From 6de547f3fd9ecb59a12392bd180f3a17ecb094ce Mon Sep 17 00:00:00 2001
From: Open Source Bot <generatedunixname499836121@meta.com>
Date: Mon, 2 Nov 2026 14:00:22 -0800
Subject: [PATCH] Fix style keywords reading back as the wrong unit after a
 non-integer size (#2056) (#59745)

Summary:

## Summary

Fixes #2052.

Replacing a non-integer size with `max-content`, `fit-content`, or `stretch` could make the getter return a different keyword. `YGNodeStyleSetHeight(node, 0.5f)`, then `YGNodeStyleSetWidth(node, 0.25f)`, then `YGNodeStyleSetWidthMaxContent(node)` made `YGNodeStyleGetWidth` return `YGUnitFitContent` instead of `YGUnitMaxContent`.

A non-integer size is stored in the value pool, and the handle keeps that pool index in its value bits. `storeKeyword` changed the type to `Keyword` but left the indexed bit set, so `isKeyword` compared the pool index with the keyword enum (`MaxContent` = 0, `FitContent` = 1, `Stretch` = 2). The same mismatch affects height, min and max size, and flex-basis. A pool index of 3 or more matches no keyword and hits the debug assert in `getSize`.

`auto`, `undefined`, margin, and padding read the type bits only, so those getters were already correct. `storeKeyword` still writes the keyword into the handle's existing pool slot. `getSize` now reads that slot when the indexed bit is set, so the handle keeps the slot and the getter returns the stored keyword.

## Test plan

- `YogaTest.width_keyword_replaces_pooled_number` covers the #2052 sequence.
- `StyleValuePool.store_keywords_after_large_int` checks max-content, fit-content, and stretch in pool slots 0 through 3.
- `StyleValuePool.store_large_int_and_keyword_repeatedly` switches a pooled number and max-content 5000 times and checks that the slot is reused.
- `./unit_tests Debug`: 880 passed, 0 failed. Baseline before these tests was 877 passed, 0 failed.

Changelog:
[General][Fixed] - Fix reading back max-content, fit-content, and stretch after a non-integer size was stored

Reviewed By: javache

Differential Revision: D128898045
---
 .../yoga/yoga/style/StyleValueHandle.h          |  4 ----
 .../yoga/yoga/style/StyleValuePool.h            | 17 ++++++++++++++---
 2 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/packages/react-native/ReactCommon/yoga/yoga/style/StyleValueHandle.h b/packages/react-native/ReactCommon/yoga/yoga/style/StyleValueHandle.h
index 6a2b58902339..ce622dd059fa 100644
--- a/packages/react-native/ReactCommon/yoga/yoga/style/StyleValueHandle.h
+++ b/packages/react-native/ReactCommon/yoga/yoga/style/StyleValueHandle.h
@@ -76,10 +76,6 @@ class StyleValueHandle {
   // Intentionally leaving out auto as a fast path
   enum class Keyword : uint8_t { MaxContent, FitContent, Stretch };
 
-  constexpr bool isKeyword(Keyword keyword) const {
-    return type() == Type::Keyword && value() == static_cast<uint16_t>(keyword);
-  }
-
   constexpr Type type() const {
     return static_cast<Type>(repr_ & kHandleTypeMask);
   }
diff --git a/packages/react-native/ReactCommon/yoga/yoga/style/StyleValuePool.h b/packages/react-native/ReactCommon/yoga/yoga/style/StyleValuePool.h
index fb31193b9789..c5846658ffb6 100644
--- a/packages/react-native/ReactCommon/yoga/yoga/style/StyleValuePool.h
+++ b/packages/react-native/ReactCommon/yoga/yoga/style/StyleValuePool.h
@@ -89,11 +89,11 @@ class StyleValuePool {
       return StyleSizeLength::undefined();
     } else if (handle.isAuto()) {
       return StyleSizeLength::ofAuto();
-    } else if (handle.isKeyword(StyleValueHandle::Keyword::MaxContent)) {
+    } else if (isKeyword(handle, StyleValueHandle::Keyword::MaxContent)) {
       return StyleSizeLength::ofMaxContent();
-    } else if (handle.isKeyword(StyleValueHandle::Keyword::FitContent)) {
+    } else if (isKeyword(handle, StyleValueHandle::Keyword::FitContent)) {
       return StyleSizeLength::ofFitContent();
-    } else if (handle.isKeyword(StyleValueHandle::Keyword::Stretch)) {
+    } else if (isKeyword(handle, StyleValueHandle::Keyword::Stretch)) {
       return StyleSizeLength::ofStretch();
     } else {
       assert(
@@ -132,6 +132,17 @@ class StyleValuePool {
   }
 
  private:
+  bool isKeyword(StyleValueHandle handle, StyleValueHandle::Keyword keyword)
+      const {
+    if (handle.type() != StyleValueHandle::Type::Keyword) {
+      return false;
+    }
+    // storeKeyword() keeps an existing pool slot, so the keyword may be there
+    uint32_t value = handle.isValueIndexed() ? buffer_.get32(handle.value())
+                                             : handle.value();
+    return value == static_cast<uint32_t>(keyword);
+  }
+
   void storeValue(
       StyleValueHandle& handle,
       float value,