Jonny Saunders 1 day ago
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  1. 18
      fastapi/dependencies/utils.py
  2. 326
      tests/test_forms_defaults.py
  3. 4
      tests/test_forms_single_model.py

18
fastapi/dependencies/utils.py

@ -714,7 +714,10 @@ def _validate_value_with_model_field(
def _get_multidict_value(
field: ModelField, values: Mapping[str, Any], alias: Union[str, None] = None
field: ModelField,
values: Mapping[str, Any],
alias: Union[str, None] = None,
form_input: bool = False,
) -> Any:
alias = alias or field.alias
if is_sequence_field(field) and isinstance(values, (ImmutableMultiDict, Headers)):
@ -724,14 +727,14 @@ def _get_multidict_value(
if (
value is None
or (
isinstance(field.field_info, params.Form)
(isinstance(field.field_info, params.Form) or form_input)
and isinstance(value, str) # For type checks
and value == ""
)
or (is_sequence_field(field) and len(value) == 0)
):
if field.required:
return
if form_input or field.required:
return None
else:
return deepcopy(field.default)
return value
@ -843,11 +846,12 @@ async def _extract_form_body(
received_body: FormData,
) -> Dict[str, Any]:
values = {}
field_aliases = {field.alias for field in body_fields}
first_field = body_fields[0]
first_field_info = first_field.field_info
for field in body_fields:
value = _get_multidict_value(field, received_body)
value = _get_multidict_value(field, received_body, form_input=True)
if (
isinstance(first_field_info, params.File)
and is_bytes_field(field)
@ -875,8 +879,10 @@ async def _extract_form_body(
value = serialize_sequence_value(field=field, value=results)
if value is not None:
values[field.alias] = value
# preserve extra keys not in model body fields for validation
for key, value in received_body.items():
if key not in values:
if key not in field_aliases:
values[key] = value
return values

326
tests/test_forms_defaults.py

@ -0,0 +1,326 @@
from typing import Optional
import pytest
from fastapi import FastAPI, Form
from fastapi._compat import PYDANTIC_V2
from pydantic import BaseModel, Field
from starlette.testclient import TestClient
from typing_extensions import Annotated
from .utils import needs_pydanticv2
if PYDANTIC_V2:
from pydantic import model_validator
else:
from pydantic import root_validator
def _validate_input(value: dict) -> dict:
"""
model validators in before mode should receive values passed
to model instantiation before any further validation
"""
# we should not be double-instantiating the models
assert isinstance(value, dict)
value["init_input"] = value.copy()
# differentiate between explicit Nones and unpassed values
if "true_if_unset" not in value:
value["true_if_unset"] = True
return value
class Parent(BaseModel):
init_input: dict
# importantly, no default here
if PYDANTIC_V2:
@model_validator(mode="before")
def validate_inputs(cls, value: dict) -> dict:
return _validate_input(value)
else:
@root_validator(pre=True)
def validate_inputs(cls, value: dict) -> dict:
return _validate_input(value)
class StandardModel(Parent):
default_true: bool = True
default_false: bool = False
default_none: Optional[bool] = None
default_zero: int = 0
default_str: str = "foo"
true_if_unset: Optional[bool] = None
class FieldModel(Parent):
default_true: bool = Field(default=True)
default_false: bool = Field(default=False)
default_none: Optional[bool] = Field(default=None)
default_zero: int = Field(default=0)
default_str: str = Field(default="foo")
true_if_unset: Optional[bool] = Field(default=None)
if PYDANTIC_V2:
class AnnotatedFieldModel(Parent):
default_true: Annotated[bool, Field(default=True)]
default_false: Annotated[bool, Field(default=False)]
default_none: Annotated[Optional[bool], Field(default=None)]
default_zero: Annotated[int, Field(default=0)]
default_str: Annotated[str, Field(default="foo")]
true_if_unset: Annotated[Optional[bool], Field(default=None)]
class AnnotatedFormModel(Parent):
default_true: Annotated[bool, Form(default=True)]
default_false: Annotated[bool, Form(default=False)]
default_none: Annotated[Optional[bool], Form(default=None)]
default_zero: Annotated[int, Form(default=0)]
default_str: Annotated[str, Form(default="foo")]
true_if_unset: Annotated[Optional[bool], Form(default=None)]
class SimpleForm(BaseModel):
"""https://github.com/fastapi/fastapi/pull/13464#issuecomment-2708378172"""
foo: Annotated[str, Form(default="bar")]
alias_with: Annotated[str, Form(alias="with", default="nothing")]
class ResponseModel(BaseModel):
fields_set: list = Field(default_factory=list)
dumped_fields_no_exclude: dict = Field(default_factory=dict)
dumped_fields_exclude_default: dict = Field(default_factory=dict)
dumped_fields_exclude_unset: dict = Field(default_factory=dict)
dumped_fields_no_meta: dict = Field(default_factory=dict)
init_input: dict
@classmethod
def from_value(cls, value: Parent) -> "ResponseModel":
if PYDANTIC_V2:
return ResponseModel(
init_input=value.init_input,
fields_set=list(value.model_fields_set),
dumped_fields_no_exclude=value.model_dump(),
dumped_fields_exclude_default=value.model_dump(exclude_defaults=True),
dumped_fields_exclude_unset=value.model_dump(exclude_unset=True),
dumped_fields_no_meta=value.model_dump(
exclude={"init_input", "fields_set"}
),
)
else:
return ResponseModel(
init_input=value.init_input,
fields_set=list(value.__fields_set__),
dumped_fields_no_exclude=value.dict(),
dumped_fields_exclude_default=value.dict(exclude_defaults=True),
dumped_fields_exclude_unset=value.dict(exclude_unset=True),
dumped_fields_no_meta=value.dict(exclude={"init_input", "fields_set"}),
)
app = FastAPI()
@app.post("/form/standard")
async def form_standard(value: Annotated[StandardModel, Form()]) -> ResponseModel:
return ResponseModel.from_value(value)
@app.post("/form/field")
async def form_field(value: Annotated[FieldModel, Form()]) -> ResponseModel:
return ResponseModel.from_value(value)
if PYDANTIC_V2:
@app.post("/form/annotated-field")
async def form_annotated_field(
value: Annotated[AnnotatedFieldModel, Form()],
) -> ResponseModel:
return ResponseModel.from_value(value)
@app.post("/form/annotated-form")
async def form_annotated_form(
value: Annotated[AnnotatedFormModel, Form()],
) -> ResponseModel:
return ResponseModel.from_value(value)
@app.post("/form/inlined")
async def form_inlined(
default_true: Annotated[bool, Form()] = True,
default_false: Annotated[bool, Form()] = False,
default_none: Annotated[Optional[bool], Form()] = None,
default_zero: Annotated[int, Form()] = 0,
default_str: Annotated[str, Form()] = "foo",
true_if_unset: Annotated[Optional[bool], Form()] = None,
):
"""
Rather than using a model, inline the fields in the endpoint.
This doesn't use the `ResponseModel` pattern, since that is just to
test the instantiation behavior prior to the endpoint function.
Since we are receiving the values of the fields here (and thus,
having the defaults is correct behavior), we just return the values.
"""
if true_if_unset is None:
true_if_unset = True
return {
"default_true": default_true,
"default_false": default_false,
"default_none": default_none,
"default_zero": default_zero,
"default_str": default_str,
"true_if_unset": true_if_unset,
}
@app.post("/json/standard")
async def json_standard(value: StandardModel) -> ResponseModel:
return ResponseModel.from_value(value)
@app.post("/json/field")
async def json_field(value: FieldModel) -> ResponseModel:
return ResponseModel.from_value(value)
if PYDANTIC_V2:
@app.post("/json/annotated-field")
async def json_annotated_field(value: AnnotatedFieldModel) -> ResponseModel:
return ResponseModel.from_value(value)
@app.post("/json/annotated-form")
async def json_annotated_form(value: AnnotatedFormModel) -> ResponseModel:
return ResponseModel.from_value(value)
@app.post("/simple-form")
def form_endpoint(model: Annotated[SimpleForm, Form()]) -> dict:
"""https://github.com/fastapi/fastapi/pull/13464#issuecomment-2708378172"""
return model.model_dump()
if PYDANTIC_V2:
MODEL_TYPES = {
"standard": StandardModel,
"field": FieldModel,
"annotated-field": AnnotatedFieldModel,
"annotated-form": AnnotatedFormModel,
}
else:
MODEL_TYPES = {
"standard": StandardModel,
"field": FieldModel,
}
ENCODINGS = ("form", "json")
@pytest.fixture(scope="module")
def client() -> TestClient:
with TestClient(app) as test_client:
yield test_client
@pytest.mark.parametrize("encoding", ENCODINGS)
@pytest.mark.parametrize("model_type", MODEL_TYPES.keys())
def test_no_prefill_defaults_all_unset(encoding, model_type, client):
"""
When the model is instantiated by the server, it should not have its defaults prefilled
"""
endpoint = f"/{encoding}/{model_type}"
if encoding == "form":
res = client.post(endpoint, data={})
else:
res = client.post(endpoint, json={})
assert res.status_code == 200
response_model = ResponseModel(**res.json())
assert response_model.init_input == {}
assert len(response_model.fields_set) == 2
assert response_model.dumped_fields_no_exclude["true_if_unset"] is True
@pytest.mark.parametrize("encoding", ENCODINGS)
@pytest.mark.parametrize("model_type", MODEL_TYPES.keys())
def test_no_prefill_defaults_partially_set(encoding, model_type, client):
"""
When the model is instantiated by the server, it should not have its defaults prefilled,
and pydantic should be able to differentiate between unset and default values when some are passed
"""
endpoint = f"/{encoding}/{model_type}"
if encoding == "form":
data = {"true_if_unset": "False", "default_false": "True", "default_zero": "0"}
res = client.post(endpoint, data=data)
else:
data = {"true_if_unset": False, "default_false": True, "default_zero": 0}
res = client.post(endpoint, json=data)
if PYDANTIC_V2:
dumped_exclude_unset = MODEL_TYPES[model_type](**data).model_dump(
exclude_unset=True
)
dumped_exclude_default = MODEL_TYPES[model_type](**data).model_dump(
exclude_defaults=True
)
else:
dumped_exclude_unset = MODEL_TYPES[model_type](**data).dict(exclude_unset=True)
dumped_exclude_default = MODEL_TYPES[model_type](**data).dict(
exclude_defaults=True
)
assert res.status_code == 200
response_model = ResponseModel(**res.json())
assert response_model.init_input == data
assert len(response_model.fields_set) == 4
assert response_model.dumped_fields_exclude_unset == dumped_exclude_unset
assert response_model.dumped_fields_no_exclude["true_if_unset"] is False
assert "default_zero" not in dumped_exclude_default
assert "default_zero" not in response_model.dumped_fields_exclude_default
@needs_pydanticv2
def test_casted_empty_defaults(client: TestClient):
"""https://github.com/fastapi/fastapi/pull/13464#issuecomment-2708378172"""
form_content = {"foo": "", "with": ""}
response = client.post("/simple-form", data=form_content)
response_content = response.json()
assert response_content["foo"] == "bar" # Expected :'bar' -> Actual :''
assert response_content["alias_with"] == "nothing" # ok
@pytest.mark.parametrize("model_type", list(MODEL_TYPES.keys()) + ["inlined"])
def test_empty_string_inputs(model_type, client):
"""
Form inputs with no input are empty strings,
these should be treated as being unset.
"""
data = {
"default_true": "",
"default_false": "",
"default_none": "",
"default_str": "",
"default_zero": "",
"true_if_unset": "",
}
response = client.post(f"/form/{model_type}", data=data)
assert response.status_code == 200
if model_type != "inlined":
response_model = ResponseModel(**response.json())
assert set(response_model.fields_set) == {"true_if_unset", "init_input"}
response_data = response_model.dumped_fields_no_meta
else:
response_data = response.json()
assert response_data == {
"default_true": True,
"default_false": False,
"default_none": None,
"default_zero": 0,
"default_str": "foo",
"true_if_unset": True,
}

4
tests/test_forms_single_model.py

@ -104,13 +104,13 @@ def test_no_data():
"type": "missing",
"loc": ["body", "username"],
"msg": "Field required",
"input": {"tags": ["foo", "bar"], "with": "nothing"},
"input": {},
},
{
"type": "missing",
"loc": ["body", "lastname"],
"msg": "Field required",
"input": {"tags": ["foo", "bar"], "with": "nothing"},
"input": {},
},
]
}

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