mistral, openai: support custom tokenizers in chat models (langchain-…

…ai#20901)

libs/partners/mistralai/tests/unit_tests/test_chat_models.py

@@ -1,7 +1,7 @@
 """Test MistralAI Chat API wrapper."""
 
 import os
-from typing import Any, AsyncGenerator, Dict, Generator, cast
+from typing import Any, AsyncGenerator, Dict, Generator, List, cast
 from unittest.mock import patch
 
 import pytest
@@ -190,3 +190,11 @@ def test__convert_dict_to_message_tool_call() -> None:
     )
     assert result == expected_output
     assert _convert_message_to_mistral_chat_message(expected_output) == message
+
+
+def test_custom_token_counting() -> None:
+    def token_encoder(text: str) -> List[int]:
+        return [1, 2, 3]
+
+    llm = ChatMistralAI(custom_get_token_ids=token_encoder)
+    assert llm.get_token_ids("foo") == [1, 2, 3]

libs/partners/openai/langchain_openai/chat_models/base.py

@@ -703,6 +703,8 @@ def _get_encoding_model(self) -> Tuple[str, tiktoken.Encoding]:
 
     def get_token_ids(self, text: str) -> List[int]:
         """Get the tokens present in the text with tiktoken package."""
+        if self.custom_get_token_ids is not None:
+            return self.custom_get_token_ids(text)
         # tiktoken NOT supported for Python 3.7 or below
         if sys.version_info[1] <= 7:
             return super().get_token_ids(text)

libs/partners/openai/tests/unit_tests/chat_models/test_base.py

@@ -1,7 +1,7 @@
 """Test OpenAI Chat API wrapper."""
 
 import json
-from typing import Any
+from typing import Any, List
 from unittest.mock import AsyncMock, MagicMock, patch
 
 import pytest
@@ -279,3 +279,11 @@ def test_openai_invoke_name(mock_completion: dict) -> None:
         # check return type has name
         assert res.content == "Bar Baz"
         assert res.name == "Erick"
+
+
+def test_custom_token_counting() -> None:
+    def token_encoder(text: str) -> List[int]:
+        return [1, 2, 3]
+
+    llm = ChatOpenAI(custom_get_token_ids=token_encoder)
+    assert llm.get_token_ids("foo") == [1, 2, 3]