update

src/diffusers/models/auto_model.py

@@ -31,10 +31,132 @@ class AutoModel(ConfigMixin):
     def __init__(self, *args, **kwargs):
         raise EnvironmentError(
             f"{self.__class__.__name__} is designed to be instantiated "
-            f"using the `{self.__class__.__name__}.from_pretrained(pretrained_model_name_or_path)` or "
+            f"using the `{self.__class__.__name__}.from_pretrained(pretrained_model_name_or_path)`, "
+            f"`{self.__class__.__name__}.from_config(config)`, or "
             f"`{self.__class__.__name__}.from_pipe(pipeline)` methods."
         )
 
+    @classmethod
+    def from_config(
+        cls, pretrained_model_name_or_path_or_dict: Optional[Union[str, os.PathLike, dict]] = None, **kwargs
+    ):
+        r"""
+        Instantiate a model from a config dictionary or a pretrained model configuration file with random weights (no
+        pretrained weights are loaded).
+
+        Parameters:
+            pretrained_model_name_or_path_or_dict (`str`, `os.PathLike`, or `dict`):
+                Can be either:
+
+                    - A string, the *model id* (for example `google/ddpm-celebahq-256`) of a pretrained model
+                      configuration hosted on the Hub.
+                    - A path to a *directory* (for example `./my_model_directory`) containing a model configuration
+                      file.
+                    - A config dictionary.
+
+            cache_dir (`Union[str, os.PathLike]`, *optional*):
+                Path to a directory where a downloaded pretrained model configuration is cached if the standard cache
+                is not used.
+            force_download (`bool`, *optional*, defaults to `False`):
+                Whether or not to force the (re-)download of the model configuration, overriding the cached version if
+                it exists.
+            proxies (`Dict[str, str]`, *optional*):
+                A dictionary of proxy servers to use by protocol or endpoint.
+            local_files_only(`bool`, *optional*, defaults to `False`):
+                Whether to only load local model configuration files or not.
+            token (`str` or *bool*, *optional*):
+                The token to use as HTTP bearer authorization for remote files.
+            revision (`str`, *optional*, defaults to `"main"`):
+                The specific model version to use.
+            trust_remote_code (`bool`, *optional*, defaults to `False`):
+                Whether to trust remote code.
+            subfolder (`str`, *optional*, defaults to `""`):
+                The subfolder location of a model file within a larger model repository on the Hub or locally.
+
+        Returns:
+            A model object instantiated from the config with random weights.
+
+        Example:
+
+        ```py
+        from diffusers import AutoModel
+
+        model = AutoModel.from_config("stable-diffusion-v1-5/stable-diffusion-v1-5", subfolder="unet")
+        ```
+        """
+        subfolder = kwargs.pop("subfolder", None)
+        trust_remote_code = kwargs.pop("trust_remote_code", False)
+
+        hub_kwargs_names = [
+            "cache_dir",
+            "force_download",
+            "local_files_only",
+            "proxies",
+            "revision",
+            "token",
+        ]
+        hub_kwargs = {name: kwargs.pop(name, None) for name in hub_kwargs_names}
+
+        if pretrained_model_name_or_path_or_dict is None:
+            raise ValueError(
+                "Please provide a `pretrained_model_name_or_path_or_dict` as the first positional argument."
+            )
+
+        if isinstance(pretrained_model_name_or_path_or_dict, (str, os.PathLike)):
+            pretrained_model_name_or_path = pretrained_model_name_or_path_or_dict
+            cls.config_name = "config.json"
+            config = cls.load_config(pretrained_model_name_or_path, subfolder=subfolder, **hub_kwargs)
+        else:
+            config = pretrained_model_name_or_path_or_dict
+            pretrained_model_name_or_path = config.get("_name_or_path")
+
+        library = None
+        orig_class_name = None
+
+        if "_class_name" in config:
+            orig_class_name = config["_class_name"]
+            library = "diffusers"
+        elif "model_type" in config:
+            orig_class_name = "AutoModel"
+            library = "transformers"
+        else:
+            raise ValueError(
+                f"Couldn't find a model class associated with the config: {config}. Make sure the config "
+                "contains a `_class_name` or `model_type` key."
+            )
+
+        has_remote_code = "auto_map" in config and cls.__name__ in config["auto_map"]
+        trust_remote_code = resolve_trust_remote_code(
+            trust_remote_code, pretrained_model_name_or_path, has_remote_code
+        )
+
+        if has_remote_code and trust_remote_code:
+            class_ref = config["auto_map"][cls.__name__]
+            module_file, class_name = class_ref.split(".")
+            module_file = module_file + ".py"
+            model_cls = get_class_from_dynamic_module(
+                pretrained_model_name_or_path,
+                subfolder=subfolder,
+                module_file=module_file,
+                class_name=class_name,
+                **hub_kwargs,
+            )
+        else:
+            from ..pipelines.pipeline_loading_utils import ALL_IMPORTABLE_CLASSES, get_class_obj_and_candidates
+
+            model_cls, _ = get_class_obj_and_candidates(
+                library_name=library,
+                class_name=orig_class_name,
+                importable_classes=ALL_IMPORTABLE_CLASSES,
+                pipelines=None,
+                is_pipeline_module=False,
+            )
+
+        if model_cls is None:
+            raise ValueError(f"AutoModel can't find a model linked to {orig_class_name}.")
+
+        return model_cls.from_config(config, **kwargs)
+
     @classmethod
     @validate_hf_hub_args
     def from_pretrained(cls, pretrained_model_or_path: Optional[Union[str, os.PathLike]] = None, **kwargs):

tests/models/test_models_auto.py

@@ -1,5 +1,5 @@
 import unittest
-from unittest.mock import patch
+from unittest.mock import MagicMock, patch
 
 from transformers import CLIPTextModel, LongformerModel
 
@@ -30,3 +30,69 @@ class TestAutoModel(unittest.TestCase):
     def test_load_from_model_index(self):
         model = AutoModel.from_pretrained("hf-internal-testing/tiny-stable-diffusion-torch", subfolder="text_encoder")
         assert isinstance(model, CLIPTextModel)
+
+
+class TestAutoModelFromConfig(unittest.TestCase):
+    @patch(
+        "diffusers.pipelines.pipeline_loading_utils.get_class_obj_and_candidates",
+        return_value=(MagicMock(), None),
+    )
+    def test_from_config_with_dict_diffusers_class(self, mock_get_class):
+        config = {"_class_name": "UNet2DConditionModel", "sample_size": 64}
+        mock_model = MagicMock()
+        mock_get_class.return_value[0].from_config.return_value = mock_model
+
+        result = AutoModel.from_config(config)
+
+        mock_get_class.assert_called_once_with(
+            library_name="diffusers",
+            class_name="UNet2DConditionModel",
+            importable_classes=unittest.mock.ANY,
+            pipelines=None,
+            is_pipeline_module=False,
+        )
+        mock_get_class.return_value[0].from_config.assert_called_once_with(config)
+        assert result is mock_model
+
+    @patch(
+        "diffusers.pipelines.pipeline_loading_utils.get_class_obj_and_candidates",
+        return_value=(MagicMock(), None),
+    )
+    @patch("diffusers.models.AutoModel.load_config", return_value={"_class_name": "UNet2DConditionModel"})
+    def test_from_config_with_string_path(self, mock_load_config, mock_get_class):
+        mock_model = MagicMock()
+        mock_get_class.return_value[0].from_config.return_value = mock_model
+
+        result = AutoModel.from_config("hf-internal-testing/tiny-stable-diffusion-torch", subfolder="unet")
+
+        mock_load_config.assert_called_once()
+        assert result is mock_model
+
+    def test_from_config_raises_on_missing_class_info(self):
+        config = {"some_key": "some_value"}
+        with self.assertRaises(ValueError, msg="Couldn't find a model class"):
+            AutoModel.from_config(config)
+
+    @patch(
+        "diffusers.pipelines.pipeline_loading_utils.get_class_obj_and_candidates",
+        return_value=(MagicMock(), None),
+    )
+    def test_from_config_with_model_type_routes_to_transformers(self, mock_get_class):
+        config = {"model_type": "clip_text_model"}
+        mock_model = MagicMock()
+        mock_get_class.return_value[0].from_config.return_value = mock_model
+
+        result = AutoModel.from_config(config)
+
+        mock_get_class.assert_called_once_with(
+            library_name="transformers",
+            class_name="AutoModel",
+            importable_classes=unittest.mock.ANY,
+            pipelines=None,
+            is_pipeline_module=False,
+        )
+        assert result is mock_model
+
+    def test_from_config_raises_on_none(self):
+        with self.assertRaises(ValueError, msg="Please provide a `pretrained_model_name_or_path_or_dict`"):
+            AutoModel.from_config(None)