Allow generic composite models to pass more kwargs (#24927)

* fix

* Update src/transformers/generation/utils.py

Co-authored-by: Joao Gante <joaofranciscocardosogante@gmail.com>

* update

---------

Co-authored-by: ydshieh <ydshieh@users.noreply.github.com>
Co-authored-by: Joao Gante <joaofranciscocardosogante@gmail.com>

src/transformers/generation/utils.py

@@ -1147,6 +1147,27 @@ class GenerationMixin:
         # `prepare_inputs_for_generation` doesn't accept them, then a stricter check can be made ;)
         if "kwargs" in model_args or "model_kwargs" in model_args:
             model_args |= set(inspect.signature(self.forward).parameters)
+
+        # Encoder-Decoder models may also need Encoder arguments from `model_kwargs`
+        if self.config.is_encoder_decoder:
+            base_model = getattr(self, self.base_model_prefix, None)
+
+            # allow encoder kwargs
+            encoder = getattr(self, "encoder", None)
+            if encoder is None:
+                encoder = getattr(base_model, "encoder")
+
+            encoder_model_args = set(inspect.signature(encoder.forward).parameters)
+            model_args |= encoder_model_args
+
+            # allow decoder kwargs
+            decoder = getattr(self, "decoder", None)
+            if decoder is None:
+                decoder = getattr(base_model, "decoder")
+
+            decoder_model_args = set(inspect.signature(decoder.forward).parameters)
+            model_args |= {f"decoder_{x}" for x in decoder_model_args}
+
         for key, value in model_kwargs.items():
             if value is not None and key not in model_args:
                 unused_model_args.append(key)