Fix issue where start/end would not be respected in flex edge getters (#1479)

Summary:
Pull Request resolved: https://github.com/facebook/yoga/pull/1479

X-link: https://github.com/facebook/react-native/pull/41682

There are two ways to get the value of a style for a specific edge right now:

1) From the inline start/end edge which is determined via the writing direction (ltr or rtl), assuming you do not have errata on
2) From the flex start/end edge which is determined via the flex direction (row, row-reverse, column, column-reverse)

There is a weird curiosity in the second case: you can define a style to be on the "start" or "end" edge when writing the stylex/css. The physical edge that this refers to is dependent on the writing direction. So `start` would be `left` in `ltr` and `right` in `rtl`, with `end` the opposite. It is **never** determined via the flex direction. Additionally, `start`/`end` takes precedence over the physical edge it corresponds to in the case both are defined.

So, all of this means that to actually get the value of a style from the flex start/end edges, we need to account for the case that one of these relative edges was defined and would overwrite any physical edge. Since this mapping is solely determined by the writing direction, we need to pass that in to all the flex start/end getters and do that logic. This is done in  `flexStartRelativeEdge`/`flexEndRelativeEdge` which was added earlier but for some reason only being used on border.

Reviewed By: NickGerleman

Differential Revision: D51293315

fbshipit-source-id: 26fafff54827134e7c5b10354ff9bfdf67096f5b

yoga/node/Node.cpp

@@ -98,11 +98,29 @@ Edge Node::getInlineEndEdgeUsingErrata(
       : inlineEndEdge(flexDirection, direction);
 }
 
-bool Node::isFlexStartPositionDefined(FlexDirection axis) const {
-  const Edge startEdge = flexStartEdge(axis);
+Edge Node::getFlexStartRelativeEdgeUsingErrata(
+    FlexDirection flexDirection,
+    Direction direction) const {
+  return hasErrata(Errata::StartingEndingEdgeFromFlexDirection)
+      ? Edge::Start
+      : flexStartRelativeEdge(flexDirection, direction);
+}
+
+Edge Node::getFlexEndRelativeEdgeUsingErrata(
+    FlexDirection flexDirection,
+    Direction direction) const {
+  return hasErrata(Errata::StartingEndingEdgeFromFlexDirection)
+      ? Edge::End
+      : flexEndRelativeEdge(flexDirection, direction);
+}
+
+bool Node::isFlexStartPositionDefined(FlexDirection axis, Direction direction)
+    const {
   auto leadingPosition = isRow(axis)
-      ? computeEdgeValueForRow<&Style::position>(Edge::Start, startEdge)
-      : computeEdgeValueForColumn<&Style::position>(startEdge);
+      ? computeEdgeValueForRow<&Style::position>(
+            getFlexStartRelativeEdgeUsingErrata(axis, direction),
+            flexStartEdge(axis))
+      : computeEdgeValueForColumn<&Style::position>(flexStartEdge(axis));
 
   return leadingPosition.isDefined();
 }
@@ -117,11 +135,13 @@ bool Node::isInlineStartPositionDefined(FlexDirection axis, Direction direction)
   return leadingPosition.isDefined();
 }
 
-bool Node::isFlexEndPositionDefined(FlexDirection axis) const {
-  const Edge endEdge = flexEndEdge(axis);
+bool Node::isFlexEndPositionDefined(FlexDirection axis, Direction direction)
+    const {
   auto trailingPosition = isRow(axis)
-      ? computeEdgeValueForRow<&Style::position>(Edge::End, endEdge)
-      : computeEdgeValueForColumn<&Style::position>(endEdge);
+      ? computeEdgeValueForRow<&Style::position>(
+            getFlexEndRelativeEdgeUsingErrata(axis, direction),
+            flexEndEdge(axis))
+      : computeEdgeValueForColumn<&Style::position>(flexEndEdge(axis));
 
   return !trailingPosition.isUndefined();
 }
@@ -136,11 +156,15 @@ bool Node::isInlineEndPositionDefined(FlexDirection axis, Direction direction)
   return trailingPosition.isDefined();
 }
 
-float Node::getFlexStartPosition(FlexDirection axis, float axisSize) const {
-  const Edge startEdge = flexStartEdge(axis);
+float Node::getFlexStartPosition(
+    FlexDirection axis,
+    Direction direction,
+    float axisSize) const {
   auto leadingPosition = isRow(axis)
-      ? computeEdgeValueForRow<&Style::position>(Edge::Start, startEdge)
-      : computeEdgeValueForColumn<&Style::position>(startEdge);
+      ? computeEdgeValueForRow<&Style::position>(
+            getFlexStartRelativeEdgeUsingErrata(axis, direction),
+            flexStartEdge(axis))
+      : computeEdgeValueForColumn<&Style::position>(flexStartEdge(axis));
 
   return resolveValue(leadingPosition, axisSize).unwrapOrDefault(0.0f);
 }
@@ -157,11 +181,15 @@ float Node::getInlineStartPosition(
   return resolveValue(leadingPosition, axisSize).unwrapOrDefault(0.0f);
 }
 
-float Node::getFlexEndPosition(FlexDirection axis, float axisSize) const {
-  const Edge endEdge = flexEndEdge(axis);
+float Node::getFlexEndPosition(
+    FlexDirection axis,
+    Direction direction,
+    float axisSize) const {
   auto trailingPosition = isRow(axis)
-      ? computeEdgeValueForRow<&Style::position>(Edge::End, endEdge)
-      : computeEdgeValueForColumn<&Style::position>(endEdge);
+      ? computeEdgeValueForRow<&Style::position>(
+            getFlexEndRelativeEdgeUsingErrata(axis, direction),
+            flexEndEdge(axis))
+      : computeEdgeValueForColumn<&Style::position>(flexEndEdge(axis));
 
   return resolveValue(trailingPosition, axisSize).unwrapOrDefault(0.0f);
 }
@@ -178,11 +206,15 @@ float Node::getInlineEndPosition(
   return resolveValue(trailingPosition, axisSize).unwrapOrDefault(0.0f);
 }
 
-float Node::getFlexStartMargin(FlexDirection axis, float widthSize) const {
-  const Edge startEdge = flexStartEdge(axis);
+float Node::getFlexStartMargin(
+    FlexDirection axis,
+    Direction direction,
+    float widthSize) const {
   auto leadingMargin = isRow(axis)
-      ? computeEdgeValueForRow<&Style::margin>(Edge::Start, startEdge)
-      : computeEdgeValueForColumn<&Style::margin>(startEdge);
+      ? computeEdgeValueForRow<&Style::margin>(
+            getFlexStartRelativeEdgeUsingErrata(axis, direction),
+            flexStartEdge(axis))
+      : computeEdgeValueForColumn<&Style::margin>(flexStartEdge(axis));
 
   return resolveValue(leadingMargin, widthSize).unwrapOrDefault(0.0f);
 }
@@ -199,11 +231,15 @@ float Node::getInlineStartMargin(
   return resolveValue(leadingMargin, widthSize).unwrapOrDefault(0.0f);
 }
 
-float Node::getFlexEndMargin(FlexDirection axis, float widthSize) const {
-  const Edge endEdge = flexEndEdge(axis);
+float Node::getFlexEndMargin(
+    FlexDirection axis,
+    Direction direction,
+    float widthSize) const {
   auto trailingMargin = isRow(axis)
-      ? computeEdgeValueForRow<&Style::margin>(Edge::End, endEdge)
-      : computeEdgeValueForColumn<&Style::margin>(endEdge);
+      ? computeEdgeValueForRow<&Style::margin>(
+            getFlexEndRelativeEdgeUsingErrata(axis, direction),
+            flexEndEdge(axis))
+      : computeEdgeValueForColumn<&Style::margin>(flexEndEdge(axis));
 
   return resolveValue(trailingMargin, widthSize).unwrapOrDefault(0.0f);
 }
@@ -231,10 +267,10 @@ float Node::getInlineStartBorder(FlexDirection axis, Direction direction)
 }
 
 float Node::getFlexStartBorder(FlexDirection axis, Direction direction) const {
-  const Edge leadRelativeFlexItemEdge = flexStartRelativeEdge(axis, direction);
   YGValue leadingBorder = isRow(axis)
       ? computeEdgeValueForRow<&Style::border>(
-            leadRelativeFlexItemEdge, flexStartEdge(axis))
+            getFlexStartRelativeEdgeUsingErrata(axis, direction),
+            flexStartEdge(axis))
       : computeEdgeValueForColumn<&Style::border>(flexStartEdge(axis));
 
   return maxOrDefined(leadingBorder.value, 0.0f);
@@ -250,10 +286,10 @@ float Node::getInlineEndBorder(FlexDirection axis, Direction direction) const {
 }
 
 float Node::getFlexEndBorder(FlexDirection axis, Direction direction) const {
-  const Edge trailRelativeFlexItemEdge = flexEndRelativeEdge(axis, direction);
   YGValue trailingBorder = isRow(axis)
       ? computeEdgeValueForRow<&Style::border>(
-            trailRelativeFlexItemEdge, flexEndEdge(axis))
+            getFlexEndRelativeEdgeUsingErrata(axis, direction),
+            flexEndEdge(axis))
       : computeEdgeValueForColumn<&Style::border>(flexEndEdge(axis));
 
   return maxOrDefined(trailingBorder.value, 0.0f);
@@ -275,10 +311,10 @@ float Node::getFlexStartPadding(
     FlexDirection axis,
     Direction direction,
     float widthSize) const {
-  const Edge leadRelativeFlexItemEdge = flexStartRelativeEdge(axis, direction);
   auto leadingPadding = isRow(axis)
       ? computeEdgeValueForRow<&Style::padding>(
-            leadRelativeFlexItemEdge, flexStartEdge(axis))
+            getFlexStartRelativeEdgeUsingErrata(axis, direction),
+            flexStartEdge(axis))
       : computeEdgeValueForColumn<&Style::padding>(flexStartEdge(axis));
 
   return maxOrDefined(resolveValue(leadingPadding, widthSize).unwrap(), 0.0f);
@@ -300,10 +336,10 @@ float Node::getFlexEndPadding(
     FlexDirection axis,
     Direction direction,
     float widthSize) const {
-  const Edge trailRelativeFlexItemEdge = flexEndRelativeEdge(axis, direction);
   auto trailingPadding = isRow(axis)
       ? computeEdgeValueForRow<&Style::padding>(
-            trailRelativeFlexItemEdge, flexEndEdge(axis))
+            getFlexEndRelativeEdgeUsingErrata(axis, direction),
+            flexEndEdge(axis))
       : computeEdgeValueForColumn<&Style::padding>(flexEndEdge(axis));
 
   return maxOrDefined(resolveValue(trailingPadding, widthSize).unwrap(), 0.0f);