[Python] How can I define a protocol for a class that contains a protocol field and use a...

I want to do this:

import typing
import dataclasses

class ConfigProtocol(typing.Protocol):
a: str

@dataclasses.dataclass
class Config:
a: str

class HasConfigProtocol(typing.Protocol):
config: ConfigProtocol


@dataclasses.dataclass
class HasConfig:
config: Config

def accepts_hasconfig(h: HasConfigProtocol):
pass

accepts_hasconfig(HasConfig(config=Config(a="")))


But in pylance it reports:

Argument of type "Position" cannot be assigned to parameter "template_position" of type "PositionProtocol" in function "__init__"
"Position" is incompatible with protocol "PositionProtocol"
"config" is invariant because it is mutable
"config" is an incompatible type
"Configuration" is incompatible with protocol "ConfigurationProtocol"


To get this to work do I need to freeze my dataclasses and provide read only access in my protocols like so?

class ConfigProtocol(typing.Protocol):
@property
def a(self) -> str:
...

@dataclasses.dataclass(frozen=True)
class Config:
a: str

class HasConfigProtocol(typing.Protocol):
@property
def config(self) -> ConfigProtocol:
...


@dataclasses.dataclass(frozen=True)
class HasConfig:
config: Config

def accepts_hasconfig(h: HasConfigProtocol):
pass

accepts_hasconfig(HasConfig(config=Config(a="")))


Long term this is the code in one module, module_a which is stand alone. There is another module_b which also exists, has similar code and is stand alone. I want to use instances of HasConfig from module_a in module_b. Because the modules do not know about eachother, I am including the same protocol definition in each of them.

To reuse protocols across modules and have instances work for both of them, the protocol definitions must be the same, and the Protocol definitions only must use @property definitions.

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