Change Pydantic's inherited BaseModel's attribute precedence in JSON schema - json

Question

I'm using pydantic 1.6.1 and fastapi 0.61.1 with Python 3.8.3. Here's how I've tried defining the models:
class UserBase(BaseModel):
name: str
class UserCreate(UserBase):
password: str
class UserInfo(UserBase):
id: str
group: Optional[GroupInfo] = None
The issue I'm having with this setup is that the schema is built such that the name attribute is on top of the remaining attributes like so - in this case, while using UserInfo as the endpoint's response_model:
[
{
"name": "string",
"id": "string",
"group": {
"name": "string"
}
}
]
Yet I'd like to be able to set them up like this:
[
{
"id": "string",
"name": "string",
"group": {
"name": "string"
}
}
]
Is there a way I can manually set a custom order for the attributes in the JSON response's schema?

Answer 1

As I mentioned in my comment, it doesn't really matter the order of the JSON, but when it comes to schema generation, it can be helpful.
You need to decouple the id field from UserInfo model as
class UserID(BaseModel):
id: str
class UserInfo(UserBase, UserID): # `UserID` should be second
group: Optional[GroupInfo] = None
This will generate the following JSON schema,
{
"id": "string",
"name": "string",
"group": {
"name": "string"
}
}
Bit more ugly solution (IMO)
patch the .__fields__ as
class UserBase(BaseModel):
name: str
class UserCreate(UserBase):
password: str
class UserInfo(UserBase):
id: str
group: Optional[GroupInfo] = None
fields = UserInfo.__fields__.copy()
UserInfo.__fields__ = {"id": fields.pop("id"), **fields}