Can the error added in #2422 be made opt-in (or less ideally, opt-out)?

[mynewestgitaccount]

Recently (in #2422), an error was added to Starlette when Config is used without the env_file input leading to a valid file.

Until now, I would use an env file when testing locally and environment variables (without any env file) when deploying in a container. However, this change means that I either need to switch to setting environment variables locally (somewhat tedious) or to creating an env file when deploying.

Would it be possible to make this error opt-in (or even opt-out) to avoid this incompatibility? If changing this is not in the cards (or if the decision is made to make this error opt-out), I would suggest updating the documentation here, since the new error that gets raised is currently not mentioned and the documentation implies that my previous use would be acceptable.

---

Edit: Looking at the linked commits at the bottom of #2422 (after the merge/release), it seems I am not the only one affected by this.

[Kludex]

Can you show me how this part of the code looks like on your project?

[mynewestgitaccount]

The core logic looks something like this:

from starlette.config import Config

config = Config(".env")

env1 = config("ENV1")

For local development, I would use an env file named .env with the variables I needed to avoid needing to manage environment variables.
For containerized deployments, I would define the needed environment variables and would not have the .env file.

Now (following #2422), those containerized deployments fail with a FileNotFoundError.

Essentially, things have switched from "fail slow, only if lookup fails" (as described in the configuration precedence section of the documentation) to "fail fast, if a specified file is missing".

---

I understand the motivation for the change (the author described it in #2101). However, couldn't the same effect be accomplished using a default False (or even default True if needed) check_file (arbitrary name for this example) keyword argument to Config like the below?

class Config:
    def __init__(
        self,
        env_file: typing.Optional[typing.Union[str, Path]] = None,
        environ: typing.Mapping[str, str] = environ,
        env_prefix: str = "",
+       *,
+       check_file: bool = False,
    ) -> None:
        self.environ = environ
        self.env_prefix = env_prefix
        self.file_values: typing.Dict[str, str] = {}
        if env_file is not None:
-           if not os.path.isfile(env_file):
+           if os.path.isfile(env_file):
+               self.file_values = self._read_file(env_file)
+           elif check_file:
                raise FileNotFoundError(f"Config file '{env_file}' not found.")
-           self.file_values = self._read_file(env_file)

This would allow the new error to be surfaced for those who want it without requiring it for those who don't.

[Kludex]

Can you do the following?

try:
    config = Config(".env")
except FileNotFoundError:
    config = Config()

[mynewestgitaccount]

I could, but that would require a code change in any application following the previously-working (and documentation-approved) pattern. 🥲

[rambo]

I also suddenly have my docker containers failing to start after routine dependency update (obviously they use ENV directly instead of creating a .env inside). Making breaking changes should probably require a bit more discussion on the merits of breaking things that were documented as working.

[aswanidutt87]

our unit tests are failing because of this change "FileNotFoundError: Config file '.env' not found."

[Kludex]

PR welcome to replace the error by a warning.

[mathause]

I opened #2485 for this. Let me know if you want any changes.

[rambo]

Everyone is fast tonigh, also opened #2486 but it's midnight. Anyway I strongly urge that the default behaviour is what it used to be as explained in my PR and warnings would be opt-in for those who only ever use config files.

[isaackogan]

Same issue, glad it was solved.

[Kludex]

Locking this discussion to avoid spam. The "issue" was solved.