Provide a feature for auto-binding from JVM and env variables

Rationale Having worked with Spring Boot’s excellent configuration management, I really miss the benefits in Scala. I’d like to propose a new feature that I think will cut down the boilerplate a lot, thus making pureconfig even more awesome 😄 and reduce chances of user error.

Proposal For every property in that’s being bound -

• Convert to env var format (foo.barIsCool will become FOO_BAR_IS_COOL), and look up in the env vars. If present, those will override application.conf and any default in code.
• Look up as-is (no conversion) in the JVM variables. If present, those will override env var, application.conf and any default in code.

The above can be made available as a new hint that the users can choose. Also,

• Allow comma-separated strings to be treated as Iterable. Overriding each elements of the list from command line is simply waste of time.

[nigredo-tori]

Sorry for digging up this old issue, but it has come up in an internal discussion at my workplace, and I figured it wouldn’t hurt to provide a little update.

While a lot of the proposed features are difficult to implement, one cheap thing we can do is add support for injection through environment variables (albeit without mangling names). So we can have PREFIX_foo.barIsCool environment variable being treated as a candidate for the foo.barIsCool config value.

The implementation for the above should be relatively simple. Just take sys.env, filter/strip (configurable) key prefix as desired, pass to ConfigFactory.parseMap, and wrap the result as a ConfigSource. That ConfigSource can then be inserted into the ConfigSource stack.

I don’t think this should be a part of the default ConfigSource stack, and I’m not sure this pattern is even common enough to provide the described ConfigSource builder as a part of the library itself, but at the very least this is now achievable.

[nigredo-tori]

shells only support alphanumeric characters and underscores

Sorry, I haven’t taken this into account. This means that we would still need some kind of mangling - probably something like what happens to CONFIG_FORCE_ variables.