fix(fabric): prevent Yoga layout assertion crash in RNGestureHandlerDetectorShadowNode

[AKASH80047]

Description

Fixes #4241

Problem

When dynamically inserting \GestureDetector\ / \ReanimatedSwipeable\ rows into a layout on Fabric (such as inside a list or alongside BottomSheet), \�nyChildHasNewLayout\ can evaluate to false on initial layout passes if child Yoga subtrees have cached layouts. This caused
eact_native_assert(previousLayoutMetrics_.has_value())\ to fail, resulting in a \SIGABRT\ crash.

Solution

• Safely fall back to computing bounding box metrics when \previousLayoutMetrics_\ is \std::nullopt\ instead of asserting.
• Cache \previousLayoutMetrics_ = metrics;\ so subsequent unchanged layout passes can reuse the metrics.
• Preserves Fabric C++ ShadowNode layout semantics across Android and iOS.

Fixes #4241

[coderabbitai]

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Run ID: fc255fd2-4a5f-44ce-9b86-abb3d6539fb6

📥 Commits

Reviewing files that changed from the base of the PR and between 4768ffe and 75676a2.

📒 Files selected for processing (1)

• packages/react-native-gesture-handler/shared/shadowNodes/react/renderer/components/rngesturehandler_codegen/RNGestureHandlerDetectorShadowNode.cpp

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📝 Summary

Summary by CodeRabbit

• Bug Fixes
  • Improved gesture handler layout updates by safely reusing previously calculated layout metrics when no new child layout is available.
  • Prevented potential layout assertion failures during fast-path rendering.

Walkthrough

The layout method now stores computed bounding-box metrics and reuses them only when available. This removes the unconditional optional-value assertion during layout passes without a previous cached value.

Changes

Layout metrics handling

Layer / File(s)	Summary
Cache and guarded reuse packages/react-native-gesture-handler/shared/shadowNodes/react/renderer/components/rngesturehandler_codegen/RNGestureHandlerDetectorShadowNode.cpp	The fast path checks previousLayoutMetrics_ before reuse. Recalculated metrics are stored after the bounding box is applied.

Suggested reviewers: j-piasecki

Priority: ➖ Normal

Severity of issue fixed: Medium

Merge Risk: ⚪ Minimal · up to 75676

This change prevents Fabric layout crashes when gesture-detector rows are dynamically inserted while preserving subsequent layout reuse. No merge-blocking risk remains.

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the Fabric Yoga assertion crash and the affected shadow node. It accurately summarizes the primary change.
Linked Issues check	✅ Passed	The change addresses [#4241] by avoiding the unconditional layout-metrics assertion and caching computed bounding-box metrics for later layout passes. This directly targets the reported Fabric crash.
Out of Scope Changes check	✅ Passed	The pull request changes only the relevant layout-metrics handling in RNGestureHandlerDetectorShadowNode. No unrelated changes are described.

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[Copilot]

🟡 Changes recommended

The new reuse guard relies on previousLayoutMetrics_ semantics, but the clone constructor currently seeds it unconditionally (via getLayoutMetrics()), which can cause incorrect early-return reuse on first layout for cloned nodes.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

This PR addresses a Fabric (New Architecture) crash in RNGestureHandlerDetectorShadowNode by removing a Yoga-layout-dependent assertion and introducing a safe fallback path when previous layout metrics are unavailable, preventing a SIGABRT during dynamic insertion of GestureDetector/ReanimatedSwipeable rows.

Changes:

• Avoids asserting on previousLayoutMetrics_ when anyChildHasNewLayout is false; reuses cached metrics only when present.
• Computes detector bounding-box metrics as a fallback and caches them for subsequent unchanged layout passes.

File summaries

File	Description
packages/react-native-gesture-handler/shared/shadowNodes/react/renderer/components/rngesturehandler_codegen/RNGestureHandlerDetectorShadowNode.cpp	Reworks layout reuse/caching to prevent a null previousLayoutMetrics_ assertion crash and to cache computed bounding-box metrics.

Review details

• Files reviewed: 1/1 changed files
• Comments generated: 1
• Review effort level: Lite

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