Donut: fix `generate` call from local path (#31470)

* local donut path fix

* engrish

* Update src/transformers/generation/utils.py
Co-authored-by: amyeroberts <22614925+amyeroberts@users.noreply.github.com>

---------
Co-authored-by: amyeroberts <22614925+amyeroberts@users.noreply.github.com>

src/transformers/generation/utils.py

@@ -575,8 +575,12 @@ class GenerationMixin:
         # no user input -> use decoder_start_token_id as decoder_input_ids
         if decoder_input_ids is None:
             decoder_input_ids = decoder_start_token_id
-        # exception: Donut checkpoints have task-specific decoder starts and don't expect a BOS token
-        elif self.config.model_type == "vision-encoder-decoder" and "donut" in self.name_or_path.lower():
+        # exception: Donut checkpoints have task-specific decoder starts and don't expect a BOS token. Note that the
+        # original checkpoints can't be detected through `self.__class__.__name__.lower()`, needing custom logic.
+        # See: https://github.com/huggingface/transformers/pull/31470
+        elif "donut" in self.__class__.__name__.lower() or (
+            self.config.model_type == "vision-encoder-decoder" and "donut" in self.config.encoder.model_type.lower()
+        ):
             pass
         elif self.config.model_type in ["whisper"]:
             pass