🐛 Fix support for tagged union with discriminator inside of `Annotated` with `Body()` (#14512)

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Sebastián Ramírez 2025-12-12 06:31:21 -08:00 committed by GitHub
parent 1fcec88ad2
commit c0556ac3a5
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2 changed files with 255 additions and 4 deletions

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@ -18,7 +18,7 @@ from typing import (
from fastapi._compat import may_v1, shared
from fastapi.openapi.constants import REF_TEMPLATE
from fastapi.types import IncEx, ModelNameMap, UnionType
from pydantic import BaseModel, ConfigDict, TypeAdapter, create_model
from pydantic import BaseModel, ConfigDict, Field, TypeAdapter, create_model
from pydantic import PydanticSchemaGenerationError as PydanticSchemaGenerationError
from pydantic import PydanticUndefinedAnnotation as PydanticUndefinedAnnotation
from pydantic import ValidationError as ValidationError
@ -50,6 +50,45 @@ UndefinedType = PydanticUndefinedType
evaluate_forwardref = eval_type_lenient
Validator = Any
# TODO: remove when dropping support for Pydantic < v2.12.3
_Attrs = {
"default": ...,
"default_factory": None,
"alias": None,
"alias_priority": None,
"validation_alias": None,
"serialization_alias": None,
"title": None,
"field_title_generator": None,
"description": None,
"examples": None,
"exclude": None,
"exclude_if": None,
"discriminator": None,
"deprecated": None,
"json_schema_extra": None,
"frozen": None,
"validate_default": None,
"repr": True,
"init": None,
"init_var": None,
"kw_only": None,
}
# TODO: remove when dropping support for Pydantic < v2.12.3
def asdict(field_info: FieldInfo) -> Dict[str, Any]:
attributes = {}
for attr in _Attrs:
value = getattr(field_info, attr, Undefined)
if value is not Undefined:
attributes[attr] = value
return {
"annotation": field_info.annotation,
"metadata": field_info.metadata,
"attributes": attributes,
}
class BaseConfig:
pass
@ -95,10 +134,15 @@ class ModelField:
warnings.simplefilter(
"ignore", category=UnsupportedFieldAttributeWarning
)
# TODO: remove after dropping support for Python 3.8 and
# setting the min Pydantic to v2.12.3 that adds asdict()
field_dict = asdict(self.field_info)
annotated_args = (
self.field_info.annotation,
*self.field_info.metadata,
self.field_info,
field_dict["annotation"],
*field_dict["metadata"],
# this FieldInfo needs to be created again so that it doesn't include
# the old field info metadata and only the rest of the attributes
Field(**field_dict["attributes"]),
)
self._type_adapter: TypeAdapter[Any] = TypeAdapter(
Annotated[annotated_args],

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@ -0,0 +1,207 @@
# Ref: https://github.com/fastapi/fastapi/discussions/14495
from typing import Union
import pytest
from fastapi import FastAPI
from fastapi.testclient import TestClient
from inline_snapshot import snapshot
from pydantic import BaseModel
from typing_extensions import Annotated
from .utils import needs_pydanticv2
@pytest.fixture(name="client")
def client_fixture() -> TestClient:
from fastapi import Body
from pydantic import Discriminator, Tag
class Cat(BaseModel):
pet_type: str = "cat"
meows: int
class Dog(BaseModel):
pet_type: str = "dog"
barks: float
def get_pet_type(v):
assert isinstance(v, dict)
return v.get("pet_type", "")
Pet = Annotated[
Union[Annotated[Cat, Tag("cat")], Annotated[Dog, Tag("dog")]],
Discriminator(get_pet_type),
]
app = FastAPI()
@app.post("/pet/assignment")
async def create_pet_assignment(pet: Pet = Body()):
return pet
@app.post("/pet/annotated")
async def create_pet_annotated(pet: Annotated[Pet, Body()]):
return pet
client = TestClient(app)
return client
@needs_pydanticv2
def test_union_body_discriminator_assignment(client: TestClient) -> None:
response = client.post("/pet/assignment", json={"pet_type": "cat", "meows": 5})
assert response.status_code == 200, response.text
assert response.json() == {"pet_type": "cat", "meows": 5}
@needs_pydanticv2
def test_union_body_discriminator_annotated(client: TestClient) -> None:
response = client.post("/pet/annotated", json={"pet_type": "dog", "barks": 3.5})
assert response.status_code == 200, response.text
assert response.json() == {"pet_type": "dog", "barks": 3.5}
@needs_pydanticv2
def test_openapi_schema(client: TestClient) -> None:
response = client.get("/openapi.json")
assert response.status_code == 200, response.text
assert response.json() == snapshot(
{
"openapi": "3.1.0",
"info": {"title": "FastAPI", "version": "0.1.0"},
"paths": {
"/pet/assignment": {
"post": {
"summary": "Create Pet Assignment",
"operationId": "create_pet_assignment_pet_assignment_post",
"requestBody": {
"content": {
"application/json": {
"schema": {
"anyOf": [
{"$ref": "#/components/schemas/Cat"},
{"$ref": "#/components/schemas/Dog"},
],
"title": "Pet",
}
}
},
"required": True,
},
"responses": {
"200": {
"description": "Successful Response",
"content": {"application/json": {"schema": {}}},
},
"422": {
"description": "Validation Error",
"content": {
"application/json": {
"schema": {
"$ref": "#/components/schemas/HTTPValidationError"
}
}
},
},
},
}
},
"/pet/annotated": {
"post": {
"summary": "Create Pet Annotated",
"operationId": "create_pet_annotated_pet_annotated_post",
"requestBody": {
"content": {
"application/json": {
"schema": {
"oneOf": [
{"$ref": "#/components/schemas/Cat"},
{"$ref": "#/components/schemas/Dog"},
],
"title": "Pet",
}
}
},
"required": True,
},
"responses": {
"200": {
"description": "Successful Response",
"content": {"application/json": {"schema": {}}},
},
"422": {
"description": "Validation Error",
"content": {
"application/json": {
"schema": {
"$ref": "#/components/schemas/HTTPValidationError"
}
}
},
},
},
}
},
},
"components": {
"schemas": {
"Cat": {
"properties": {
"pet_type": {
"type": "string",
"title": "Pet Type",
"default": "cat",
},
"meows": {"type": "integer", "title": "Meows"},
},
"type": "object",
"required": ["meows"],
"title": "Cat",
},
"Dog": {
"properties": {
"pet_type": {
"type": "string",
"title": "Pet Type",
"default": "dog",
},
"barks": {"type": "number", "title": "Barks"},
},
"type": "object",
"required": ["barks"],
"title": "Dog",
},
"HTTPValidationError": {
"properties": {
"detail": {
"items": {
"$ref": "#/components/schemas/ValidationError"
},
"type": "array",
"title": "Detail",
}
},
"type": "object",
"title": "HTTPValidationError",
},
"ValidationError": {
"properties": {
"loc": {
"items": {
"anyOf": [{"type": "string"}, {"type": "integer"}]
},
"type": "array",
"title": "Location",
},
"msg": {"type": "string", "title": "Message"},
"type": {"type": "string", "title": "Error Type"},
},
"type": "object",
"required": ["loc", "msg", "type"],
"title": "ValidationError",
},
}
},
}
)