FIX: 'Should have drop target' asserts (case 1229146, #1107).

Author: Rene Damm

Packages/com.unity.inputsystem/CHANGELOG.md

@@ -28,6 +28,7 @@ however, it has to be formatted properly to pass verification tests.
 - Actions and bindings in the `.inputactions` editor are no longer force-expanded on every domain reload and whenever a new action or binding is added.
 - The importer for `.inputactions` assets will now check out from version control the generated .cs file when overwriting it – which only happens if the contents differ ([case 1222972](https://issuetracker.unity3d.com/issues/inputsystem-editor-generated-c-number-file-is-not-checked-out-when-overwriting)).
 - The editor for `.inputactions` assets will now check out from version control the asset before saving it.
+- Drag-reordering action maps no longer throws "Should have drop target" asserts in the console (case [1229146](https://issuetracker.unity3d.com/issues/inputsystem-reordering-of-actionmaps-in-input-action-window-fails-and-throws-should-have-drop-target-error)).
 
 ### Changed
 

Packages/com.unity.inputsystem/InputSystem/Editor/AssetEditor/InputActionTreeView.cs

@@ -471,7 +471,7 @@ protected override DragAndDropVisualMode HandleDragAndDrop(DragAndDropArgs args)
                 var assignNewIDs = !(isMove && sourceTree == this);
 
                 // Determine where we are moving/copying the data.
-                var target = (args.parentItem ?? rootItem) as ActionTreeItemBase;
+                var target = args.parentItem ?? rootItem;
                 int? childIndex = null;
                 if (args.dragAndDropPosition == DragAndDropPosition.BetweenItems)
                     childIndex = args.insertAtIndex;
@@ -770,15 +770,15 @@ Type CopyTagToType(string tagName)
             {
                 // Paste into InputActionAsset.
                 array = serializedObject.FindProperty("m_ActionMaps");
-                arrayIndex = array.arraySize;
+                arrayIndex = location.childIndex ?? array.arraySize;
             }
             else
             {
                 throw new InvalidOperationException($"Cannot paste {tag} into {location.item.displayName}");
             }
 
             // If not given a specific index, we paste onto the end of the array.
-            if (arrayIndex == -1)
+            if (arrayIndex == -1 || arrayIndex > array.arraySize)
                 arrayIndex = array.arraySize;
 
             var actionForNewBindings = location.item is ActionTreeItem actionItem ? actionItem.name : null;