fix rag retriever save pretrained (#7399)

src/transformers/retrieval_rag.py

@@ -312,8 +312,8 @@ class RagRetriever:
     def save_pretrained(self, save_directory):
         self.config.save_pretrained(save_directory)
         rag_tokenizer = RagTokenizer(
-            question_encoder_tokenizer=self.question_encoder_tokenizer,
-            generator_tokenizer=self.generator_tokenizer,
+            question_encoder=self.question_encoder_tokenizer,
+            generator=self.generator_tokenizer,
         )
         rag_tokenizer.save_pretrained(save_directory)
 

tests/test_retrieval_rag.py

@@ -168,6 +168,11 @@ class RagRetrieverTest(TestCase):
         self.assertEqual(doc_dicts[1]["id"][0], "0")  # max inner product is reached with first doc
         self.assertListEqual(doc_ids.tolist(), [[1], [0]])
 
+    def test_save_and_from_pretrained(self):
+        retriever = self.get_dummy_hf_index_retriever()
+        with tempfile.TemporaryDirectory() as tmp_dirname:
+            retriever.save_pretrained(tmp_dirname)
+
     def test_legacy_index_retriever_retrieve(self):
         n_docs = 1
         retriever = self.get_dummy_legacy_index_retriever()