lib/generators: add toKeyValue & mkKeyValueLine

[Profpatsch]

generators for the common use case of simple config files which hold keys and
values. Used in the implementation for toINI.

• three new unit tests that pass, old tests pass as well

Can be used in #20888 directly.

[mention-bot]

@Profpatsch, thanks for your PR! By analyzing the history of the files in this pull request, we identified @edolstra, @MarcWeber and @zagy to be potential reviewers.

[vcunat]

Seems OK, at a superficial look.

[edolstra]

Can't this be renamed to mkIniFile or something like that? ...KeyValue says absolutely nothing.

[Profpatsch]

Can't this be renamed to mkIniFile or something like that?

Ah, it creates a key-value config file, toINI generates the ini files.
Hm, but not sure what a better name for that would be; maybe improve the docs?

The generators themselves are named toX, the exported helper functions mkX. All generators have the same calling convention (first argument configuration, second the data). Maybe the helpers should use a different naming scheme?

[vcunat]

mkKeyValueLine function is very general, so it seems hard to come with a more concrete name. If it's unlikely to be used from a different file, we might hide it in a let at the top.

[Profpatsch]

If it's unlikely to be used from a different file, we might hide it in a let at the top.

Well, it’s used in the default implementation of the mkKeyValue config options, mkKeyValueLine "=". On second thought, it should probably be named mkKeyValueDefault instead, since Line sounds like it ends with \n .

[Profpatsch]

I have renamed the function in #20920