fish-shell/share/functions/funced.fish

function funced --description 'Edit function definition'
    set -l editor $EDITOR
    set -l interactive
    set -l funcname
    while set -q argv[1]
        switch $argv[1]
            case -h --help
                __fish_print_help funced
                return 0

            case -e --editor
                set editor $argv[2]
                set -e argv[2]

            case -i --interactive
                set interactive 1

            case --
                set funcname $funcname $argv[2]
                set -e argv[2]

            case '-*'
                set_color red
                printf (_ "%s: Unknown option %s\n") funced $argv[1]
                set_color normal
                return 1

            case '*' '.*'
                set funcname $funcname $argv[1]
        end
        set -e argv[1]
    end

    if test (count $funcname) -ne 1
        set_color red
        _ "funced: You must specify one function name
"
        set_color normal
        return 1
    end

    set -l init
    switch $funcname
        case '-*'
        set init function -- $funcname\n\nend
        case '*'
        set init function $funcname\n\nend
    end

    # Break editor up to get its first command (i.e. discard flags)
    if test -n "$editor"
        set -l editor_cmd
        eval set editor_cmd $editor
        if not type -q -f "$editor_cmd[1]"
            _ "funced: The value for \$EDITOR '$editor' could not be used because the command '$editor_cmd[1]' could not be found
    "
            set editor fish
        end
    end
    
    # If no editor is specified, use fish
    if test -z "$editor"
        set editor fish
    end

    if begin; set -q interactive[1]; or test "$editor" = fish; end
        set -l IFS
        if functions -q -- $funcname
            # Shadow IFS here to avoid array splitting in command substitution
            set init (functions -- $funcname | fish_indent --no-indent)
        end

        set -l prompt 'printf "%s%s%s> " (set_color green) '$funcname' (set_color normal)'
        # Unshadow IFS since the fish_title breaks otherwise
        set -e IFS
        if read -p $prompt -c "$init" -s cmd
            # Shadow IFS _again_ to avoid array splitting in command substitution
            set -l IFS
            eval (echo -n $cmd | fish_indent)
        end
        return 0
    end

    set tmpname (mktemp -t fish_funced.XXXXXXXXXX)

    if functions -q -- $funcname
        functions -- $funcname > $tmpname
    else
        echo $init > $tmpname
    end
    if eval $editor $tmpname
        . $tmpname
    end
    set -l stat $status
    rm -f $tmpname >/dev/null
    return $stat
end