Generate: ignore warning when `generation_config.max_length` is set to `None` (#26147)

src/transformers/generation/flax_utils.py

@@ -389,7 +389,7 @@ class FlaxGenerationMixin:
                 UserWarning,
             )
         elif generation_config.max_new_tokens is not None:
-            if not has_default_max_length:
+            if not has_default_max_length and generation_config.max_length is not None:
                 logger.warning(
                     f"Both `max_new_tokens` (={generation_config.max_new_tokens}) and `max_length`(="
                     f"{generation_config.max_length}) seem to have been set. `max_new_tokens` will take precedence. "

src/transformers/generation/tf_utils.py

@@ -841,7 +841,7 @@ class TFGenerationMixin:
                 UserWarning,
             )
         elif generation_config.max_new_tokens is not None:
-            if not has_default_max_length:
+            if not has_default_max_length and generation_config.max_length is not None:
                 logger.warning(
                     f"Both `max_new_tokens` (={generation_config.max_new_tokens}) and `max_length`(="
                     f"{generation_config.max_length}) seem to have been set. `max_new_tokens` will take precedence. "

src/transformers/generation/utils.py

@@ -1517,7 +1517,7 @@ class GenerationMixin:
         input_ids_length = input_ids.shape[-1]
         has_default_max_length = kwargs.get("max_length") is None and generation_config.max_length is not None
         if generation_config.max_new_tokens is not None:
-            if not has_default_max_length:
+            if not has_default_max_length and generation_config.max_length is not None:
                 logger.warning(
                     f"Both `max_new_tokens` (={generation_config.max_new_tokens}) and `max_length`(="
                     f"{generation_config.max_length}) seem to have been set. `max_new_tokens` will take precedence. "