Fix: Retain slot name when baking action

Previously when an action was baked, the slot name was not retained.
This causes problems when switching between actions because the slot
will not automatically be assigned.

This is now fixed by ensuring that the name of the last assigned slot
is used to create the new slot.

Pull Request: https://projects.blender.org/blender/blender/pulls/136814

scripts/modules/bpy_extras/anim_utils.py

@@ -393,6 +393,7 @@ def bake_action_iter(
 
     # in case animation data hasn't been created
     atd = obj.animation_data_create()
+    old_slot_name = atd.last_slot_identifier[2:]
     is_new_action = action is None
     if is_new_action:
         action = bpy.data.actions.new("Action")
@@ -406,7 +407,7 @@ def bake_action_iter(
 
     # A slot needs to be assigned.
     if not atd.action_slot:
-        slot = action.slots.new(obj.id_type, obj.name)
+        slot = action.slots.new(obj.id_type, old_slot_name or obj.name)
         atd.action_slot = slot
 
     # Baking the action only makes sense in Replace mode, so force it (#69105)

tests/python/bl_animation_bake.py

@@ -76,6 +76,7 @@ class ObjectBakeTest(unittest.TestCase):
         self.assertNotEqual(action, self.obj.animation_data.action, "Expected baking to result in a new action")
         baked_action = self.obj.animation_data.action
         self.assertEqual(len(baked_action.slots), 1)
+        self.assertEqual(baked_action.slots[0].name_display, action.slots[0].name_display)
         channelbag = anim_utils.action_get_channelbag_for_slot(baked_action, self.obj.animation_data.action_slot)
 
         self.assertIsNotNone(channelbag)
@@ -137,12 +138,14 @@ class ObjectBakeTest(unittest.TestCase):
 
         self.assertIsNotNone(self.obj.animation_data.action_slot)
         self.assertIsNotNone(obj2.animation_data.action_slot)
-
+        self.assertNotEqual(self.obj.animation_data.action_slot, obj2.animation_data.action_slot)
+        original_slot = obj2.animation_data.action_slot
         anim_utils.bake_action_objects([(obj2, None)], frames=range(0, 10), bake_options=OBJECT_BAKE_OPTIONS)
 
         self.assertNotEqual(action, obj2.animation_data.action, "Expected baking to result in a new action")
         baked_action = obj2.animation_data.action
         self.assertEqual(len(baked_action.slots), 1)
+        self.assertEqual(original_slot.name_display, baked_action.slots[0].name_display)
         channelbag = anim_utils.action_get_channelbag_for_slot(baked_action, baked_action.slots[0])
 
         for fcurve in channelbag.fcurves: