FIX: Duplicating multiple items in action editor creating too many duplicates.

Packages/com.unity.inputsystem/CHANGELOG.md

@@ -26,6 +26,7 @@ however, it has to be formatted properly to pass verification tests.
 - Fixed "Create Actions..." on `PlayerInput` creating an asset with an incorrect binding for taps on Touchscreens. \
   __NOTE: If you have already created an .inputactions asset with this mechanism, update "tap [Touchscreen]" to "Primary Touch/Tap" to fix the problem manually.__
 - Fixed `Invoke CSharp Events` when selected in `PlayerInput` not triggering `PlayerInput.onActionTriggered`.
+- Fixed duplicating multiple items at the same time in the action editor duplicating them repeatedly.
 
 ### Changed
 

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

@@ -550,9 +550,7 @@ public void HandleCopyPasteCommandEvent(Event uiEvent)
                         DeleteDataOfSelectedItems();
                         break;
                     case k_DuplicateCommand:
-                        var buffer = new StringBuilder();
-                        CopySelectedItemsTo(buffer);
-                        PasteDataFrom(buffer.ToString());
+                        DuplicateSelection();
                         break;
                     case k_DeleteCommand:
                         DeleteDataOfSelectedItems();
@@ -564,6 +562,38 @@ public void HandleCopyPasteCommandEvent(Event uiEvent)
             }
         }
 
+        private void DuplicateSelection()
+        {
+            var buffer = new StringBuilder();
+
+            // If we have a multi-selection, we want to perform the duplication as if each item
+            // was duplicated individually. Meaning we paste each duplicate right after the item
+            // it was duplicated from. So if, say, an action is selected at the beginning of the
+            // tree and one is selected from the end of it, we still paste the copies into the
+            // two separate locations correctly.
+            //
+            // Technically, if both parents and children are selected, we're order dependent here
+            // but not sure we really need to care.
+
+            var selection = GetSelection();
+            ClearSelection();
+
+            // Copy-paste each selected item in turn.
+            var newItemIds = new List<int>();
+            foreach (var id in selection)
+            {
+                SetSelection(new[] { id });
+
+                buffer.Length = 0;
+                CopySelectedItemsTo(buffer);
+                PasteDataFrom(buffer.ToString());
+
+                newItemIds.AddRange(GetSelection());
+            }
+
+            SetSelection(newItemIds);
+        }
+
         internal const string k_CopyPasteMarker = "INPUTASSET ";
         private const string k_StartOfText = "\u0002";
         private const string k_StartOfHeading = "\u0001";
@@ -865,11 +895,7 @@ public void BuildContextMenuFor(Type itemType, GenericMenu menu, bool multiSelec
             {
                 menu.AddDisabledItem(s_RenameLabel);
             }
-            menu.AddItem(s_DuplicateLabel, false, () =>
-            {
-                CopySelectedItemsToClipboard();
-                PasteDataFromClipboard();
-            });
+            menu.AddItem(s_DuplicateLabel, false, DuplicateSelection);
             menu.AddItem(s_DeleteLabel, false, DeleteDataOfSelectedItems);
         }