Multi-part configurations

[spacekookie]

Should it be possible to have a global config that is overwritten by a local/ user config, etc. And how would be the best way to implement this?

Suggested by #2 (comment)

[gibix]

default in: $HOME/.$BINARYNAME.$EXTENSION overrided by an Option<Path>

This sounds good?

struct Confy {
    cfg_in: Option<Path>,
    cfg_out: Option<Path>,
}

impl Confy {
    new(cfg_in, cfg_out) -> Confy... // if cfg_in.is_none() check for default
    load...
    write...
}

[Dylan-DPC-zz]

@gibix looks good but do we need to make the inputs optional?

[gibix]

Confy { None, None } maps to default values

[kamalmarhubi]

Please use app_dirs or one of the replacements for the default config path. (I forget which is the "most bestest" at the moment.)

I think it's well worth surveying how different systems handle this. If this is going to be a default suggestion for how to handle config, it should not do anything "objectionable". In this case, I would call using $HOME/.something objectionable: many people will object and say it should put stuff in $HOME/.config/something ($XDG_CONFIG_HOME) or $HOME/Library/...` on Mac.

For example, a typical binary on my (Debian) system will look for files under these directories:

• vendor provided defaults (ie from author or packager) in /usr/share/something
• system defaults (for sysadmin to use) /etc/something
• somewhere in home (for each user)—either $HOME/.something or $XDG_CONFIG_HOME/something depending on how well behaved

Individual settings in each location override the previous locations, so that all files are read in order, and configurations are updated.

[kamalmarhubi]

Also in #3 (comment), the subject of this issue was pointed out as a non-goal:

Absolute non-goals would for example be: [...] a comprehensive feature list like having multiple config files where fields from one overwrite fields in another.

I don't have strong feelings on whether it's in scope or not for a crate like confy, but I do have strong feelings on doing it right if it ends up being included.