Support type hints in model fields

Being aware that you don’t like type hints (#1298), I’ll be bold and ask if you would allow users to annotate their models with type hints?

Problem:

class User(peewee.Model):
    name = CharField()


u = User()
u.name = 'Joe'  # mypy will nag because inferred type is 'CharField'

Cannot:

class User(peewee.Model):
    name = CharField()  # type: str


u = User()
u.name = 'Joe'  # sure works now but
User.select().where(User.name.id == 1)  # violation as User.name is marked as 'str'

Would it be possible to have separate fields for class and instance:

class User(peewee.Model):

    name_c = CharField(instance_field='name')
    name = None  # type: str - simply a placeholder for mypy type
    name: str  # in py3.6+


u = User()
u.name = 'Joe'  # would now have 'str' type
User.select().where(User.name_c.id == 1)  # would have 'CharField' type

The idea being that instance would override the name field with getter/setter (declared as instance_field).

Yeah it is hackish, but it would be better than having to # type: <override> everywhere.

I believe this couldn’t go to typeshed stubs anyway due to being context-specific.

[coleifer]

I think type hints are misguided and unpythonic, and it’s my stance that they will never be supported by peewee. Python is a high-level dynamic language, peewee plays to these strengths. You couldn’t implement peewee in go, it’d look completely different.

I enjoy statically typed languages. When I want static typing I use c or go. When I want dynamic or metaprogramming I use python.

These are my opinions and I understand that others have their own views. My goals for peewee are to make it composable and consistent, and I feel I can do that best by using python’s dynamism.

[ce603]

I would also like to request this, because it helps with code completion.

For example, consider the code:

my_user = User.select().first()

This returns a <Model: User>, but it would be great if it type hinted to a User object, because on the next line of code, I would get a list of functions available to user (for example, if the User class had a function user_function(), I would see user_function() in the list of suggestions in the code completion hints. I know that I can specify this using # type: User, but I’d prefer it be automatic.

Also, is it possible to specify a return collection type? For example, in SQLAlchemy, I can do something like

orders = relationship("Order", back_populates="user", collection_class=Orders)  # type: Orders

and the orders will be returned as an Orders object, which is a custom class object that inherits from InstrumentedList. This allows me to add special functions, such as .most_recent(), .to_df(), etc…