Don't modify tied_weight_keys in-place

src/transformers/modeling_utils.py

@@ -1321,6 +1321,7 @@ def __init__(self, config: PreTrainedConfig, *inputs, **kwargs):
         # when a different component (e.g. language_model) is used.
         self._keep_in_fp32_modules = copy.copy(self.__class__._keep_in_fp32_modules)
         self._keep_in_fp32_modules_strict = copy.copy(self.__class__._keep_in_fp32_modules_strict)
+        self._tied_weights_keys = copy.copy(self.__class__._tied_weights_keys)
         self.dtype_plan = {}
 
         if isinstance(self._keep_in_fp32_modules, list):

tests/models/deformable_detr/test_modeling_deformable_detr.py

@@ -243,6 +243,25 @@ def test_deformable_detr_object_detection_head_model(self):
         config_and_inputs = self.model_tester.prepare_config_and_inputs()
         self.model_tester.create_and_check_deformable_detr_object_detection_head_model(*config_and_inputs)
 
+    def test_tie_weights_is_not_modified(self):
+        config, inputs_dict = self.model_tester.prepare_config_and_inputs_for_common()
+        config.tie_word_embeddings = True
+
+        config.with_box_refine = True
+        config.two_stage = True
+
+        model = DeformableDetrForObjectDetection(config)
+        self.assertTrue("model.decoder.bbox_embed" in model._tied_weights_keys)
+        self.assertTrue("model.decoder.class_embed" in model._tied_weights_keys)
+
+        # if we update config attr, model's tied weights keys also change
+        config.with_box_refine = False
+        config.two_stage = False
+
+        model = DeformableDetrForObjectDetection(config)
+        self.assertFalse("model.decoder.bbox_embed" in model._tied_weights_keys)
+        self.assertFalse("model.decoder.class_embed" in model._tied_weights_keys)
+
     @unittest.skip(reason="Deformable DETR does not use inputs_embeds")
     def test_inputs_embeds(self):
         pass

tests/models/grounding_dino/test_modeling_grounding_dino.py

@@ -322,6 +322,19 @@ def test_feed_forward_chunking(self):
     def test_load_save_without_tied_weights(self):
         pass
 
+    def test_tie_weights_is_not_modified(self):
+        config, inputs_dict = self.model_tester.prepare_config_and_inputs_for_common()
+        config.tie_word_embeddings = True
+
+        config.decoder_bbox_embed_share = False
+        model = GroundingDinoForObjectDetection(config)
+        self.assertFalse(r"bbox_embed.(?![0])\d+" in model._tied_weights_keys)
+
+        # if we update config attr, model's tied weights keys also change
+        config.decoder_bbox_embed_share = True
+        model = GroundingDinoForObjectDetection(config)
+        self.assertTrue(r"bbox_embed.(?![0])\d+" in model._tied_weights_keys)
+
     def test_attention_outputs(self):
         config, inputs_dict = self.model_tester.prepare_config_and_inputs_for_common()
         config.return_dict = True