Expanding nix-shell prompt segment to include inputs

[presto8]

Currently, p10k will display the nix logo and either pure or impure based on the environment variable IN_NIX_SHELL, which is set by nix-shell.

Example segment: * impure

nix-shell also sets the environment variable buildInputs, for example:

buildInputs=/nix/store/f6cgapys8iaafbh0fn83j562l1vrgcmh-inxi-3.3.04-1 /nix/store/w6q900b5kazwj4j8mhgsdqy4z1q2cbwx-dmidecode-3.5

It is pretty easy to split off the build inputs and add them to the segment:

Example proposed segment: * impure inxi-3.3.04-1 dmidecode-3.5

The version number at the end could be stripped off as well.

Is this something of interest and is it acceptable performance-wise to include in the code p10k code? I feel it is pretty useful information to have when running a nix-shell. I could prepare a pull request, but wanted to gauge interest first.

Rough parsing code:

    inputs=()
    for entry in ${=buildInputs}; do
        suffix=${entry#/nix/store/*-}
        inputs+=( "$suffix" )
    done

Thank you!

[romkatv]

I'm concerned that the list of build inputs can be arbitrarily long, and perhaps in practice it does indeed happen to be very long on occasion. I'm leaning towards having just "impure" to indicate the presence of those build inputs. Users can query additional details manually. This is similar to the git segment showing just the number of modified files but not the actual files names. Come to think of it, would it be helpful to include the number of build inputs next to "impure"?

[presto8]

Good points! At least in my use, I normally only have 1 or 2 build inputs, but I could see how others might have more. It could be a configuration variable, "display at most X" and then the rest go in a counter. Also I think the version needs to be stripped off.

So nix-shell -p vlc -p mpv -p id3v2 -p beets might result in:

impure vlc mpv id3v2 beets (no limit)
impure vlc mpv +2 (limit of 2 plus counter)
impure +4 (counter only)

[romkatv]

You can implement it as a custom prompt segment. I'm not sure it's super useful in the core p10k.

[presto8]

No problem, I kind of figured that might be the case. I already did it as a custom prompt for myself and found it very useful which is why I thought others might be interested :)