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Combining Pydantic and semver
=============================
According to its homepage, `Pydantic <https://pydantic-docs.helpmanual.io>`_
"enforces type hints at runtime, and provides user friendly errors when data
is invalid."
To work with Pydantic>2.0, use the following steps:
1. Derive a new class from :class:`~semver.version.Version`
first and add the magic methods :py:meth:`__get_pydantic_core_schema__`
and :py:meth:`__get_pydantic_json_schema__` like this:
.. code-block:: python
from typing import Annotated, Any, Callable
from pydantic import GetJsonSchemaHandler
from pydantic_core import core_schema
from pydantic.json_schema import JsonSchemaValue
from semver import Version
class _VersionPydanticAnnotation:
@classmethod
def __get_pydantic_core_schema__(
cls,
_source_type: Any,
_handler: Callable[[Any], core_schema.CoreSchema],
) -> core_schema.CoreSchema:
def validate_from_str(value: str) -> Version:
return Version.parse(value)
from_str_schema = core_schema.chain_schema(
[
core_schema.str_schema(),
core_schema.no_info_plain_validator_function(validate_from_str),
]
)
return core_schema.json_or_python_schema(
json_schema=from_str_schema,
python_schema=core_schema.union_schema(
[
core_schema.is_instance_schema(Version),
from_str_schema,
]
),
serialization = core_schema.to_string_ser_schema(),
)
@classmethod
def __get_pydantic_json_schema__(
cls, _core_schema: core_schema.CoreSchema, handler: GetJsonSchemaHandler
) -> JsonSchemaValue:
return handler(core_schema.str_schema())
ManifestVersion = Annotated[Version, _VersionPydanticAnnotation]
2. Create a new model (in this example :class:`MyModel`) and derive
it from :py:class:`pydantic:pydantic.BaseModel`:
.. code-block:: python
import pydantic
class MyModel(pydantic.BaseModel):
version: _VersionPydanticAnnotation
3. Use your model like this:
.. code-block:: python
model = MyModel.parse_obj({"version": "1.2.3"})
The attribute :py:attr:`model.version` will be an instance of
:class:`~semver.version.Version`.
If the version is invalid, the construction will raise a
:py:class:`pydantic:pydantic_core.ValidationError`.
|
