Make rc2nix stable

[luochen1990]

Hi, I find that currently rc2nix is not stable, which means, when I run rc2nix and activate it and run rc2nix again, things changed.

Here is the diff between run rc2nix first time and second time:

I hope to make it stable. And so have several questions:

1. I find that there is also KConfManager.read() in write_config.py which parse config files just as what rc2nix.py did, is it possible to lift the config file parsing logic into a common utils to reuse them? (we can also do similar thing for unparse so that we can add unit tests to make sure they are inverse functions of each other.)
2. Is this a bug? I need some detailed explanation for the diff in the pictures above.

[HeitorAugustoLN]

I am thinking of moving every script to a single cli program, since I'm going to be adding another script for kxmlgui files, so they can also share utilities, because i think KConfManager.read() could be actually used for rc2nix, but I will need to look into it.

[robert-elles]

Hey,
as a workaround I have a script that validates the syntax of the output that rc2nix produces and removes the problematic lines:

file=~/yourfile/plasma_rc2nix.nix

rc2nix > $file

while true; do
    result=$(nix-instantiate --parse $file -v 0 --log-format internal-json 2>&1)
    result=$(echo "$result" | sed 's/.*@nix.*@nix//')
    result=$(echo "$result" | sed 's/^@nix//')
    
    line=$(echo "$result" | jq -r '.line' | sed '1d')

    if [ -z "$line" ]; then
        break
    fi

    echo "removing line: $line"
    sed -i "${line}d" $file
done