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Fix iOS Fabric unmount assertions for zero-sized recycled views #59628

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Fix iOS Fabric unmount assertions for zero-sized recycled views #59628

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7ba685e
Fix iOS Fabric unmount assertions for zero-sized recycled views
theeket Oct 29, 2026
6002b87
update according to the suggestion
theeket Oct 30, 2026
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7 changes: 5 additions & 2 deletions packages/react-native/React/Fabric/Mounting/ComponentViews/View/RCTViewComponentView.mm
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Original file line number Diff line number Diff line change
Expand Up @@ -243,21 +243,24 @@ - (void)unmountChildComponentView:(UIView<RCTComponentViewProtocol> *)childCompo
if (_removeClippedSubviews) {
[_reactSubviews removeObjectAtIndex:index];
} else {
// This getter can migrate children from a recycled clipping container.
// Reconcile before reading superview, even when assertions are disabled.
[[maybe_unused]] UIView *containerView = self.currentContainerView;
RCTAssert(
childComponentView.superview != nil,
@"Attempt to unmount a view which is not mounted. (parent: %@, child: %@, index: %@)",
self,
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]));
#ifndef NS_BLOCK_ASSERTIONS
NSArray<UIView *> *containerSubviews = self.currentContainerView.subviews;
NSArray<UIView *> *containerSubviews = containerView.subviews;
BOOL isIndexInBounds = index >= 0 && (NSUInteger)index < containerSubviews.count;
RCTAssert(
isIndexInBounds && [containerSubviews objectAtIndex:index] == childComponentView,
Expand Down
53 changes: 53 additions & 0 deletions packages/react-native/React/Tests/Mounting/RCTViewComponentViewUnmountTests.mm
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,9 @@
#import <React/RCTAssert.h>
#import <React/RCTViewComponentView.h>
#import <XCTest/XCTest.h>
#import <react/renderer/components/view/ViewProps.h>

using namespace facebook::react;

@interface RCTViewComponentViewUnmountTests : XCTestCase
@end
Expand Down Expand Up @@ -83,4 +86,54 @@ - (void)testUnmountWithInBoundsMismatchStillReportsTagAtIndex
XCTAssertNotEqualObjects(thrownName, NSRangeException);
}

// A recycled view can receive children before its own props are updated. If
// the new owner is zero-sized, layer invalidation does not reconcile the old
// clipping container. Unmount must do so before checking the child's parent.
- (void)testUnmountReconcilesRecycledContainerAtZeroSize
{
RCTViewComponentView *parent = [[RCTViewComponentView alloc] initWithFrame:CGRectZero];
auto clippingProps = std::make_shared<ViewProps>();
clippingProps->yogaStyle.setOverflow(facebook::yoga::Overflow::Hidden);
clippingProps->outlineWidth = 1;
[parent updateProps:clippingProps oldProps:parent.props];
[parent finalizeUpdates:RNComponentViewUpdateMaskAll];

RCTViewComponentView *previousChild = [RCTViewComponentView new];
[parent mountChildComponentView:previousChild index:0];
UIView *previousContainer = previousChild.superview;
XCTAssertNotEqual(previousContainer, parent);
XCTAssertNotNil(previousContainer);
[parent unmountChildComponentView:previousChild index:0];
[parent prepareForRecycle];

// Fabric mounts descendants before applying the recycled parent's new props.
RCTViewComponentView *child = [RCTViewComponentView new];
[parent mountChildComponentView:child index:0];
[parent updateProps:std::make_shared<ViewProps>() oldProps:parent.props];
[parent finalizeUpdates:RNComponentViewUpdateMaskAll];
XCTAssertTrue(CGSizeEqualToSize(parent.bounds.size, CGSizeZero));
XCTAssertEqual(child.superview, previousContainer);

NSString *message = nil;
NSString *thrownName = RCTUnmountAndReportAssert(parent, child, 0, &message);

XCTAssertNil(message, @"Container migration must precede the ownership check");
XCTAssertNil(thrownName);
XCTAssertNil(child.superview);
XCTAssertNil(previousContainer.superview, @"The stale container must be removed");
}

- (void)testUnmountStillReportsChildMountedUnderAnotherParent
{
RCTViewComponentView *parent = [RCTViewComponentView new];
RCTViewComponentView *otherParent = [RCTViewComponentView new];
RCTViewComponentView *child = [RCTViewComponentView new];
[otherParent mountChildComponentView:child index:0];

NSString *message = nil;
RCTUnmountAndReportAssert(parent, child, 0, &message);

XCTAssertTrue([message containsString:@"mounted inside a different view"]);
}

@end
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