Is your feature request related to a problem? Please describe.
msgspec support for discriminated unions is not currently supported by datamodel-code-generator and it would be great to support discriminated unions.
Currently if generating discriminated union using the msgspec output, e.g from tests/data/jsonschema/discriminator_literals.json attempting to decode a yaml file with the generated code will result in at least two issues:
- erroneous
Optionaltype wrapping thetype_field; and - if the
Optionaltype wrapper is removed then when attempting to useResponsetype to decode an input the following error is raised:TypeError: If a type union contains multiple Struct types, all Struct types must be tagged (viatagortag_fieldkwarg) - typetyping.Annotated[typing.Union[main.Type1, main.Type2], msgspec.Meta(title='Inner')]is not supported
$ datamodel-codegen --input tests/data/jsonschema/discriminator_literals.json --input-file-type jsonschema --output tests/data/expected/main/main_jsonschema_discriminator_literals_msgspec/output.py --disable-timestamp --enable-version-header --output-model-type msgspec.Struct --target-python 3.9
$ cat <<"EOF" >> tests/data/expected/main/main_jsonschema_discriminator_literals_msgspec/output.py
if __name__ == "__main__":
import msgspec
d = """\
---
inner:
type_: a
"""
print(msgspec.yaml.decode(d, type=Response))
EOF
$ › python tests/data/expected/main/main_jsonschema_discriminator_literals_msgspec/output.py
Traceback (most recent call last):
File "tests/data/expected/main/main_jsonschema_discriminator_literals_msgspec/output.py ", line 31, in <module>
print(msgspec.yaml.decode(d, type=Response))
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "venv/lib/python3.11/site-packages/msgspec/yaml.py", line 161, in decode
return _convert(
^^^^^^^^^
TypeError: If a type union contains multiple Struct types, all Struct types must be tagged (via `tag` or `tag_field` kwarg) - type `typing.Annotated[typing.Union[__main__.Type1, __main__.Type2], msgspec.Meta(title='Inner')]` is not supportedoutput.py with Optional type wrapper removed.
# generated by datamodel-codegen:
# filename: discriminator_literals.json
# version: 0.0.0
from __future__ import annotations
from typing import Annotated, Literal, Union
from msgspec import Meta, Struct, field
class Type1(Struct):
type_: Annotated[Literal['a'], Meta(title='Type ')] = 'a'
class Type2(Struct):
type_: Annotated[Literal['b'], Meta(title='Type ')] = 'b'
class Response(Struct):
inner: Annotated[Union[Type1, Type2], Meta(title='Inner')]
if __name__ == "__main__":
import msgspec
d = """\
---
inner:
type_: a
"""
print(msgspec.yaml.decode(d, type=Response))Describe the solution you'd like
To be able to define a discriminated union in jsonschema and generate the correct python/msgspec output. Preferably in the using the ClassVar format suggested by: jcrist/msgspec#338 (comment)
Additional context
Added example output test to: aaa3f7a unsure how to go about adding support for discriminators to the msgspec output.
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