Enhance Starlette Config with fastenv

[br3ndonland]

Description

Starlette offers a Config model for managing settings related to a Starlette application.

This model is simple and useful, but has some limitations.

One of the issues with the Starlette Config model is that it can only load a single .env file (encode/starlette#432).

Another issue is that, if the .env file is not found, Starlette fails silently instead of raising an exception. Applications often depend on environment variable values to function properly, so without an exception, the application may start up and behave unexpectedly.

fastenv could be used to enhance the functionality of the Starlette Config model.

Suggestions

Add Starlette as an optional dependency

Add Starlette as an optional dependency in pyproject.toml.

Enhance the Starlette Config model with fastenv

Add a subpackage fastenv.settings.

Add a module fastenv.settings.starlette_config that imports starlette.config and overrides its __init__() and _read_file() functions with logic from fastenv.

Rough suggestion:

from typing import TYPE_CHECKING, Sequence

import anyio
import starlette.config

from fastenv.dotenv import load_dotenv

if TYPE_CHECKING:
    from os import PathLike


class Config(starlette.config.Config):
    def __init__(
        self,
        env_file: Sequence[PathLike[str] | str] | PathLike[str] | str | None = None,
        environ: dict[str, str] = starlette.config.environ,
        *,
        raise_exceptions: bool = True,
    ) -> None:
        self.environ = environ
        self.file_values: dict[str, str] = {}
        if env_file:
            env_file_values = (
                self._read_file(*env_file)
                if isinstance(env_file, Sequence)
                else self._read_file(env_file)
            )
            self.file_values |= env_file_values

    def _read_file(self, *files: PathLike[str] | str) -> dict[str, str]:
        dotenv = anyio.run(load_dotenv, *files)
        return dict(dotenv)

Export the Starlette Config model

Add the model to fastenv.__init__ to export it.

Related

• fastenv docs: comparisons - Starlette
• Multiple .env files for Config encode/starlette#432