Fabric: `fromDynamic`: Parsing vector type when source has no array

Summary:
@public
If some prop has `std::vector` type, it possible that on JS side we want to pass just one element of the array.
And in this case we sometimes drop array initialization (`[]`) part, so instead of passing `[{x:1, y:1}]` we pass `{x:1, y:1}`.
This diff adds support for that.

Reviewed By: mdvacca

Differential Revision: D8526572

fbshipit-source-id: 33d4369ac48cac3eb1c534f477d8259e76e0c547

ReactCommon/fabric/core/propsConversions.h

@@ -26,6 +26,13 @@ inline void fromDynamic(const folly::dynamic &value, std::string &result) { resu
 
 template <typename T>
 inline void fromDynamic(const folly::dynamic &value, std::vector<T> &result) {
+  if (!value.isArray()) {
+    T itemResult;
+    fromDynamic(value, itemResult);
+    result = {itemResult};
+    return;
+  }
+
   result.clear();
   T itemResult;
   for (auto &itemValue : value) {