fix(api): prevent moving a labware onto itself (#16600)

Fixes bug where you could move a labware onto itself, causing a recursion error later in the protocol

api/src/opentrons/protocol_engine/commands/move_labware.py

@@ -186,6 +186,10 @@ async def execute(self, params: MoveLabwareParams) -> _ExecuteReturn:  # noqa: C
                 top_labware_definition=current_labware_definition,
                 bottom_labware_id=available_new_location.labwareId,
             )
+            if params.labwareId == available_new_location.labwareId:
+                raise LabwareMovementNotAllowedError(
+                    "Cannot move a labware onto itself."
+                )
 
         # Allow propagation of ModuleNotLoadedError.
         new_offset_id = self._equipment.find_applicable_labware_offset_id(

api/tests/opentrons/protocol_engine/commands/test_move_labware.py

@@ -803,3 +803,38 @@ async def test_move_labware_raises_when_moving_fixed_trash_labware(
         match="Cannot move fixed trash labware 'My cool labware'.",
     ):
         await subject.execute(data)
+
+
+async def test_labware_raises_when_moved_onto_itself(
+    decoy: Decoy,
+    subject: MoveLabwareImplementation,
+    state_view: StateView,
+) -> None:
+    """It should raise when the OnLabwareLocation has the same labware ID as the labware being moved."""
+    data = MoveLabwareParams(
+        labwareId="the-same-labware-id",
+        newLocation=OnLabwareLocation(labwareId="a-cool-labware-id"),
+        strategy=LabwareMovementStrategy.MANUAL_MOVE_WITH_PAUSE,
+    )
+
+    decoy.when(state_view.labware.get(labware_id="the-same-labware-id")).then_return(
+        LoadedLabware(
+            id="the-same-labware-id",
+            loadName="load-name",
+            definitionUri="opentrons-test/load-name/1",
+            location=DeckSlotLocation(slotName=DeckSlotName.SLOT_4),
+            offsetId=None,
+        )
+    )
+
+    decoy.when(
+        state_view.geometry.ensure_location_not_occupied(
+            location=OnLabwareLocation(labwareId="a-cool-labware-id"),
+        )
+    ).then_return(OnLabwareLocation(labwareId="the-same-labware-id"))
+
+    with pytest.raises(
+        errors.LabwareMovementNotAllowedError,
+        match="Cannot move a labware onto itself.",
+    ):
+        await subject.execute(data)