FIX Warning abt config.json when the base model is local. (#1668)

Fix incorrect warning when loading local model.

src/peft/utils/save_and_load.py

@@ -185,25 +185,26 @@ def get_peft_model_state_dict(
 
         # For some models e.g. diffusers the text config file is stored in a subfolder
         # we need to make sure we can download that config.
-        has_remote_config = False
+        has_base_config = False
 
         # ensure that this check is not performed in HF offline mode, see #1452
         if model_id is not None:
-            exists = check_file_exists_on_hf_hub(model_id, "config.json")
+            local_config_exists = os.path.exists(os.path.join(model_id, "config.json"))
+            exists = local_config_exists or check_file_exists_on_hf_hub(model_id, "config.json")
             if exists is None:
                 # check failed, could not determine if it exists or not
                 warnings.warn(
                     f"Could not find a config file in {model_id} - will assume that the vocabulary was not modified."
                 )
-                has_remote_config = False
+                has_base_config = False
             else:
-                has_remote_config = exists
+                has_base_config = exists
 
         # check if the vocab size of the base model is different from the vocab size of the finetuned model
         if (
             vocab_size
             and model_id
-            and has_remote_config
+            and has_base_config
             and (vocab_size != model.config.__class__.from_pretrained(model_id).vocab_size)
         ):
             warnings.warn(

tests/test_hub_features.py

@@ -39,6 +39,28 @@ def test_subfolder(self):
             assert isinstance(model, PeftModel)
 
 
+class TestLocalModel:
+    def test_local_model_saving_no_warning(self, recwarn, tmp_path):
+        # When the model is saved, the library checks for vocab changes by
+        # examining `config.json` in the model path.
+        # However, previously, those checks only covered huggingface hub models.
+        # This test makes sure that the local `config.json` is checked as well.
+        # If `save_pretrained` could not find the file, it will issue a warning.
+        model_id = "facebook/opt-125m"
+        model = AutoModelForCausalLM.from_pretrained(model_id)
+        local_dir = tmp_path / model_id
+        model.save_pretrained(local_dir)
+        del model
+
+        base_model = AutoModelForCausalLM.from_pretrained(local_dir)
+        peft_config = LoraConfig()
+        peft_model = get_peft_model(base_model, peft_config)
+        peft_model.save_pretrained(local_dir)
+
+        for warning in recwarn.list:
+            assert "Could not find a config file" not in warning.message.args[0]
+
+
 class TestBaseModelRevision:
     def test_save_and_load_base_model_revision(self, tmp_path):
         r"""