Support django model type annotations

[rchoquet]

Hey 👋

First, thanks a lot for this lib! It really helped us deliver better quality software.

We are developing a (close to) fully typed application using Django. In lots of models we explicitly specify the type of the fields when the basic type is not precise enough, for example:

TaskStatus = Literal["todo", "done"]
class TaskConfiguration(TypedDict):
  foo: int
  bar: str

class Task(models.Model):
  status: TaskStatus = models.CharField()
  configuration: TaskConfiguration = models.JSONField()

The issue arises when we define the associated Pydantic models, we have to redefine the types for those fields:

class TaskSchema(ModelSchema):
  status: TaskStatus
  configuration: TaskConfiguration

  class Meta:
      model = Task
      fields = "__all__"

This PR makes ModelSchema aware of the type annotations and allow the previous schema to be defined as

class TaskSchema(ModelSchema):
  class Meta:
      model = Task
      fields = "__all__"

... so we are not repeating the type and avoid runtime errors when there is a Django model/Pydantic model mismatch.

This is a draft that would require more work/testing, let me know if you think this is an idea worth pursuing.

Cheers!

[vitalik]

Hi @rchoquet

Looks good

• Could you also add some docs / examples-to-documentation
• and to support python3.8/3.7 I think you need to import Literal from typing_extensions

[rchoquet]

@vitalik I added a cast to list here to fix this bug:
If optional_fields was equal to __all__, optional_fields = [f.name for f in model_fields_list] a few lines below was exhausting the model_fields_list iterator, and made for fld in model_fields_list iterate over an empty list, producing an empty Pydantic model.

[rchoquet]

I'll add the doc+examples asap

[rchoquet]

@vitalik should be good now.

[vitalik]

Hi @rchoquet looks good

could you also add docs example with JsonField - as this is actually a pretty often question

[msopacua]

Question: is this common to type your fields instead of using django-stubs?
Also, if you support this, are you going to support stubs in general?

[rchoquet]

Question: is this common to type your fields instead of using django-stubs?

I don't know, but I think you have to if you want more than the primitive types (ex: enums of string Literal, json field, ...)

Also, if you support this, are you going to support stubs in general?

What do you mean by that?

@vitalik sorry for the delay, I'll do the doc change today.

[vitalik]

Question: is this common to type your fields instead of using django-stubs?
Also, if you support this, are you going to support stubs in general?

not this has nothing to do with stubs - this let's you overrule default typing annotation when schema is automatically crated from model

[rchoquet]

@vitalik done

[rchoquet]

Hey @vitalik

Anything left to do on my side to get this merged?

[rchoquet]

Ping @vitalik