Fix up some small issues with YGUnitAuto

Summary: There are still some pieces of RN which does not handle YGUnitAuto and makes use of either the value being nan or the unit being undefined. This diff makes this more robust to those kinds of situations.

Reviewed By: wwjholmes

Differential Revision: D4567045

fbshipit-source-id: ace5fd89bd534a6bb5ec7dba0c3afbf13d62d7c9

Author: Emil Sjolander

yoga/Yoga.c

@@ -434,7 +434,7 @@ inline float YGNodeStyleGetFlexShrink(const YGNodeRef node) {
 }
 
 static inline const YGValue *YGNodeStyleGetFlexBasisPtr(const YGNodeRef node) {
-  if (node->style.flexBasis.unit != YGUnitAuto) {
+  if (node->style.flexBasis.unit != YGUnitAuto && node->style.flexBasis.unit != YGUnitUndefined) {
     return &node->style.flexBasis;
   }
   if (!YGFloatIsUndefined(node->style.flex) && node->style.flex > 0.0f) {
@@ -477,7 +477,7 @@ void YGNodeStyleSetFlex(const YGNodeRef node, const float flex) {
         node->style.instanceName.unit != YGUnitPoint) {                              \
       node->style.instanceName.value = paramName;                                    \
       node->style.instanceName.unit =                                                \
-          YGFloatIsUndefined(paramName) ? YGUnitUndefined : YGUnitPoint;             \
+          YGFloatIsUndefined(paramName) ? YGUnitAuto : YGUnitPoint;                  \
       YGNodeMarkDirtyInternal(node);                                                 \
     }                                                                                \
   }                                                                                  \
@@ -487,7 +487,7 @@ void YGNodeStyleSetFlex(const YGNodeRef node, const float flex) {
         node->style.instanceName.unit != YGUnitPercent) {                            \
       node->style.instanceName.value = paramName;                                    \
       node->style.instanceName.unit =                                                \
-          YGFloatIsUndefined(paramName) ? YGUnitUndefined : YGUnitPercent;           \
+          YGFloatIsUndefined(paramName) ? YGUnitAuto : YGUnitPercent;                \
       YGNodeMarkDirtyInternal(node);                                                 \
     }                                                                                \
   }
@@ -496,7 +496,7 @@ void YGNodeStyleSetFlex(const YGNodeRef node, const float flex) {
   void YGNodeStyleSet##name(const YGNodeRef node, const type paramName) {                         \
     if (node->style.instanceName.value != paramName ||                                            \
         node->style.instanceName.unit != YGUnitPoint) {                                           \
-      node->style.instanceName.value = YGFloatIsUndefined(paramName) ? YGUndefined : paramName;   \
+      node->style.instanceName.value = paramName;                                                 \
       node->style.instanceName.unit = YGFloatIsUndefined(paramName) ? YGUnitAuto : YGUnitPoint;   \
       YGNodeMarkDirtyInternal(node);                                                              \
     }                                                                                             \
@@ -505,7 +505,7 @@ void YGNodeStyleSetFlex(const YGNodeRef node, const float flex) {
   void YGNodeStyleSet##name##Percent(const YGNodeRef node, const type paramName) {                \
     if (node->style.instanceName.value != paramName ||                                            \
         node->style.instanceName.unit != YGUnitPercent) {                                         \
-      node->style.instanceName.value = YGFloatIsUndefined(paramName) ? YGUndefined : paramName;   \
+      node->style.instanceName.value = paramName;                                                 \
       node->style.instanceName.unit = YGFloatIsUndefined(paramName) ? YGUnitAuto : YGUnitPercent; \
       YGNodeMarkDirtyInternal(node);                                                              \
     }                                                                                             \

yoga/Yoga.h

@@ -44,7 +44,7 @@ typedef struct YGValue {
 } YGValue;
 
 static const YGValue YGValueUndefined = {YGUndefined, YGUnitUndefined};
-static const YGValue YGValueAuto = {0, YGUnitAuto};
+static const YGValue YGValueAuto = {YGUndefined, YGUnitAuto};
 
 typedef struct YGNode *YGNodeRef;
 typedef YGSize (*YGMeasureFunc)(YGNodeRef node,