Generate: save generation config with the models' .save_pretrained() (#21264)

tests/test_modeling_common.py

@@ -63,6 +63,8 @@ from transformers.testing_utils import (
     torch_device,
 )
 from transformers.utils import (
+    CONFIG_NAME,
+    GENERATION_CONFIG_NAME,
     SAFE_WEIGHTS_INDEX_NAME,
     SAFE_WEIGHTS_NAME,
     WEIGHTS_INDEX_NAME,
@@ -275,6 +277,13 @@ class ModelTesterMixin:
 
             with tempfile.TemporaryDirectory() as tmpdirname:
                 model.save_pretrained(tmpdirname)
+
+                # the config file (and the generation config file, if it can generate) should be saved
+                self.assertTrue(os.path.exists(os.path.join(tmpdirname, CONFIG_NAME)))
+                self.assertEqual(
+                    model.can_generate(), os.path.exists(os.path.join(tmpdirname, GENERATION_CONFIG_NAME))
+                )
+
                 model = model_class.from_pretrained(tmpdirname)
                 model.to(torch_device)
                 with torch.no_grad():