Omit null process/diff functions from native VC attributes

Summary:
## Rationale
- **Consistency with Static View Configs**: In Static View Configs, if there isn't a diff or process function, we do not generate a property for it.
- **Type-safety**: The [Flow type for attributes](https://fburl.com/code/tafncg5c), doesn't allow null diff/process functions.

Changelog: [Internal]

Reviewed By: yungsters

Differential Revision: D32152924

fbshipit-source-id: 4156158c5fe09868feec1a0c55aa411d2bd72a27

Libraries/ReactNative/getNativeComponentAttributes.js

@@ -63,8 +63,18 @@ function getNativeComponentAttributes(uiViewClassName: string): any {
     const diff = getDifferForType(typeName);
     const process = getProcessorForType(typeName);
 
+    // If diff or process == null, omit the corresponding property from the Attribute
+    // Why:
+    //  1. Consistency with AttributeType flow type
+    //  2. Consistency with Static View Configs, which omit the null properties
     validAttributes[key] =
-      diff == null && process == null ? true : {diff, process};
+      diff == null
+        ? process == null
+          ? true
+          : {process}
+        : process == null
+        ? {diff}
+        : {diff, process};
   }
 
   // Unfortunately, the current setup declares style properties as top-level