Allow annotations for specifying fields instead of class attributes

[esoterra]

The new typing.NamedTuple class offers a new way to specify named tuples using colon based type labels.

I would like this syntax to be available for defining model classes so that the Dog example in the README can be written like this

class Dog(Model):
     name: fields.Str()
     hates_cats: fields.Optional(fields.Bool, default=True)

Reference:
https://docs.python.org/3/library/typing.html#typing.NamedTuple

[rossmacarthur]

Thanks for the suggestion. This looks pretty easy to implement (they simply end up in a class attribute __annotations__). I think the only question that would need to be resolved is what happens in cases where both are used.

For example:

class Dog(Model):
    name: fields.Str()
    name = fields.Int()

or

class Dog(Model):
    name: fields.Str() = 'hello'

or even just a mix

class Dog(Model):
    name: fields.Str()
    hates_cats = fields.Bool()

• If annotations are used should we ignore any further class attributes?
• Does the one override the other? I.e. if annotations and class attributes assign an identically named attribute which has priority then?
• Do we error if both are used?

[rossmacarthur]

Additionally I think it would be fine for these annotations used the same "resolving" of types and model classes into fields that are used for container fields like fields.Dict. So you would be able to do something like this

class Dog(Model):
    name: str
    hates_cats: fields.Optional(bool, default=True)

[esoterra]

Thanks, this looks like it's headed where I was hoping it would.