Cyclic dependency when finding subclasses across modules

[kdkavanagh]

Say I have a base class in one file, and a specialization in another

# base.py
@dataclass
class MyBase():
      class Config(BaseConfig):
        discriminator = Discriminator(
            field="config_type",
            include_subtypes=True,
        )

# sub.py
@dataclass
class SubType(MyBase):
  config_type = "SubType"

In order for mashumaro to discover that SubType is a possible subclass to deserialize to, it must have first imported sub.py. But of course sub.py depends on base.py to pick up the base class definition. This creates a cyclic dependency which I've only been able to solve thusfar by first explicitly importing MyBase and SubType in the __init__.py before doing anything with mashumaro (w/ lazy_compilation) set to true.

A more ergonomic solution would be to define a function (subclass of Discriminator, maybe?) where I can explicitly enumerate all possible subtypes I want to support:

# base.py
@dataclass
class MyBase():
      class Config(BaseConfig):
        discriminator = Discriminator(
            field="config_type",
            include_subtypes=True,
        )
        def get_subtypes() -> Iterable[type]:
           from sub import SubType
           yield SubType

It might be tempting to just include a subtype_list: list[type] attr on Discriminator, but I dont think that'd solve the cyclic import challenge unless used with field(default_factory: get_subtypes), so really would just be an indirection