This PR is not cleanest solution however intended to provide suggestion on fix which core team may can address in best way possible. This modification has been tested pretty rigorously and has been found to be the type of fix needed to solve the issue mentioned.

Ideally we could use https://developer.apple.com/documentation/uikit/uiviewcontroller/1621505-dismissviewcontrolleranimated with the completion handler to ensure it's fully closed in that particular condition. Not sure if worth the trouble since usually this particular condition just needs to fully close (with no animation) before opening again (and the timeout here ensures that as well as appears to fully correct the situation) but perhaps the completion handler's could be used to tighten all this up and avoid race conditions in the most sure fire way.

@NathanWalker Indeed this fix doesn't look clean. It's not clear how the problem of a viewController not having a view is fixed by closing a modal view on the same viewController. Perhaps this fixes a certain scenario, but it's not immediately clear what it is.

My guess is that you are trying to open a modal view on a target that already opened a modal view. The iOS framework doesn't allow this by default and we are currently not supporting this. If indeed this is the case, we can discuss further if this is indeed a desirable behavior.

Agreed @MartoYankov - I assume that your team also believed a modal needed to be closed in that condition though hence the message you all had in there:

Parent page is not part of the window hierarchy. Close the current modal page before showing another one!

So instead of just logging a message I did just that: closed the current modal. Again it appears to fix it - why it fixes it not sure but it's a definite race condition that I've had trouble reproducing really over the past year to year and half as I've run into from time to time in all sorts of {N} projects.

Bottom line I believe is that the message that was there (is there currently alludes to the situation), let's just handle and not let apps fail on that condition.

Reproducing it or providing a test for it - I wish I knew - race conditions are tough.

Hey @NathanWalker

I have done some tests and managed to reproduce the "Close the current modal page before showing another one!" error consistently in 2 scenarios:

1. Open a modal page in the closeCallback of another modal page

The issue here is that we fire the closeCallback before the closing animation is completed. As you suggested - I tried using the dismissViewControllerAnimatedCompletion and fire the callback in the completion handler. This seems to resolve the issue. 🎉
Also related to #5744

2. Open a modal page while another one is opened

The issue here is the same as before - there is already modally presented view controller, so we cannot present another one. The solution might be to have a parameter forceCloseOpenedModal in the showModal() method. The implementation should trigger a close on the current modal and use the completion callback (as in the previous case) to show the new modal. The value of this "force" param can also be true by default, which will make it behave much like what you are aiming with this PR.

Here is the branch that I have been experimenting with:

• Problem 1 is resolved thanks to dismissViewControllerAnimatedCompletion
• There are repro of both problems 1. and 2. in the test-app.

Next Steps

This PR triggered a good discussion. One thing is sure - setTimeout(openNow(), 300); is not the right approach here - that's why I'm closing this PR.
What's next:

1. Work on a PR based on dismissViewControllerAnimatedCompletion to resolve iOS: issue when trying to chain modal pages within promise #5744 (problem 1)
2. Work on on the forceClose option (problem 2). We can set it to true by default or make angular always pass true when showing modals.
3. Once the above are done. Let's see if there are more "view-hierarchy stability" issues that developers can easily hit.

Your help is much appreciated if you want to contribute on this plan.

@vakrilov hooray! this is great news thank you so much for digging into this one 🤗
Love your proposal 1 & 2 in next steps - I'll definitely try to help on those when I can.

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