FIX: Prevent composite parts being pasted into non-composites

Packages/com.unity.inputsystem/CHANGELOG.md

@@ -13,6 +13,7 @@ however, it has to be formatted properly to pass verification tests.
 ### Fixed
 - Fixed an issue where all action maps were enabled initially for project wide actions, which overrode the PlayerInput action map configuration. [ISXB-920](https://issuetracker.unity3d.com/product/unity/issues/guid/ISXB-920)
 - Fixed an issue where ButtonStates are not fully updated when switching SingleUnifiedPointer. [ISXB-1356](https://issuetracker.unity3d.com/product/unity/issues/guid/ISXB-1356)
+- Fixed errors when pasting composite parts into non-composites. [ISXB-757](https://issuetracker.unity3d.com/product/unity/issues/guid/ISXB-757)
 
 ### Changed
 - Changed enum value `Key.IMESelected` to obsolete which was not a real key. Please use the ButtonControl `imeSelected`.

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

@@ -795,6 +795,10 @@ Type CopyTagToType(string tagName)
             var itemType = CopyTagToType(tag);
             if (location.item is ActionTreeItemBase dropTarget)
             {
+                // Specific case - Composite parts cannot be dropped into Bindings
+                if (tag == k_PartOfCompositeBindingTag && location.item is not(CompositeBindingTreeItem or PartOfCompositeBindingTreeItem))
+                    return;
+
                 if (!dropTarget.GetDropLocation(itemType, location.childIndex, ref array, ref arrayIndex))
                     return;
             }

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

@@ -94,12 +94,16 @@ protected override void DrawGeneralProperties()
                     if (m_CompositeParts == null)
                         InitializeCompositePartProperties();
 
-                    var selectedPart = EditorGUILayout.Popup(s_CompositePartAssignmentLabel, m_SelectedCompositePart,
-                        m_CompositePartOptions);
-                    if (selectedPart != m_SelectedCompositePart)
+                    // If m_CompositeParts still null after InitializeCompositePartProperties something went wrong and we can't select
+                    if (m_CompositeParts != null)
                     {
-                        m_SelectedCompositePart = selectedPart;
-                        OnCompositePartAssignmentChanged();
+                        var selectedPart = EditorGUILayout.Popup(s_CompositePartAssignmentLabel, m_SelectedCompositePart,
+                            m_CompositePartOptions);
+                        if (selectedPart != m_SelectedCompositePart)
+                        {
+                            m_SelectedCompositePart = selectedPart;
+                            OnCompositePartAssignmentChanged();
+                        }
                     }
                 }
 

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

@@ -266,7 +266,8 @@ public static Command PasteActionsOrBindings(List<IPasteListener> pasteListeners
                         else
                             lastPastedElement = CopyPasteHelper.PasteActionsOrBindingsFromClipboard(state.With(selectedBindingIndex: newIndex >= 0 ? newIndex : state.selectedBindingIndex));
 
-                        lastPastedElement.FindPropertyRelative("m_Action").stringValue = relatedAction.Value.name;
+                        if (lastPastedElement != null)
+                            lastPastedElement.FindPropertyRelative("m_Action").stringValue = relatedAction.Value.name;
                     }
                 }