Chat template: update for processor (#35953)

* update

* we need batched nested input to always process correctly

* update a bit

* fix copies

tests/models/mllama/test_processor_mllama.py

@@ -13,6 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import json
 import shutil
 import tempfile
 import unittest
@@ -52,6 +53,20 @@ class MllamaProcessorTest(ProcessorTesterMixin, unittest.TestCase):
     def tearDown(self):
         shutil.rmtree(self.tmpdirname)
 
+    def prepare_processor_dict(self):
+        return {"chat_template": "{% for message in messages %}{% if loop.index0 == 0 %}{{ bos_token }}{% endif %}{{ '<|start_header_id|>' + message['role'] + '<|end_header_id|>\n\n' }}{% if message['content'] is string %}{{ message['content'] }}{% else %}{% for content in message['content'] %}{% if content['type'] == 'image' %}{{ '<|image|>' }}{% elif content['type'] == 'text' %}{{ content['text'] }}{% endif %}{% endfor %}{% endif %}{{ '<|eot_id|>' }}{% endfor %}{% if add_generation_prompt %}{{ '<|start_header_id|>assistant<|end_header_id|>\n\n' }}{% endif %}"}  # fmt: skip
+
+    def test_chat_template_is_saved(self):
+        processor_loaded = self.processor_class.from_pretrained(self.tmpdirname)
+        processor_dict_loaded = json.loads(processor_loaded.to_json_string())
+        # chat templates aren't serialized to json in processors
+        self.assertFalse("chat_template" in processor_dict_loaded.keys())
+
+        # they have to be saved as separate file and loaded back from that file
+        # so we check if the same template is loaded
+        processor_dict = self.prepare_processor_dict()
+        self.assertTrue(processor_loaded.chat_template == processor_dict.get("chat_template", None))
+
     def test_apply_chat_template(self):
         # Message contains content which a mix of lists with images and image urls and string
         messages = [