fish-shell/share/functions/__fish_complete_mount_opts.fish

function __fish_print_user_ids
    if command -sq getent
        for line in (getent passwd)
            set -l v (string split : -- $line)
            printf "%s\t%s\n" $v[3] $v[1]
        end
    end
end

function __fish_print_group_ids
    if command -sq getent
        for line in (getent group)
            set -l v (string split : -- $line)
            printf "%s\t%s\n" $v[3] $v[1]
        end
    end
end

function __fish_complete_mount_opts
    set -l fish_mount_opts\
    async\t'Use asynchronous I/O'\
    atime\t'Update time on each access'\
    noatime\t'Do not update time on each access'\
    auto\t'Mounted with'\
    noauto\t'Not mounted by -a'\
    defaults\t'Use default options'\
    dev\t'Interpret character/block special devices'\
    nodev\t'Do not interpret character/block special devices'\
    diratime\t'Update directory inode access time'\
    nodiratime\t'Don\'t update directory inode access time'\
    dirsync\t'Use synchronous directory operations'\
    exec\t'Permit executables'\
    noexec\t'Do not permit executables'\
    group\t'Any user within device group may mount'\
    iversion\t'Increment i_version field on inode modification'\
    noiversion\t'Don\'t increment i_version field on inode modification'\
    mand\t'Allow mandatory locks'\
    nomand\t'Don\'t allow mandatory locks'\
    _netdev\t'Filesystem uses network'\
    nofail\t'Don\'t report errors'\
    relatime\t'Update inode access times'\
    norelatime\t'Don\'t update inode access times'\
    strictatime\
    nostrictatime\
    lazytime\
    nolazytime\
    suid\t'Allow suid bits'\
    nosuid\t'Ignore suid bits'\
    silent\
    loud\
    owner\
    remount\t'Remount read-only filesystem'\
    ro\t'Mount read-only'\
    rw\t'Mount read-write'\
    sync\t'Use synchronous I/O'\
    user\t'Any user may mount'\
    nouser\t'Only root may mount'\
    users\t'Any user may mount and unmount'\
    protect\
    usemp\
    verbose\
    {grp,no,usr,}quota\
    autodefrag\
    compress\
    compress-force\
    degraded\
    discard\
    enospc_debug\
    flushoncommit\
    inode_cache\
    context=\t'Set SELinux context'\
    uid=\
    gid=\
    ownmask=\
    othmask=\
    setuid=\
    setgid=\
    mode=\
    prefix=\
    volume=\
    reserved=\
    root=\
    bs=\
    alloc_start=\
    check_int{,_data,_print,_mask}=\
    commit=\
    compress=\
    compress-force=\
    device=\
    fatal_errors=\
    max_inline=\
    metadata_ratio=\
    noacl\
    nobarrier\
    nodatacow\
    nodatasum\
    notreelog\
    recovery\
    rescan_uuid_tree\
    skip_balance\
    nospace_cache\
    clear_cache\
    ssd\
    nossd\
    ssd_spread\
    subvol=\
    subvolrootid=\
    thread_pool=\
    user_subvol_rm_allowed\
    acl\
    noacl\
    bsddf\
    minixdf\
    check=none\
    nocheck\
    debug\
    errors={continue,remount-ro,panic}\
    grpid\
    bsdgroups\
    bsdgroups\
    bsdgroups\
    nouid32\
    grpquota\
    grpquota\
    resgid=\
    resuid=\
    sb=\
    {user,nouser}_xattr\
    journal={update,unum}\
    journal{_dev,_path}=\
    norecovery\
    noload\
    data={journal,ordered,writeback}\
    data_err={ignore,abort}\
    barrier={0,1}\
    user_xattr\
    acl\

    set -l token (commandline -tc | string replace -r '^-o' -- '')
    set -l args (string split , -- $token)

    if test (count $args) -ne 0
        set -l last_arg $args[-1]
        set -e args[-1]

        switch (string replace -r '=.*' '=' -- $last_arg)
            case uid=
                set -a fish_mount_opts uid=(__fish_print_user_ids)
            case gid=
                set -a fish_mount_opts gid=(__fish_print_group_ids)
            case setuid=
                set -a fish_mount_opts setuid=(__fish_print_user_ids)
            case setgid=
                set -a fish_mount_opts setgid=(__fish_print_group_ids)
        end
    end

    set -l prefix ''
    if set -q args[1]
        set prefix (string join , -- $args),
    end

    printf '%s\n' $prefix$fish_mount_opts
end