Required environment variables interpolation for YAML and INI files

[hakanutku]

Hi,

First of all, thanks for creating this great project. I'm using environment variable interpolation with a yaml config file. But when a environment variable is not defined and I try to access it, configuration variable is the literal value in yaml config file.

For example:
When DATABASE_URL environment variable is defined, my provided config is postgresql://postgres:password@localhost:5432/postgres
But when this variable is not defined, provided config is ${DATABASE_URL}

So is there a way to make these interpolations required? I want to throw some kind of an error if environment variable is not set.

[rmk135]

Hi @hakanutku ,

So is there a way to make these interpolations required?

No, there is no way to make it right now.

I think this is a reasonable problem. Thanks for bringing this up. I'll think how I can address this.

[hakanutku]

Hi @rmk135,

Thanks again for the response. This api solves my problem. But I think when envs_required parameter is set to False, from_* methods should load env interpolations as None and not the literal value if the environment variable is not set. I don't think this would be a breaking change for the existing users. But I'm not sure.

[rmk135]

But I think when envs_required parameter is set to False, from_* methods should load env interpolations as None and not the literal value if the environment variable is not set. I don't think this would be a breaking change for the existing users. But I'm not sure.

I tend to agree. I looked onto other yaml parsers in various systems and none of them leave environment variable markers unreplaced. I'm going to implement the same in Dependency Injector.

[rmk135]

@hakanutku I released version 3.44.0 that adds envs_required argument and interpolates undefined environment variables to empty value. For more information please check this documentation section: https://python-dependency-injector.ets-labs.org/providers/configuration.html#using-environment-variables-in-configuration-files

Also I've added raising of an exception on undefined environment variables for configuration provider in strict mode. Strict mode is described here: https://python-dependency-injector.ets-labs.org/providers/configuration.html#strict-mode-and-required-options

You can find full release notes in changelog: https://python-dependency-injector.ets-labs.org/main/changelog.html

Many thanks for raising this question. Also let me know if you have any other improvements. Would be glad to hear that.

[hakanutku]

This implementation covers all possible use cases and documentation is clear. I will upgrade to this version asap. Thanks again for the quick response and action.

[rmk135]

Thank you for bring up the use case. Let me know if anything else pops up - I'll be glad to help.