Allow passing non-default modules to pipeline (#188)

* Allow passing non-default modules to pipeline.

Override modules are recognized and replaced in the pipeline. However,
no check is performed about mismatched classes yet. This is because the
override module is already instantiated and we have no library or class
name to compare against.

* up

* add test

Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>

src/diffusers/pipeline_utils.py

@@ -15,6 +15,7 @@
 # limitations under the License.
 
 import importlib
+import inspect
 import os
 from typing import Optional, Union
 
@@ -148,6 +149,12 @@ class DiffusionPipeline(ConfigMixin):
             diffusers_module = importlib.import_module(cls.__module__.split(".")[0])
             pipeline_class = getattr(diffusers_module, config_dict["_class_name"])
 
+        # some modules can be passed directly to the init
+        # in this case they are already instantiated in `kwargs`
+        # extract them here
+        expected_modules = set(inspect.signature(pipeline_class.__init__).parameters.keys())
+        passed_class_obj = {k: kwargs.pop(k) for k in expected_modules if k in kwargs}
+
         init_dict, _ = pipeline_class.extract_init_dict(config_dict, **kwargs)
 
         init_kwargs = {}
@@ -158,8 +165,36 @@ class DiffusionPipeline(ConfigMixin):
         # 3. Load each module in the pipeline
         for name, (library_name, class_name) in init_dict.items():
             is_pipeline_module = hasattr(pipelines, library_name)
+            loaded_sub_model = None
+
             # if the model is in a pipeline module, then we load it from the pipeline
-            if is_pipeline_module:
+            if name in passed_class_obj:
+                # 1. check that passed_class_obj has correct parent class
+                if not is_pipeline_module:
+                    library = importlib.import_module(library_name)
+                    class_obj = getattr(library, class_name)
+                    importable_classes = LOADABLE_CLASSES[library_name]
+                    class_candidates = {c: getattr(library, c) for c in importable_classes.keys()}
+
+                    expected_class_obj = None
+                    for class_name, class_candidate in class_candidates.items():
+                        if issubclass(class_obj, class_candidate):
+                            expected_class_obj = class_candidate
+
+                    if not issubclass(passed_class_obj[name].__class__, expected_class_obj):
+                        raise ValueError(
+                            f"{passed_class_obj[name]} is of type: {type(passed_class_obj[name])}, but should be"
+                            f" {expected_class_obj}"
+                        )
+                else:
+                    logger.warn(
+                        f"You have passed a non-standard module {passed_class_obj[name]}. We cannot verify whether it"
+                        " has the correct type"
+                    )
+
+                # set passed class object
+                loaded_sub_model = passed_class_obj[name]
+            elif is_pipeline_module:
                 pipeline_module = getattr(pipelines, library_name)
                 class_obj = getattr(pipeline_module, class_name)
                 importable_classes = ALL_IMPORTABLE_CLASSES
@@ -171,6 +206,7 @@ class DiffusionPipeline(ConfigMixin):
                 importable_classes = LOADABLE_CLASSES[library_name]
                 class_candidates = {c: getattr(library, c) for c in importable_classes.keys()}
 
+            if loaded_sub_model is None:
                 load_method_name = None
                 for class_name, class_candidate in class_candidates.items():
                     if issubclass(class_obj, class_candidate):
@@ -187,7 +223,7 @@ class DiffusionPipeline(ConfigMixin):
 
             init_kwargs[name] = loaded_sub_model  # UNet(...), # DiffusionSchedule(...)
 
-        # 5. Instantiate the pipeline
+        # 4. Instantiate the pipeline
         model = pipeline_class(**init_kwargs)
         return model
 

tests/test_modeling_utils.py

@@ -718,6 +718,28 @@ class PipelineTesterMixin(unittest.TestCase):
 
         assert np.abs(image - new_image).sum() < 1e-5, "Models don't give the same forward pass"
 
+    @slow
+    def test_from_pretrained_hub_pass_model(self):
+        model_path = "google/ddpm-cifar10-32"
+
+        # pass unet into DiffusionPipeline
+        unet = UNet2DModel.from_pretrained(model_path)
+        ddpm_from_hub_custom_model = DDPMPipeline.from_pretrained(model_path, unet=unet)
+        ddpm_from_hub_custom_model = DiffusionPipeline.from_pretrained(model_path, unet=unet)
+
+        ddpm_from_hub = DiffusionPipeline.from_pretrained(model_path)
+
+        ddpm_from_hub_custom_model.scheduler.num_timesteps = 10
+        ddpm_from_hub.scheduler.num_timesteps = 10
+
+        generator = torch.manual_seed(0)
+
+        image = ddpm_from_hub_custom_model(generator=generator, output_type="numpy")["sample"]
+        generator = generator.manual_seed(0)
+        new_image = ddpm_from_hub(generator=generator, output_type="numpy")["sample"]
+
+        assert np.abs(image - new_image).sum() < 1e-5, "Models don't give the same forward pass"
+
     @slow
     def test_output_format(self):
         model_path = "google/ddpm-cifar10-32"