Error when assigning `undefined` to optional view property

[OrfeasZ]

What happened?

I have a nitro view with an optional prop. If I set that prop to a value, and then back to undefined, I get the error seen below.

Reproduceable Code

Repro can be found here: https://github.com/OrfeasZ/nitro-undefined-issue

Video demonstrating the issue: https://i.nofate.me/Kj7yhtil6Ix2gAW4SKM5fl4X.mp4

Steps I took:

1. Create a sample nitro view plugin using create-nitro-module.
2. Make the isRed property optional and run nitrogen.
3. Adjust the relevant Swift code to handle the optional value.
4. Adjust App.tsx to have isRed set to undefined initially.
5. Add buttons to App.tsx to change isRed to have a value and back to undefined.
6. Run the example app and press on Set Red followed by Clear Color.

Relevant log output

Exception in HostFunction: PropTest.isRed: Value is null, expected a boolean

Device

iPhone 16

Nitro Modules Version

0.33.2

Nitrogen Version

0.33.2

Can you reproduce this issue in the Nitro Example app here?

I didn't try (⚠️ your issue might get ignored & closed if you don't try this)

Additional information

• I am using Expo
• I am using nitrogen
• I have read and followed the Troubleshooting Guide.
• I created a reproduction PR to reproduce this issue here in the nitro repo. (See Contributing for more information)
• I searched for similar issues in this repository and found none.

[mrousavy]

Thanks for the repro! I'll look into this

[mrousavy]

Hm, I think it would use std::optional<bool> for conversion, so it should handle nulls just fine: https://github.com/OrfeasZ/nitro-undefined-issue/blob/724180609d559ee9a38d061ebf957c97d71c5195/nitrogen/generated/shared/c%2B%2B/views/HybridPropTestComponent.cpp#L34

Are you 100% sure that you ran nitrogen again and rebuilt the project?

[mrousavy]

Ahhh, the value is null instead of undefined.

Why does React suddenly pass null instead of undefined for undefined props???? Nitrogen expects either undefined or bool, but not null - null is a separate type (nitro::null)... This is very weird.. @hannojg any idea?

[OrfeasZ]

Yep, very weird indeed. And if you look at the video I sent, it even prints undefined correctly in the console just before the crash, so it's probably somewhere in nativeland...

[mrousavy]

Yea it's React giving us null instead of undefined for props.

[camchis]

Also bumping into this issue

It seems like when a fabric view is being updated nextProps are compared against prevProps and a null value is set for any props that have been removed in here

[camchis]

Opened a PR with a potential fix #1189

Happy to hear your thoughts, not sure how else this can be dealt with other than by forcing people to make sure any optional props accept null

  isRed?: boolean | null