[Modular] Updates for Custom Pipeline Blocks (#11940)

* update

* update

* update

src/diffusers/modular_pipelines/modular_pipeline.py

@@ -323,6 +323,7 @@ class ModularPipelineBlocks(ConfigMixin, PushToHubMixin):
     """
 
     config_name = "config.json"
+    model_name = None
 
     @classmethod
     def _get_signature_keys(cls, obj):
@@ -333,6 +334,14 @@ class ModularPipelineBlocks(ConfigMixin, PushToHubMixin):
 
         return expected_modules, optional_parameters
 
+    @property
+    def expected_components(self) -> List[ComponentSpec]:
+        return []
+
+    @property
+    def expected_configs(self) -> List[ConfigSpec]:
+        return []
+
     @classmethod
     def from_pretrained(
         cls,
@@ -358,7 +367,9 @@ class ModularPipelineBlocks(ConfigMixin, PushToHubMixin):
             trust_remote_code, pretrained_model_name_or_path, has_remote_code
         )
         if not (has_remote_code and trust_remote_code):
-            raise ValueError("TODO")
+            raise ValueError(
+                "Selected model repository does not happear to have any custom code or does not have a valid `config.json` file."
+            )
 
         class_ref = config["auto_map"][cls.__name__]
         module_file, class_name = class_ref.split(".")
@@ -367,7 +378,6 @@ class ModularPipelineBlocks(ConfigMixin, PushToHubMixin):
             pretrained_model_name_or_path,
             module_file=module_file,
             class_name=class_name,
-            is_modular=True,
             **hub_kwargs,
             **kwargs,
         )

src/diffusers/modular_pipelines/modular_pipeline_utils.py

@@ -93,7 +93,7 @@ class ComponentSpec:
     config: Optional[FrozenDict] = None
     # YiYi Notes: should we change it to pretrained_model_name_or_path for consistency? a bit long for a field name
     repo: Optional[Union[str, List[str]]] = field(default=None, metadata={"loading": True})
-    subfolder: Optional[str] = field(default=None, metadata={"loading": True})
+    subfolder: Optional[str] = field(default="", metadata={"loading": True})
     variant: Optional[str] = field(default=None, metadata={"loading": True})
     revision: Optional[str] = field(default=None, metadata={"loading": True})
     default_creation_method: Literal["from_config", "from_pretrained"] = "from_pretrained"