fix: prevent serialization from emitting pydantic serializer warnings (#95)

Author: AbhiPrasad

py/src/braintrust/bt_json.py

@@ -1,6 +1,7 @@
 import dataclasses
 import json
 import math
+import warnings
 from typing import Any, Callable, Mapping, NamedTuple, cast, overload
 
 
@@ -53,8 +54,13 @@ def _to_bt_safe(v: Any) -> Any:
             pass
 
     # Attempt to dump a Pydantic v2 `BaseModel`.
+    # Suppress Pydantic serializer warnings that arise from generic/discriminated-union
+    # models (e.g. OpenAI's ParsedResponse[T]).  See
+    # https://github.com/braintrustdata/braintrust-sdk-python/issues/60
     try:
-        return cast(Any, v).model_dump(exclude_none=True)
+        with warnings.catch_warnings():
+            warnings.filterwarnings("ignore", message="Pydantic serializer warnings", category=UserWarning)
+            return cast(Any, v).model_dump(exclude_none=True)
     except (AttributeError, TypeError):
         pass
 

py/src/braintrust/oai.py

@@ -2,6 +2,7 @@
 import base64
 import re
 import time
+import warnings
 from collections.abc import Callable
 from typing import Any
 
@@ -1023,9 +1024,14 @@ def _try_to_dict(obj: Any) -> dict[str, Any]:
     if isinstance(obj, dict):
         return obj
     # convert a pydantic object to a dict
+    # Suppress Pydantic serializer warnings from generic/discriminated-union models
+    # (e.g. OpenAI's ParsedResponse[T]).  See
+    # https://github.com/braintrustdata/braintrust-sdk-python/issues/60
     if hasattr(obj, "model_dump") and callable(obj.model_dump):
         try:
-            return obj.model_dump()
+            with warnings.catch_warnings():
+                warnings.filterwarnings("ignore", message="Pydantic serializer warnings", category=UserWarning)
+                return obj.model_dump()
         except Exception:
             pass
     # deprecated pydantic method, try model_dump first.

py/src/braintrust/test_bt_json.py

@@ -2,6 +2,7 @@
 # pyright: reportUnknownArgumentType=false
 # pyright: reportPrivateUsage=false
 import json
+import warnings
 from typing import Any
 from unittest import TestCase
 
@@ -282,6 +283,58 @@ def test_deep_copy_numeric_and_special_keys(self):
         self.assertTrue("(1, 2)" in result or "1, 2" in result)
         self.assertIn("None", result)
 
+    def test_model_dump_no_pydantic_serializer_warnings(self):
+        """Test that model_dump() calls in _to_bt_safe don't emit Pydantic serializer warnings.
+
+        Regression test for https://github.com/braintrustdata/braintrust-sdk-python/issues/60
+        OpenAI's parsed response models (e.g. ParsedResponse[T]) emit
+        PydanticSerializationUnexpectedValue warnings from model_dump().
+        Braintrust should suppress these warnings during serialization.
+        """
+        try:
+            from pydantic import BaseModel
+        except ImportError:
+            self.skipTest("Pydantic not available")
+
+        class WarningModel(BaseModel):
+            """A model whose model_dump() emits a UserWarning, simulating OpenAI parsed responses."""
+
+            name: str
+
+            def model_dump(self, **kwargs):
+                warnings.warn(
+                    "Pydantic serializer warnings:\n  PydanticSerializationUnexpectedValue: Expected `none`",
+                    UserWarning,
+                    stacklevel=2,
+                )
+                return {"name": self.name}
+
+        obj = WarningModel(name="test")
+
+        # _to_bt_safe (via bt_safe_deep_copy) should NOT propagate the warning
+        with warnings.catch_warnings(record=True) as caught:
+            warnings.simplefilter("always")
+            result = bt_safe_deep_copy({"response": obj})
+            pydantic_warnings = [w for w in caught if "Pydantic serializer warnings" in str(w.message)]
+            assert len(pydantic_warnings) == 0, (
+                f"Expected no Pydantic serializer warnings, but got {len(pydantic_warnings)}: "
+                f"{[str(w.message) for w in pydantic_warnings]}"
+            )
+
+        assert result["response"]["name"] == "test"
+
+        # bt_dumps should also NOT propagate the warning
+        with warnings.catch_warnings(record=True) as caught:
+            warnings.simplefilter("always")
+            json_str = bt_dumps(obj)
+            pydantic_warnings = [w for w in caught if "Pydantic serializer warnings" in str(w.message)]
+            assert len(pydantic_warnings) == 0, (
+                f"Expected no Pydantic serializer warnings, but got {len(pydantic_warnings)}: "
+                f"{[str(w.message) for w in pydantic_warnings]}"
+            )
+
+        assert "test" in json_str
+
 
 @pytest.mark.vcr
 def test_to_bt_safe_special_objects():