update data collator swap logic (?)

Author: djsaunde

unsloth_zoo/dataset_utils.py

@@ -364,8 +364,12 @@ def _train_on_responses_only(examples):
 
     # Edit data collator as well if not DataCollatorForSeq2Seq
     from transformers import DataCollatorForSeq2Seq
-    if hasattr(trainer, "data_collator") and \
-        not isinstance(trainer.data_collator, DataCollatorForSeq2Seq):
+    packing_enabled = getattr(trainer.args, "packing", False)
+    if (
+        hasattr(trainer, "data_collator")
+        and not isinstance(trainer.data_collator, DataCollatorForSeq2Seq)
+        and not packing_enabled
+    ):
         trainer.data_collator = DataCollatorForSeq2Seq(tokenizer = tokenizer)
 
     # Check if all labels randomnly got masked to nothing - maybe wrong chat template?