automatically set pad_to_sequence_len when use packing (#2607)

* automatically set pad_to_sequence_len when use packing

* update tests

src/axolotl/utils/schemas/config.py

@@ -512,10 +512,17 @@ class AxolotlInputConfig(
     @model_validator(mode="before")
     @classmethod
     def hint_sample_packing_padding(cls, data):
-        if data.get("sample_packing") and not data.get("pad_to_sequence_len"):
-            LOG.warning(
-                "`pad_to_sequence_len: true` is recommended when using sample_packing"
-            )
+        if data.get("sample_packing"):
+            pad_to_sequence_len = data.get("pad_to_sequence_len")
+            if pad_to_sequence_len is False:
+                LOG.warning(
+                    "`pad_to_sequence_len: true` is recommended when using sample_packing"
+                )
+            elif pad_to_sequence_len is None:
+                LOG.info(
+                    "Setting `pad_to_sequence_len: true` to prevent memory leaks when sample_packing"
+                )
+                data["pad_to_sequence_len"] = True
         return data
 
     @model_validator(mode="before")