FIX: "ArgumentNullException: Value cannot be null." when deleting a newly created input action (ISXB-1405) (#2129)

Author: jfreire-unity

Packages/com.unity.inputsystem/CHANGELOG.md

@@ -10,6 +10,9 @@ however, it has to be formatted properly to pass verification tests.
 
 ## [Unreleased] - yyyy-mm-dd
 
+### Fixed
+- Fixed an issue where removing a newly created action in the Asset Editor would cause an exception. [UUM-95693](https://issuetracker.unity3d.com/product/unity/issues/guid/UUM-95693)
+
 ## [1.13.0] - 2025-02-05
 
 ### Fixed

Packages/com.unity.inputsystem/InputSystem/Editor/UITKAssetEditor/Commands/Commands.cs

@@ -453,7 +453,7 @@ public static Command DeleteAction(int actionMapIndex, string actionName)
             return (in InputActionsEditorState state) =>
             {
                 var actionMap = Selectors.GetActionMapAtIndex(state, actionMapIndex)?.wrappedProperty;
-                var action = Selectors.GetActionInMap(state, actionMapIndex, actionName).wrappedProperty;
+                var action = Selectors.GetActionInMap(state, actionMapIndex, actionName)?.wrappedProperty;
                 var actionIndex = action.GetIndexOfArrayElement();
                 var actionID = InputActionSerializationHelpers.GetId(action);
                 var isCut = state.IsActionCut(actionMapIndex, actionIndex);
@@ -638,10 +638,17 @@ public static Command ChangeActionName(int actionMapIndex, string oldName, strin
             return (in InputActionsEditorState state) =>
             {
                 var actionMap = Selectors.GetActionMapAtIndex(state, actionMapIndex)?.wrappedProperty;
-                var action = Selectors.GetActionInMap(state, actionMapIndex, oldName).wrappedProperty;
-                InputActionSerializationHelpers.RenameAction(action, actionMap, newName);
-                state.serializedObject.ApplyModifiedProperties();
-                state.m_Analytics?.RegisterActionEdit();
+                var action = Selectors.GetActionInMap(state, actionMapIndex, oldName)?.wrappedProperty;
+                // In an Asset Editor workflow, the serialized property might not exist in case a new action is created
+                // that is yet to be named, and it's deleted before it's named.
+                // This is a particular case when ActionTreeView::DeleteItem triggers
+                // Focus callback -> OnEditTextFinished -> ChangeActionName.
+                if (action != null)
+                {
+                    InputActionSerializationHelpers.RenameAction(action, actionMap, newName);
+                    state.serializedObject.ApplyModifiedProperties();
+                    state.m_Analytics?.RegisterActionEdit();
+                }
                 return state;
             };
         }

Packages/com.unity.inputsystem/InputSystem/Editor/UITKAssetEditor/Views/Selectors.cs

@@ -152,12 +152,17 @@ public static SerializedProperty GetActionForIndex(SerializedProperty actionMap,
             return actionMap.FindPropertyRelative(nameof(InputActionMap.m_Actions)).GetArrayElementAtIndex(actionIndex);
         }
 
-        public static SerializedInputAction GetActionInMap(InputActionsEditorState state, int mapIndex, string name)
+        public static SerializedInputAction? GetActionInMap(InputActionsEditorState state, int mapIndex, string name)
         {
-            return new SerializedInputAction(state.serializedObject
+            SerializedProperty property = state.serializedObject
                 ?.FindProperty(nameof(InputActionAsset.m_ActionMaps))?.GetArrayElementAtIndex(mapIndex)
                 ?.FindPropertyRelative(nameof(InputActionMap.m_Actions))
-                ?.FirstOrDefault(p => p.FindPropertyRelative(nameof(InputAction.m_Name)).stringValue == name));
+                ?.FirstOrDefault(p => p.FindPropertyRelative(nameof(InputAction.m_Name)).stringValue == name);
+
+            // If the action is not found, return null.
+            if (property == null)
+                return null;
+            return new SerializedInputAction(property);
         }
 
         public static SerializedInputBinding GetCompositeOrBindingInMap(SerializedProperty actionMap, int bindingIndex)