Closing Modal and showing Alert simultaneously locks up app

[jasonmerino]

Description

What I did.

• Had a Modal component visible and attempted to close it and show an Alert at the same time

What I expected to happen

• The Modal component to dismiss as the Alert is being shown

What actually happened

• The app locks up, refreshing the JS bundle doesn't change anything even though it shows the loading bar at the top of the screen.
• No visible error messages in Xcode or in Chrome debugger.

Reproduction

Sample project with reproduction case is here: https://github.com/jasonmerino/ModalAlertCombo

Additional Information

• React Native version: 0.36.0
• Platform: iOS only (simulator and iPhone) (the same code works on Android)
• Operating System: MacOS

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I've done a little debugging on my end and it looks like the issue is with the presenting controller that the Alert is being attached to. When you set a timeout to Alert after the Modal has been fully removed the RCTPresentedViewControllermethod returns the UIViewController rather than the RCTModalHostView.

Not sure why it's functioning as it does, it doesn't crash or anything. It just locks up and the app is unusable.

[nihgwu]

dup of #10471

[jasonmerino]

Closing in favor of #10471