Fix handling of negative flex gap (#39596)

Summary:
Pull Request resolved: #39596

X-link: react/yoga#1405

I noticed that we weren't clamping negative flex gap values to zero. This fixes that bug.

Reviewed By: rshest

Differential Revision: D49530494

fbshipit-source-id: 069db7312f72a085c5c4b01ead7bc66a353a07e5

Author: NickGerleman

packages/react-native/ReactCommon/yoga/yoga/algorithm/CalculateLayout.cpp

@@ -1215,7 +1215,7 @@ static void justifyMainAxis(
       node->getLeadingPaddingAndBorder(mainAxis, ownerWidth).unwrap();
   const float trailingPaddingAndBorderMain =
       node->getTrailingPaddingAndBorder(mainAxis, ownerWidth).unwrap();
-  const float gap = node->getGapForAxis(mainAxis, ownerWidth).unwrap();
+  const float gap = node->getGapForAxis(mainAxis, ownerWidth);
   // If we are using "at most" rules in the main axis, make sure that
   // remainingFreeSpace is 0 when min main dimension is not given
   if (measureModeMainDim == MeasureMode::AtMost &&
@@ -1666,8 +1666,7 @@ static void calculateLayoutImpl(
       generationCount);
 
   if (childCount > 1) {
-    totalMainDim +=
-        node->getGapForAxis(mainAxis, availableInnerCrossDim).unwrap() *
+    totalMainDim += node->getGapForAxis(mainAxis, availableInnerCrossDim) *
         static_cast<float>(childCount - 1);
   }
 
@@ -1692,7 +1691,7 @@ static void calculateLayoutImpl(
   float totalLineCrossDim = 0;
 
   const float crossAxisGap =
-      node->getGapForAxis(crossAxis, availableInnerCrossDim).unwrap();
+      node->getGapForAxis(crossAxis, availableInnerCrossDim);
 
   // Max main dimension of all the lines.
   float maxLineMainDim = 0;

packages/react-native/ReactCommon/yoga/yoga/algorithm/FlexLine.cpp

@@ -33,7 +33,7 @@ FlexLine calculateFlexLine(
   const FlexDirection mainAxis = resolveDirection(
       node->getStyle().flexDirection(), node->resolveDirection(ownerDirection));
   const bool isNodeFlexWrap = node->getStyle().flexWrap() != Wrap::NoWrap;
-  const float gap = node->getGapForAxis(mainAxis, availableInnerWidth).unwrap();
+  const float gap = node->getGapForAxis(mainAxis, availableInnerWidth);
 
   // Add items to the current line until it's full or we run out of items.
   for (; endOfLineIndex < node->getChildren().size(); endOfLineIndex++) {

packages/react-native/ReactCommon/yoga/yoga/node/Node.cpp

@@ -202,13 +202,13 @@ FloatOptional Node::getMarginForAxis(
   return getLeadingMargin(axis, widthSize) + getTrailingMargin(axis, widthSize);
 }
 
-FloatOptional Node::getGapForAxis(
-    const FlexDirection axis,
-    const float widthSize) const {
+float Node::getGapForAxis(const FlexDirection axis, const float widthSize)
+    const {
   auto gap = isRow(axis)
-      ? computeColumnGap(style_.gap(), CompactValue::ofZero())
-      : computeRowGap(style_.gap(), CompactValue::ofZero());
-  return yoga::resolveValue(gap, widthSize);
+      ? computeColumnGap(style_.gap(), CompactValue::ofUndefined())
+      : computeRowGap(style_.gap(), CompactValue::ofUndefined());
+  auto resolvedGap = yoga::resolveValue(gap, widthSize);
+  return maxOrDefined(resolvedGap.unwrap(), 0);
 }
 
 YGSize Node::measure(

packages/react-native/ReactCommon/yoga/yoga/node/Node.h

@@ -231,8 +231,7 @@ class YG_EXPORT Node : public ::YGNode {
   FloatOptional getMarginForAxis(
       const FlexDirection axis,
       const float widthSize) const;
-  FloatOptional getGapForAxis(const FlexDirection axis, const float widthSize)
-      const;
+  float getGapForAxis(const FlexDirection axis, const float widthSize) const;
   // Setters
 
   void setContext(void* context) {