[Dummy imports] Better error message

src/diffusers/pipeline_utils.py

@@ -49,6 +49,7 @@
 
 INDEX_FILE = "diffusion_pytorch_model.bin"
 CUSTOM_PIPELINE_FILE_NAME = "pipeline.py"
+DUMMY_MODULES_FOLDER = "diffusers.utils"
 
 
 logger = logging.get_logger(__name__)
@@ -467,9 +468,20 @@ def from_pretrained(cls, pretrained_model_name_or_path: Optional[Union[str, os.P
                     if issubclass(class_obj, class_candidate):
                         load_method_name = importable_classes[class_name][1]
 
-                load_method = getattr(class_obj, load_method_name)
+                if load_method_name is None:
+                    none_module = class_obj.__module__
+                    if none_module.startswith(DUMMY_MODULES_FOLDER) and "dummy" in none_module:
+                        # call class_obj for nice error message of missing requirements
+                        class_obj()
+
+                    raise ValueError(
+                        f"The component {class_obj} of {pipeline_class} cannot be loaded as it does not seem to have"
+                        f" any of the loading methods defined in {ALL_IMPORTABLE_CLASSES}."
+                    )
 
+                load_method = getattr(class_obj, load_method_name)
                 loading_kwargs = {}
+
                 if issubclass(class_obj, torch.nn.Module):
                     loading_kwargs["torch_dtype"] = torch_dtype
                 if issubclass(class_obj, diffusers.OnnxRuntimeModel):

src/diffusers/utils/dummy_flax_and_transformers_objects.py

@@ -9,3 +9,11 @@ class FlaxStableDiffusionPipeline(metaclass=DummyObject):
 
     def __init__(self, *args, **kwargs):
         requires_backends(self, ["flax", "transformers"])
+
+    @classmethod
+    def from_config(cls, *args, **kwargs):
+        requires_backends(cls, ["flax", "transformers"])
+
+    @classmethod
+    def from_pretrained(cls, *args, **kwargs):
+        requires_backends(cls, ["flax", "transformers"])

src/diffusers/utils/dummy_flax_objects.py

@@ -10,72 +10,160 @@ class FlaxModelMixin(metaclass=DummyObject):
     def __init__(self, *args, **kwargs):
         requires_backends(self, ["flax"])
 
+    @classmethod
+    def from_config(cls, *args, **kwargs):
+        requires_backends(cls, ["flax"])
+
+    @classmethod
+    def from_pretrained(cls, *args, **kwargs):
+        requires_backends(cls, ["flax"])
+
 
 class FlaxUNet2DConditionModel(metaclass=DummyObject):
     _backends = ["flax"]
 
     def __init__(self, *args, **kwargs):
         requires_backends(self, ["flax"])
 
+    @classmethod
+    def from_config(cls, *args, **kwargs):
+        requires_backends(cls, ["flax"])
+
+    @classmethod
+    def from_pretrained(cls, *args, **kwargs):
+        requires_backends(cls, ["flax"])
+
 
 class FlaxAutoencoderKL(metaclass=DummyObject):
     _backends = ["flax"]
 
     def __init__(self, *args, **kwargs):
         requires_backends(self, ["flax"])
 
+    @classmethod
+    def from_config(cls, *args, **kwargs):
+        requires_backends(cls, ["flax"])
+
+    @classmethod
+    def from_pretrained(cls, *args, **kwargs):
+        requires_backends(cls, ["flax"])
+
 
 class FlaxDiffusionPipeline(metaclass=DummyObject):
     _backends = ["flax"]
 
     def __init__(self, *args, **kwargs):
         requires_backends(self, ["flax"])
 
+    @classmethod
+    def from_config(cls, *args, **kwargs):
+        requires_backends(cls, ["flax"])
+
+    @classmethod
+    def from_pretrained(cls, *args, **kwargs):
+        requires_backends(cls, ["flax"])
+
 
 class FlaxDDIMScheduler(metaclass=DummyObject):
     _backends = ["flax"]
 
     def __init__(self, *args, **kwargs):
         requires_backends(self, ["flax"])
 
+    @classmethod
+    def from_config(cls, *args, **kwargs):
+        requires_backends(cls, ["flax"])
+
+    @classmethod
+    def from_pretrained(cls, *args, **kwargs):
+        requires_backends(cls, ["flax"])
+
 
 class FlaxDDPMScheduler(metaclass=DummyObject):
     _backends = ["flax"]
 
     def __init__(self, *args, **kwargs):
         requires_backends(self, ["flax"])
 
+    @classmethod
+    def from_config(cls, *args, **kwargs):
+        requires_backends(cls, ["flax"])
+
+    @classmethod
+    def from_pretrained(cls, *args, **kwargs):
+        requires_backends(cls, ["flax"])
+
 
 class FlaxKarrasVeScheduler(metaclass=DummyObject):
     _backends = ["flax"]
 
     def __init__(self, *args, **kwargs):
         requires_backends(self, ["flax"])
 
+    @classmethod
+    def from_config(cls, *args, **kwargs):
+        requires_backends(cls, ["flax"])
+
+    @classmethod
+    def from_pretrained(cls, *args, **kwargs):
+        requires_backends(cls, ["flax"])
+
 
 class FlaxLMSDiscreteScheduler(metaclass=DummyObject):
     _backends = ["flax"]
 
     def __init__(self, *args, **kwargs):
         requires_backends(self, ["flax"])
 
+    @classmethod
+    def from_config(cls, *args, **kwargs):
+        requires_backends(cls, ["flax"])
+
+    @classmethod
+    def from_pretrained(cls, *args, **kwargs):
+        requires_backends(cls, ["flax"])
+
 
 class FlaxPNDMScheduler(metaclass=DummyObject):
     _backends = ["flax"]
 
     def __init__(self, *args, **kwargs):
         requires_backends(self, ["flax"])
 
+    @classmethod
+    def from_config(cls, *args, **kwargs):
+        requires_backends(cls, ["flax"])
+
+    @classmethod
+    def from_pretrained(cls, *args, **kwargs):
+        requires_backends(cls, ["flax"])
+
 
 class FlaxSchedulerMixin(metaclass=DummyObject):
     _backends = ["flax"]
 
     def __init__(self, *args, **kwargs):
         requires_backends(self, ["flax"])
 
+    @classmethod
+    def from_config(cls, *args, **kwargs):
+        requires_backends(cls, ["flax"])
+
+    @classmethod
+    def from_pretrained(cls, *args, **kwargs):
+        requires_backends(cls, ["flax"])
+
 
 class FlaxScoreSdeVeScheduler(metaclass=DummyObject):
     _backends = ["flax"]
 
     def __init__(self, *args, **kwargs):
         requires_backends(self, ["flax"])
+
+    @classmethod
+    def from_config(cls, *args, **kwargs):
+        requires_backends(cls, ["flax"])
+
+    @classmethod
+    def from_pretrained(cls, *args, **kwargs):
+        requires_backends(cls, ["flax"])