consider alias in form

fastapi/_compat.py

@@ -262,7 +262,7 @@ if PYDANTIC_V2:
     def create_body_model(
         *, fields: Sequence[ModelField], model_name: str
     ) -> Type[BaseModel]:
-        field_params = {f.field_info.alias: (f.field_info.annotation, f.field_info) for f in fields}
+        field_params = {f"{f.field_info.alias}": (f.field_info.annotation, f.field_info) for f in fields}
         BodyModel: Type[BaseModel] = create_model(model_name, **field_params)  # type: ignore[call-overload]
         return BodyModel
 

tests/test_alias_in_form.py

@@ -1,5 +1,3 @@
-from typing import Annotated
-
 from fastapi import FastAPI, Form
 from starlette.testclient import TestClient
 
@@ -7,11 +5,11 @@ from starlette.testclient import TestClient
 app:FastAPI = FastAPI()
 
 @app.post("/testing_alias")
-async def check_alias(id_test: Annotated[int, Form(alias="otherId")]):
+async def check_alias(id_test: int = Form(alias="otherId")):
     return {"other_id":id_test}
 
 @app.patch("/testing")
-async def check_without_alias(id_test:Annotated[int, Form()]):
+async def check_without_alias(id_test:int = Form()):
     return {"id_test":id_test}