iOS: `removeClippedSubviews` is lost when a view is recycled

[mozzius]

Description

On iOS with the New Architecture, removeClippedSubviews only works the first time a view with it is mounted. When that view is recycled and handed out again for another view with removeClippedSubviews, clipping stays off, so every child stays attached. A ScrollView or FlatList with removeClippedSubviews that is unmounted and mounted again (for example, by navigating away and back) keeps all its rows in the native view hierarchy.

In the repro, a ScrollView with removeClippedSubviews and 100 rows is mounted, unmounted and mounted again. Its content view comes back from the recycle pool (the same instance each time):

	First mount	Each later mount
0.87.1, unmodified	7/100 rows attached	100/100 (3/3)
0.87.1 with the fix	7/100	7/100 (3/3)

Cause

updateProps:oldProps: diffs against the view's own _props, not the oldProps argument (L348). It only sets _removeClippedSubviews when that diff changes (L362):

if (oldViewProps.removeClippedSubviews != newViewProps.removeClippedSubviews) {

prepareForRecycle resets _removeClippedSubviews = NO (L781) but keeps _props. So when a recycled view whose last props had removeClippedSubviews gets it again, the diff sees no change and the flag stays NO: children are mounted straight into the view, and nothing is clipped.

Fix

Compare against _removeClippedSubviews rather than _props. PR to follow.

Steps to reproduce

1. git clone https://github.com/mozzius/view-remove-clipped-subviews-recycle-repro && cd view-remove-clipped-subviews-recycle-repro/ReproducerApp && yarn install
2. cd ios && bundle install && RCT_USE_PREBUILT_RNCORE=0 bundle exec pod install && cd .. (building core from source is only needed for the repro's fix switch)
3. yarn start, then yarn ios
4. On launch, the readout shows #1 stock ... clipping on, 7/100 attached. Tap Remount: #2 stock ... (=#1) clipping OFF, 100/100 attached.
5. Tap fix, then Remount: clipping on, 7/100 attached.

React Native Version

0.87.1. The code is the same on main.

Affected Platforms

Runtime - iOS

Output of npx @react-native-community/cli info

System:
  OS: macOS 27.0.1
IDEs:
  Xcode: 27.0/27A266a
npmPackages:
  react: 19.2.3
  react-native: 0.87.1
iOS:
  hermesEnabled: true
  newArchEnabled: true

Stacktrace or Logs

// first mount
[clip] RCTViewComponentView 0x10825b300 updateProps (stock): removeClippedSubviews=1, _props says 0, ivar is 0 -> toggle
[clip] native state: {"view":"0x000000010825b300","clip":true,"attached":7,"tracked":100}
// unmount
[clip] RCTViewComponentView 0x10825b300 prepareForRecycle: ivar 1 -> 0, _props keeps removeClippedSubviews=1
// mount again
[clip] RCTViewComponentView 0x10825b300 updateProps (stock): removeClippedSubviews=1, _props says 1, ivar is 0 -> no change
[clip] native state: {"view":"0x000000010825b300","clip":false,"attached":100,"tracked":0}

The full logs are in the repro's evidence/.

MANDATORY Reproducer

https://github.com/mozzius/view-remove-clipped-subviews-recycle-repro

Screenshots and Videos

ios-demo.mp4: three remounts on stock, two with the fix, then stock again.