2.12.0: PydanticSerializationError when using serialize_as_any #12348
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1 of 2 issues completed
Description
Initial Checks
- I confirm that I'm using Pydantic V2
Description
Hello,
We are hitting a serialization error on Pydantic 2.12 on our RootModel implementation. Here's a snippet of the traceback:
File "/home/carl/git_projects/anta/anta/catalog.py", line 263, in to_json
return self.model_dump_json(serialize_as_any=True, exclude_unset=True, indent=2)
~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/carl/git_projects/.dev/lib/python3.13/site-packages/pydantic/main.py", line 528, in model_dump_json
return self.__pydantic_serializer__.to_json(
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
self,
^^^^^
...<13 lines>...
serialize_as_any=serialize_as_any,
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
).decode()
^
pydantic_core._pydantic_core.PydanticSerializationError: Error serializing to JSON: PydanticSerializationError: Unable to serialize unknown type: <class 'module'>
Serialization works fine on Pydantic 2.11.10.
Example Code
from types import ModuleType
from pydantic import BaseModel
class Model(BaseModel, arbitrary_types_allowed=True):
m: ModuleType
import os
m = Model(m=os)
m.model_dump_json(serialize_as_any=True)
#> pydantic_core._pydantic_core.PydanticSerializationError: Unable to serialize unknown type: <class 'module'>Python, Pydantic & OS Version
(.dev) ~/git_projects/stuff/avd (main ✗) python -c "import pydantic.version; print(pydantic.version.version_info())"
pydantic version: 2.12.0
pydantic-core version: 2.41.1
pydantic-core build: profile=release pgo=false
python version: 3.13.3 (main, Apr 9 2025, 04:03:52) [Clang 20.1.0 ]
platform: Linux-6.6.87.2-microsoft-standard-WSL2-x86_64-with-glibc2.36
related packages: pydantic-extra-types-2.10.5 pydantic-settings-2.11.0 typing_extensions-4.15.0 mypy-1.18.2
commit: unknown