[LoRA] minor fix for `load_lora_weights()` for Flux and a test (#11595)

* fix peft delete adapters for flux.

* add test

* empty commit

src/diffusers/loaders/lora_pipeline.py

@@ -2545,14 +2545,13 @@ class FluxLoraLoaderMixin(LoraBaseMixin):
         if unexpected_modules:
             logger.debug(f"Found unexpected modules: {unexpected_modules}. These will be ignored.")
 
-        is_peft_loaded = getattr(transformer, "peft_config", None) is not None
         for k in lora_module_names:
             if k in unexpected_modules:
                 continue
 
             base_param_name = (
                 f"{k.replace(prefix, '')}.base_layer.weight"
-                if is_peft_loaded and f"{k.replace(prefix, '')}.base_layer.weight" in transformer_state_dict
+                if f"{k.replace(prefix, '')}.base_layer.weight" in transformer_state_dict
                 else f"{k.replace(prefix, '')}.weight"
             )
             base_weight_param = transformer_state_dict[base_param_name]

tests/lora/utils.py

@@ -2149,3 +2149,51 @@ class PeftLoraLoaderMixinTests:
 
             _, _, inputs = self.get_dummy_inputs(with_generator=False)
             pipe(**inputs, generator=torch.manual_seed(0))[0]
+
+    def test_inference_load_delete_load_adapters(self):
+        "Tests if `load_lora_weights()` -> `delete_adapters()` -> `load_lora_weights()` works."
+        for scheduler_cls in self.scheduler_classes:
+            components, text_lora_config, denoiser_lora_config = self.get_dummy_components(scheduler_cls)
+            pipe = self.pipeline_class(**components)
+            pipe = pipe.to(torch_device)
+            pipe.set_progress_bar_config(disable=None)
+            _, _, inputs = self.get_dummy_inputs(with_generator=False)
+
+            output_no_lora = pipe(**inputs, generator=torch.manual_seed(0))[0]
+
+            if "text_encoder" in self.pipeline_class._lora_loadable_modules:
+                pipe.text_encoder.add_adapter(text_lora_config)
+                self.assertTrue(
+                    check_if_lora_correctly_set(pipe.text_encoder), "Lora not correctly set in text encoder"
+                )
+
+            denoiser = pipe.transformer if self.unet_kwargs is None else pipe.unet
+            denoiser.add_adapter(denoiser_lora_config)
+            self.assertTrue(check_if_lora_correctly_set(denoiser), "Lora not correctly set in denoiser.")
+
+            if self.has_two_text_encoders or self.has_three_text_encoders:
+                lora_loadable_components = self.pipeline_class._lora_loadable_modules
+                if "text_encoder_2" in lora_loadable_components:
+                    pipe.text_encoder_2.add_adapter(text_lora_config)
+                    self.assertTrue(
+                        check_if_lora_correctly_set(pipe.text_encoder_2), "Lora not correctly set in text encoder 2"
+                    )
+
+            output_adapter_1 = pipe(**inputs, generator=torch.manual_seed(0))[0]
+
+            with tempfile.TemporaryDirectory() as tmpdirname:
+                modules_to_save = self._get_modules_to_save(pipe, has_denoiser=True)
+                lora_state_dicts = self._get_lora_state_dicts(modules_to_save)
+                self.pipeline_class.save_lora_weights(save_directory=tmpdirname, **lora_state_dicts)
+                self.assertTrue(os.path.isfile(os.path.join(tmpdirname, "pytorch_lora_weights.safetensors")))
+
+                # First, delete adapter and compare.
+                pipe.delete_adapters(pipe.get_active_adapters()[0])
+                output_no_adapter = pipe(**inputs, generator=torch.manual_seed(0))[0]
+                self.assertFalse(np.allclose(output_adapter_1, output_no_adapter, atol=1e-3, rtol=1e-3))
+                self.assertTrue(np.allclose(output_no_lora, output_no_adapter, atol=1e-3, rtol=1e-3))
+
+                # Then load adapter and compare.
+                pipe.load_lora_weights(tmpdirname)
+                output_lora_loaded = pipe(**inputs, generator=torch.manual_seed(0))[0]
+                self.assertTrue(np.allclose(output_adapter_1, output_lora_loaded, atol=1e-3, rtol=1e-3))