutine(LevelManager.instance._StartRound());
        ...
    }
}

class LevelManager
{
    IEnumerator _StartRound()
    {
        ...
        StartCoroutine(ShowRoundPanel());
        ...
    }
    
    IEnumerator ShowRoundPanel()
    {
        yield return Tween.Custom(startValue: 1, endValue: 2, duration: 0.001f).ToYieldInstruction()
    }
}

The assertion doesn't trigger if the duration is bigger or if I add at least a single WaitForEndOfFrame in either of the two nested, parent coroutines or between the creation of the tween and the ToYieldInstruction().

Sadly, I couldn't create an easy setup where this is easy reproducible :/
I can't send the game/project - but attached is the logfile where the assertion and the callstacks can be seen.

I know this is not a lot of info, probably of no help - but I tried for quite some time (due to me having to create a build for each iteration) and the above is where I'm ended at :/

It's not a big issue as I'll just use a workaround - but maybe you have an idea what's going on.

Edit:
Noticed that changing from ToYieldInstruction() to a manual isAlive loop also results in the assertion going away, i.e.

class LevelManager
{
    IEnumerator ShowRoundPanel()
    {
        var tween = Tween.Custom(startValue: 1, endValue: 2, duration: 0.001f);
        while (tween.isAlive)
        {
            yield return new WaitForEndOfFrame();
        }
    }
}

[Nelvin]

Player.log

[KyryloKuzyk]

Huge thanks for reporting the issue!

Unfortunately, I couldn't reproduce the issue in Windows or Android builds no matter what combination I tried. I would very appreciate it if you could help me find a consistent setup which reproduces the issue reliably.

Is there a specific logic before you run _StartRound or ShowRoundPanel that might help find the issue?

[KyryloKuzyk]

@Nelvin any chance you're using a custom coroutine manager? The one that supports pausing and such?

[KyryloKuzyk]

I would still prefer to understand the reason why that particular assertion failed in your case. IEnumerator.Current should only be called after IEnumerator.MoveNext returns true. But seems like your code triggers a corner case where it's not the case. I would still like to debug that.

[Nelvin]

@KyryloKuzyk Sorry for the late reply and thanks a lot for looking into the issue.

The project doesn't use a custom coroutine manager but sadly I ran out of ideas what to do, to narrow it down any further, as I just couldn't replicate in any other way :/

One more detail I now notice is, the tween I used to create the attached logfile, was a dummy custom tween easing from startValue: 1 to endValue: 2 and I was just logging the values in the onValueChange callback. But given the logfile, the startValue value was never set or, at least, the onValueChange callback was never called with the startValue. No idea if this is of any help.