EnvSettingsSource get_field_value returns field_name instead of the env name.

[atti92]

In 2.7.0 get_field_value returns the field_name instead of the env name, we depended on this logic, but now it makes it really hard to figure out which environment variable was used.

Can we have the env_name added back to EnvSettingsSource to look up the value?

I can see why the change was made, and it makes sense, but we are loosing data with it. We were using it to give feedback for users to track each configuration's value's source. eg.: conf.value1 -> $MY_ENVVAR, conf.value2 -> .env/VALUE2, etc...

Code block in question:

        for field_key, env_name, value_is_complex in field_infos:
            env_val = self.env_vars.get(env_name)
            if env_val is not None:
                if value_is_complex or (self.config.get('populate_by_name', False) and (field_key == field_name)):
                    preferred_key = field_key
                break

        return env_val, preferred_key, value_is_complex

We are also fine if env_name is saved somewhere inside the class to lookup later.

[hramezani]

Thanks @atti92 for reporting this issue.

@kschwab can you take a look?

[kschwab]

@atti92, great catch, thanks for the issue. I'll update the API to include a "use_preferred_alias" flag that could be used to distinguish between the two, e.g.:

get_field_value(self, field: FieldInfo, field_name: str, use_preferred_alias: bool = False)

When set to True, the env name returned will be the preferred alias env name. Otherwise, it will return the raw env name that was found. I'll set the default to False to restore backwards compatibility.

@hramezani, if the above API change is considered breaking, we could also modify to keep the alias resolution strictly internal. Let me know what you would like.

I opened #507 as current solution.

[hramezani]

Thanks @kschwab for the PR.

The PR will introduce a breaking change because it changes the signature of get_field_value.

[kschwab]

Sure @hramezani. Would you like me to create a new public API for environment sources, e.g., get_resolved_field_value, that returns the preferred alias key, or just keep the resolution private?

[hramezani]

let's not introduce a new API for now and keep it private.

But it would be good to add a comment for the future. we might change it in V3

[kschwab]

I restored the original get_field_value behavior and moved the alias resolution into a private method. If desired it can be made public in V3.

[hramezani]

The fix has been released on pydantic-settings 2.7.1