Allow to override an array field / nested property

[sschuberth]

          > I guess we could support `databases[1]__port = 9301` ?

I'd still be interested to override single properties within a list of a config read from a file via CLI options like that, without the need to declare "placeholder properties" that refer to environment variables. Is something like that supported by now?

Originally posted by @sschuberth in #144 (comment)

[sschuberth]

More specifically, it would be great if MapPropertySource and CommandLinePropertySource would support the "key" to contain an index like [1] to be able to override single values nested within an array list. (Even is that value was not present originally, so it's more "add" than "override"; in that aspect this issue is different from #144, where you can work with environment placeholders.)

[sschuberth]

@sksamuel I'm willing to work on this, but I have no clue where to start. Is my approach outlined above even feasible to implement?

[sksamuel]

I think your approach for map property source and cli property source are perfectly reasonable.
We already do something some what similar in the aws preprocessor with [] used for json fields.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[sschuberth]

While I didn't have time to work on this yet, I believe it still makes sense as a feature to add.

[sschuberth]

aws preprocessor with [] used for json fields.

Maybe by now https://github.com/eygraber/JsonPathKt could be leveraged...

[sksamuel]

Not sure we even need that. Just need to take [n] and apply that to the list ?

[sschuberth]

Not sure we even need that. Just need to take [n] and apply that to the list ?

For lists you're probably right. But we basically have the same issue also for overriding values in a map. And there, in order to refer to the key's name in the map, maybe JsonPathKt would be helpful.