How to make Ren'Py 8 load raw Python files from .rpa archives

load_python.py

import renpy.loader

from importlib.machinery import ModuleSpec
from types import ModuleType
from typing import Any, List, Optional, Union


class DummyLoader:

    def __init__(self) -> None:
        pass

    def create_module(self, spec: ModuleSpec) -> None:
        return None

    def exec_module(self, module: ModuleType) -> None:
        pass


class PythonFromRpaLoader:

    archive_path: str
    inner_path: str

    def __init__(self, archive_path: str, inner_path: str) -> None:
        self.archive_path = archive_path
        self.inner_path = inner_path

    def create_module(self, spec: ModuleSpec) -> None:
        return None

    def exec_module(self, module: ModuleType) -> None:

        reader = renpy.loader.load_from_archive(self.inner_path)  # type: ignore
        if reader is None:
            raise ModuleNotFoundError(path=self.archive_path)

        module.__file__ = self.archive_path
        with reader:
            exec(reader.read(), module.__dict__)


class PythonFromRpaFinder:

    @classmethod
    def find_spec(
        cls,
        fullname: str,
        path: Union[List[str], Any, None],
        target: Optional[Any] = None,
    ) -> Optional[ModuleSpec]:

        archives: list[tuple[str, Any]] = renpy.loader.archives  # type: ignore
        inner_path_base = fullname.removeprefix("game.").replace(".", "/")

        candidate = inner_path_base + "/__init__.py"
        for archive_path, index in archives:
            if candidate in index:
                return ModuleSpec(
                    fullname,
                    PythonFromRpaLoader(archive_path, candidate),  # type: ignore
                    is_package=True,
                )

        candidate = inner_path_base + ".py"
        for archive_path, index in archives:
            if candidate in index:
                return ModuleSpec(
                    fullname,
                    PythonFromRpaLoader(archive_path, candidate),  # type: ignore
                    is_package=False,
                )

        candidate = inner_path_base + "/"
        for _, index in archives:
            files_in_archive = list(index.keys())
            if any(file_path.startswith(candidate) for file_path in files_in_archive):
                return ModuleSpec(
                    fullname,
                    DummyLoader(),  # type: ignore
                    is_package=True,
                )

        return None

setup.rpy

python early:

    import sys
    from game.load_python import PythonFromRpaFinder

    sys.meta_path.append(PythonFromRpaFinder)