upgrade is_record_type to use TypeGuard

[DXsmiley]

Would it be possible to utilise TypeGuard on this function in order to leverage the return value at the callsite for static type checking?

atproto/atproto/xrpc_client/models/utils.py

Line 202 in d5e2293

def is_record_type(model: ModelBase, expected_type: t.Union[str, types.ModuleType]) -> bool:

I'd do it myself but I don't feel I understand enough about the details of the library at this point to get it right

[MarshalX]

sorry for the long response. I'll take a look after releasing #127

mypy is not fully integrated into atproto sdk :( but i have a plan for it

https://github.com/MarshalX/atproto/blob/main/pyproject.toml#L78-L80

[DXsmiley]

Making a note so nobody else falls over the same problem, hopefully:

I spent a while banging my head against the wall on this one only to find that there was a bug in pyright which only recently got fixed.

Specifically:

Bug Fix: Fixed several issues with logic that performs protocol matching against a module, including a false positive error when matching against a generic protocol.

Here's my current (incomplete) approach, if anyone's interested:

from typing import TypeVar, Protocol, Any, Type
from typing_extensions import TypeGuard
from atproto.xrpc_client.models.base import ModelBase
from atproto.xrpc_client.models.utils import is_record_type as original_is_record_type
from atproto.xrpc_client import models

T = TypeVar('T', bound=ModelBase)

class HasAMainModel(Protocol[T]):
    Main: Type[T]

def is_record_type(record: Any, model: HasAMainModel[T]) -> TypeGuard[T]:
    return original_is_record_type(record, model)  # type: ignore

def test(x: Any):
    if is_record_type(x, models.AppBskyEmbedImages):
        reveal_type(x) # correctly identified as atproto.xrpc_client.models.app.bsky.embed.images.Main

Also need to consider that this actually isn't quite the same as an is_instance check so we should be careful not to assert too much about the type via the TypeGuard.