Fix issue where marginStart and marginEnd were not working with rowReverse flex direction (#1420)

Summary:
X-link: https://github.com/facebook/litho/pull/962

X-link: https://github.com/facebook/react-native/pull/40804

Pull Request resolved: https://github.com/facebook/yoga/pull/1420

This stack is ultimately aiming to solve https://github.com/facebook/yoga/issues/1208

**The problem**
Turns out that we do not even check direction when determining which edge is the leading (start) and trailing (end) edges. This is not how web does it as the start/end is based on the writing direction NOT the flex direction: https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_flexible_box_layout/Basic_concepts_of_flexbox#start_and_end_lines. While web does not have marginStart and marginEnd, they do have margin-inline-start/end which relies on the writing mode to determine the "start"/"end": https://developer.mozilla.org/en-US/docs/Web/CSS/margin-inline-start.

This means that if you do something like
```
export default function Playground(props: Props): React.Node {
  return (
    <View style={styles.container}>
      <View style={styles.item} />
    </View>
  );
}

const styles = StyleSheet.create({
  container: {
    marginEnd: 100,
    flexDirection: 'row-reverse',
    backgroundColor: 'red',
    display: 'flex',
    width: 100,
    height: 100,
  },
  item: {
    backgroundColor: 'blue',
    width: 10,
  },
});
```

You get  {F1116264350}
As you can see the margin gets applied to the left edge even thought the direction is ltr and it should be applied to the right edge.

**The solution**
I ended up fixing this by creating a new `leadingLayoutEdge` and `trailingLayoutEdge` function that take the flex direction as well as the direction. Based on the errata, the a few functions will use these new functions to determine which `YGEdge` is the starting/ending.

You might be wondering why I did not put this logic inside of `leadingEdge(flexDirection)` / `trailingEdge(flexDirection)` since other areas could potentially have the same bug like `getLeadingPadding`. These functions are a bit overloaded and there are cases where we actually want to use the flexDirection to get the edge in question. For example, many of the calls to `setLayoutPosition` in `CalculateLayout.cpp` call `leadingEdge()` / `trailingEdge()` to set the proper position for cases like row-reverse where items need to line up in a different direction.

Reviewed By: NickGerleman

Differential Revision: D50140503

fbshipit-source-id: 5b580c7570f6ae1e2d031971926ac4e8f52dd362

yoga/node/Node.cpp

@@ -83,6 +83,22 @@ CompactValue Node::computeEdgeValueForColumn(
   }
 }
 
+YGEdge Node::getLeadingLayoutEdgeUsingErrata(
+    FlexDirection flexDirection,
+    Direction direction) const {
+  return hasErrata(Errata::StartingEndingEdgeFromFlexDirection)
+      ? leadingEdge(flexDirection)
+      : leadingLayoutEdge(flexDirection, direction);
+}
+
+YGEdge Node::getTrailingLayoutEdgeUsingErrata(
+    FlexDirection flexDirection,
+    Direction direction) const {
+  return hasErrata(Errata::StartingEndingEdgeFromFlexDirection)
+      ? trailingEdge(flexDirection)
+      : trailingLayoutEdge(flexDirection, direction);
+}
+
 bool Node::isLeadingPositionDefined(FlexDirection axis) const {
   auto leadingPosition = isRow(axis)
       ? computeEdgeValueForRow(
@@ -117,18 +133,26 @@ float Node::getTrailingPosition(FlexDirection axis, float axisSize) const {
   return resolveValue(trailingPosition, axisSize).unwrapOrDefault(0.0f);
 }
 
-float Node::getLeadingMargin(FlexDirection axis, float widthSize) const {
+float Node::getLeadingMargin(
+    FlexDirection axis,
+    Direction direction,
+    float widthSize) const {
+  const YGEdge startEdge = getLeadingLayoutEdgeUsingErrata(axis, direction);
   auto leadingMargin = isRow(axis)
-      ? computeEdgeValueForRow(style_.margin(), YGEdgeStart, leadingEdge(axis))
-      : computeEdgeValueForColumn(style_.margin(), leadingEdge(axis));
+      ? computeEdgeValueForRow(style_.margin(), YGEdgeStart, startEdge)
+      : computeEdgeValueForColumn(style_.margin(), startEdge);
 
   return resolveValue(leadingMargin, widthSize).unwrapOrDefault(0.0f);
 }
 
-float Node::getTrailingMargin(FlexDirection axis, float widthSize) const {
+float Node::getTrailingMargin(
+    FlexDirection axis,
+    Direction direction,
+    float widthSize) const {
+  const YGEdge endEdge = getTrailingLayoutEdgeUsingErrata(axis, direction);
   auto trailingMargin = isRow(axis)
-      ? computeEdgeValueForRow(style_.margin(), YGEdgeEnd, trailingEdge(axis))
-      : computeEdgeValueForColumn(style_.margin(), trailingEdge(axis));
+      ? computeEdgeValueForRow(style_.margin(), YGEdgeEnd, endEdge)
+      : computeEdgeValueForColumn(style_.margin(), endEdge);
 
   return resolveValue(trailingMargin, widthSize).unwrapOrDefault(0.0f);
 }
@@ -176,7 +200,10 @@ float Node::getTrailingPaddingAndBorder(FlexDirection axis, float widthSize)
 }
 
 float Node::getMarginForAxis(FlexDirection axis, float widthSize) const {
-  return getLeadingMargin(axis, widthSize) + getTrailingMargin(axis, widthSize);
+  // The total margin for a given axis does not depend on the direction
+  // so hardcoding LTR here to avoid piping direction to this function
+  return getLeadingMargin(axis, Direction::LTR, widthSize) +
+      getTrailingMargin(axis, Direction::LTR, widthSize);
 }
 
 float Node::getGapForAxis(FlexDirection axis) const {
@@ -360,18 +387,31 @@ void Node::setPosition(
   const float relativePositionMain = relativePosition(mainAxis, mainSize);
   const float relativePositionCross = relativePosition(crossAxis, crossSize);
 
+  const YGEdge mainAxisLeadingEdge =
+      getLeadingLayoutEdgeUsingErrata(mainAxis, direction);
+  const YGEdge mainAxisTrailingEdge =
+      getTrailingLayoutEdgeUsingErrata(mainAxis, direction);
+  const YGEdge crossAxisLeadingEdge =
+      getLeadingLayoutEdgeUsingErrata(crossAxis, direction);
+  const YGEdge crossAxisTrailingEdge =
+      getTrailingLayoutEdgeUsingErrata(crossAxis, direction);
+
   setLayoutPosition(
-      (getLeadingMargin(mainAxis, ownerWidth) + relativePositionMain),
-      leadingEdge(mainAxis));
+      (getLeadingMargin(mainAxis, direction, ownerWidth) +
+       relativePositionMain),
+      mainAxisLeadingEdge);
   setLayoutPosition(
-      (getTrailingMargin(mainAxis, ownerWidth) + relativePositionMain),
-      trailingEdge(mainAxis));
+      (getTrailingMargin(mainAxis, direction, ownerWidth) +
+       relativePositionMain),
+      mainAxisTrailingEdge);
   setLayoutPosition(
-      (getLeadingMargin(crossAxis, ownerWidth) + relativePositionCross),
-      leadingEdge(crossAxis));
+      (getLeadingMargin(crossAxis, direction, ownerWidth) +
+       relativePositionCross),
+      crossAxisLeadingEdge);
   setLayoutPosition(
-      (getTrailingMargin(crossAxis, ownerWidth) + relativePositionCross),
-      trailingEdge(crossAxis));
+      (getTrailingMargin(crossAxis, direction, ownerWidth) +
+       relativePositionCross),
+      crossAxisTrailingEdge);
 }
 
 YGValue Node::marginLeadingValue(FlexDirection axis) const {