Generate: GenerationConfig can overwrite attributes at from_pretrained time (#24238)

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

tests/generation/test_configuration_utils.py

@@ -93,6 +93,31 @@ class GenerationConfigTest(unittest.TestCase):
         generation_config = GenerationConfig.from_model_config(new_config)
         assert not hasattr(generation_config, "foo")  # no new kwargs should be initialized if from config
 
+    def test_kwarg_init(self):
+        """Tests that we can overwrite attributes at `from_pretrained` time."""
+        default_config = GenerationConfig()
+        self.assertEqual(default_config.temperature, 1.0)
+        self.assertEqual(default_config.do_sample, False)
+        self.assertEqual(default_config.num_beams, 1)
+
+        config = GenerationConfig(
+            do_sample=True,
+            temperature=0.7,
+            length_penalty=1.0,
+            bad_words_ids=[[1, 2, 3], [4, 5]],
+        )
+        self.assertEqual(config.temperature, 0.7)
+        self.assertEqual(config.do_sample, True)
+        self.assertEqual(config.num_beams, 1)
+
+        with tempfile.TemporaryDirectory() as tmp_dir:
+            config.save_pretrained(tmp_dir)
+            loaded_config = GenerationConfig.from_pretrained(tmp_dir, temperature=1.0)
+
+        self.assertEqual(loaded_config.temperature, 1.0)
+        self.assertEqual(loaded_config.do_sample, True)
+        self.assertEqual(loaded_config.num_beams, 1)  # default value
+
 
 @is_staging_test
 class ConfigPushToHubTester(unittest.TestCase):