Resolve the container view before the unmount assertions read superview

patches/react-native/details.md

@@ -339,3 +339,11 @@
 - Upstream PR/issue: https://github.com/react/react-native/pull/57546 (merged as `06eb1fe`)
 - E/App issue: https://github.com/Expensify/App/issues/97127
 - PR introducing patch: https://github.com/Expensify/App/pull/98095
+
+### [react-native+0.86.0+042+fix-unmount-assert-container-view.patch](react-native+0.86.0+042+fix-unmount-assert-container-view.patch)
+
+- Reason: `-[RCTViewComponentView unmountChildComponentView:index:]` asserts `childComponentView.superview == self.currentContainerView`, but `currentContainerView` is not a pure getter. When `_useCustomContainerView` flips it creates or tears down `_containerView` and moves the existing subviews across, so reading it mutates the very hierarchy the assertion is inspecting. The order in which the two operands of `==` are evaluated is unspecified, so `superview` can be read before the migration runs and the check then compares a pre-migration superview against the post-migration container view. The `[childComponentView removeFromSuperview]` immediately afterwards is unaffected, which is why this only ever surfaces as an assertion failure and never as broken rendering. `_useCustomContainerView` is recomputed on every `finalizeUpdates` from `styleWouldClipOverflowInk`, so any view whose style crosses that threshold while it has mounted children is exposed. The patch resolves the container view into a local before the assertions read `superview`.
+- Symptom: `SIGABRT`, `NSInternalInconsistencyException: Attempt to unmount a view which is mounted inside a different view.` The reported `existing parent` tag equals the parent's own tag, which is the tell that the child really is inside the parent, just not inside the parent's container view. `RCTAssert` compiles out where `NS_BLOCK_ASSERTIONS` is set, so only builds that keep assertions on abort here.
+- Upstream PR/issue: This should ideally be fixed upstream, but no PR has been filed yet.
+- E/App issue: [#100008](https://github.com/Expensify/App/issues/100008) [#98970](https://github.com/Expensify/App/issues/98970) — first seen while bulk-duplicating reports on iOS, but not specific to that flow and it reproduces on `main`
+- PR introducing patch: https://github.com/Expensify/App/pull/100016

patches/react-native/react-native+0.86.0+042+fix-unmount-assert-container-view.patch

@@ -0,0 +1,43 @@
+diff --git a/node_modules/react-native/React/Fabric/Mounting/ComponentViews/View/RCTViewComponentView.mm b/node_modules/react-native/React/Fabric/Mounting/ComponentViews/View/RCTViewComponentView.mm
+index 22c6a3c..eeaa8ff 100644
+--- a/node_modules/react-native/React/Fabric/Mounting/ComponentViews/View/RCTViewComponentView.mm
++++ b/node_modules/react-native/React/Fabric/Mounting/ComponentViews/View/RCTViewComponentView.mm
+@@ -175,6 +175,12 @@ static BOOL RCTLayerTransformCollapsesAxis(CALayer *layer)
+   if (_removeClippedSubviews) {
+     [_reactSubviews removeObjectAtIndex:index];
+   } else {
++    // `currentContainerView` is not a pure getter: it moves the existing subviews across whenever the custom
++    // container view is created or torn down. Resolve it once, before `superview` is read, so every assertion below
++    // compares state from the same side of that migration. Left as `self.currentContainerView` the `==` operands may
++    // be evaluated in either order, and a pre-migration `superview` then gets compared against the post-migration
++    // container view.
++    UIView *containerView = self.currentContainerView;
+     RCTAssert(
+         childComponentView.superview != nil,
+         @"Attempt to unmount a view which is not mounted. (parent: %@, child: %@, index: %@)",
+@@ -182,21 +188,20 @@ static BOOL RCTLayerTransformCollapsesAxis(CALayer *layer)
+         childComponentView,
+         @(index));
+     RCTAssert(
+-        childComponentView.superview == self.currentContainerView,
++        childComponentView.superview == containerView,
+         @"Attempt to unmount a view which is mounted inside a different view. (parent: %@, child: %@, index: %@, existing parent: %@)",
+         self,
+         childComponentView,
+         @(index),
+         @([childComponentView.superview tag]));
+     RCTAssert(
+-        (self.currentContainerView.subviews.count > index) &&
+-            [self.currentContainerView.subviews objectAtIndex:index] == childComponentView,
++        (containerView.subviews.count > index) && [containerView.subviews objectAtIndex:index] == childComponentView,
+         @"Attempt to unmount a view which has a different index. (parent: %@, child: %@, index: %@, actual index: %@, tag at index: %@)",
+         self,
+         childComponentView,
+         @(index),
+-        @([self.currentContainerView.subviews indexOfObject:childComponentView]),
+-        @([[self.currentContainerView.subviews objectAtIndex:index] tag]));
++        @([containerView.subviews indexOfObject:childComponentView]),
++        @([[containerView.subviews objectAtIndex:index] tag]));
+   }
+
+   [childComponentView removeFromSuperview];