[ASDisplayNode] Propagate traits before loading a subnode (#1234)

#886 enforces that some nodes are loaded before they are sent a visiblity event, but it was not propagating the trait collection before forcing the load.

We are propagating traits in `_setSupernode:` (which was happening after the forced load). I moved the possible forced load to `_setSupernode:`, after propagating traits but before any visibility states are changed.

Source/ASDisplayNode.mm

@@ -2139,6 +2139,18 @@ - (void)_setSupernode:(ASDisplayNode *)newSupernode
       stateToEnterOrExit |= ASHierarchyStateRasterized;
     }
     if (newSupernode) {
+
+      // Now that we have a supernode, propagate its traits to self.
+      // This should be done before possibly forcing self to load so we have traits in -didLoad
+      ASTraitCollectionPropagateDown(self, newSupernode.primitiveTraitCollection);
+
+      if (!parentWasOrIsRasterized && newSupernode.nodeLoaded) {
+        // Trigger the subnode to load its layer, which will create its view if it needs one.
+        // By doing this prior to the downward propagation of newSupernode's interface state,
+        // we can guarantee that -didEnterVisibleState is only called with .isNodeLoaded = YES.
+        [self layer];
+      }
+
       [self enterHierarchyState:stateToEnterOrExit];
 
       // If a node was added to a supernode, the supernode could be in a layout pending state. All of the hierarchy state
@@ -2158,10 +2170,6 @@ - (void)_setSupernode:(ASDisplayNode *)newSupernode
           }
         }
       }
-
-      // Now that we have a supernode, propagate its traits to self.
-      ASTraitCollectionPropagateDown(self, newSupernode.primitiveTraitCollection);
-
     } else {
       // If a node will be removed from the supernode it should go out from the layout pending state to remove all
       // layout pending state related properties on the node
@@ -2260,13 +2268,6 @@ - (void)_insertSubnode:(ASDisplayNode *)subnode atSubnodeIndex:(NSInteger)subnod
     _cachedSubnodes = nil;
   __instanceLock__.unlock();
 
-  if (!isRasterized && self.nodeLoaded) {
-    // Trigger the subnode to load its layer, which will create its view if it needs one.
-    // By doing this prior to downward propagation of .interfaceState in _setSupernode:,
-    // we can guarantee that -didEnterVisibleState is only called with .isNodeLoaded = YES.
-    [subnode layer];
-  }
-
   // This call will apply our .hierarchyState to the new subnode.
   // If we are a managed hierarchy, as in ASCellNode trees, it will also apply our .interfaceState.
   [subnode _setSupernode:self];