[IDEA] Alternate model syntax

In trying to solve the DB → python type mapping, and the advent of typing, a possible solution is to define types that then get evaluated into both Python and DB types:

This also raises the question of a cleaner (more modern) model definition, by defining the type:

Since py3.6 we have the typed variables:

class Author(Model):
    name: str[255]
    books: reverse_fk[Book]

class Book(Model):
    title: str[255]
    author: Author
    published: datetime
    logo: bytes = None
    pages: int
    extra: JSONField = {}
    price: Decimal[18,5]
    created_at: datetime[auto_now_add]

Which is already standard in Py3.7 @dataclass

We could extend type definitions so we can build model definitions off of types. e.g. str[100] = 'some default' → CharField(max_length=100, default='some default') The syntax is not comprehensive, but we could probably use type declarations for a large portion of use cases.

This would require Py3.6+ to function, so dropping Py3.5 & PyPy.

[grigi]

Yes, all valid points. This is feeling more like something that we may not want to do as is in my proposal.

Technically the problem is as follows: Lets say I define a class Stuff withval=IntField() It appears that for Stuff val is Intfield and a class variable. But due to the metaclass rewriting the class, Stuff val is int and an instance variable.

In the name of being succinct (and use metaclasses as a solution) we will end up confusing anything that tries to do Type determinism.

I added a PyLint plugin so that it can stop complaining about everything, but at that time Mypy didn’t have plugins yet.

I’d love a Mypy plugin 😁

[antonagestam]

Cool! I think mypy support really would be a great feature.

The plugins for attrs and dataclasses that are shipped with mypy are probably good places to look for inspiration, and they should probably give a somewhat good indication of the amount of work that’s required.

• dataclasses plugin: https://github.com/python/mypy/blob/00ccb783de8b43bcfcc22184da8846a927bcb9db/mypy/plugins/dataclasses.py
• attrs plugin: https://github.com/python/mypy/blob/00ccb783de8b43bcfcc22184da8846a927bcb9db/mypy/plugins/attrs.py