Fish Shell: Expand 'run' to an appropriate 'run' command, depending on the files in the current directory.

run.fish

function _expand_run
    -d "Expand the 'run' abbreviation into a project-specific run command.";
    if test -e Justfile;
        echo just run
    else if test -e Makefile;
        echo make run
    else if test -e Cargo.toml
        echo cargo run
    else if test -e package.json
        echo npm run dev
    end
end

abbr --add run --function _expand_run;
abbr --add r --function _expand_run;