[Bash-completion-devel] misc: compgen, colors, comp interruption

[Raph]

Hi !
Some ideas in bulk about bash completion, mostly about colors.

Colors:

Q) how to grab them ?
A) in ls.c, which parse LS_COLORS, ls --color=always
Until it is implemented as a library, /bin/ls can be used.
(binutils sources is the only place I found where DIR_COLORS parsing
happens)
 
Since I discovered that compgen -W can handles colorized output well, quoting
is the "first" issue I can see.

eg:
touch "a1.mpg" "a2.tar" "b 3.mpg" "c\\4.tar"

$ compgen -W "$(ls --color=always a*)"
completes well with colors
$ compgen -W "$(ls --color=always *)"
splits "b 3.mpg" and trims the backslash of c\4.tar
$ compgen -W "$(ls -b --color=always)"
completes all files well with colors

So now, in the script attached:
- if we use the COMPREPLY n°1, we notice a problem with
$IFS: (filename with space = 2 elements in COMPREPLY[])

But other than that, let's use the completion n°2 and 3:
COMPREPLY=( $( compgen -W "$(ls --color=always ${cur}*)" ) )
comptest a<TAB>
The line is transformed.

So the next question seems to be: how to dissociate the string under the
cursor from the string under the line (I used to call "suggestion")
On this subject:
http://www.mail-archive.com/bash-completion-devel@lists.alioth.debian.org/msg00786.html

http://groups.google.com/group/gnu.bash.bug/browse_thread/thread/532fcafba753a281/a155819450baae2f
http://groups.google.com/group/gnu.bash.bug/browse_thread/thread/cc79f1be05d7318e/6493a1c2644d7e8f
Chet speaking about the "visible-stats" readline variable.
It makes me think that colors should really be implemented at the readline level.
Perl, python or mysql shell users may really benefit from colors.

http://groups.google.com/group/gnu.bash.bug/browse_thread/thread/ff22232f56f33445/72225aee50272f8d
about readline hooks.

Some example of what I would see offered in a flexible readline completion:
- ability to display colorized filenames
- ability to display option summary while <tab>ing for options list
- ability to display progress bar while completing with filenames
- ... maybe more

IMHO: the "right way" would be:
- a libdircolors which readline would link against
- a colors -o option to compgen usable with -o filenames
(like the inputrc/bind visible-stat)

I'm quite sure it needs a patch in libreadline + at least 1 other $COMP* variable
to be considered by bash + a inputrc option.
This $COMPX variable may be an associative array like
[word_to_complete_with] => [word_to_use_to_display_suggestion]
But still it doesn't really offer the flexibility of suggestion.
Or COMPREPLY_PRE(string), COMPREPLY_POST(string) and COMPREPLY_ASSOC
(assoc mentioned above)
...


While I'm speculating on this, I would like to speak about the ability
to interrupt the completion process:

Because today there are more and more completions we can not assure that
all of them resolve in an acceptable time.
Eg, while adding, to the cmdline, a long list of file paths, each <tab>
is now considering the whole cmdline taking quite some time (some
seconds with 20 files) and I ended up in using Alt+/.

The same applies to emerge, apt-get, ssh, ...
I still think that considering a Ctrl+g to interrupt completion is a
workaround for deeper problems but this need may come sooner than we
would want.

As I'm throwing ideas here, I would like to know what you, bashcomp
hackers, think about these subjects ?


sorry for such a long oration.

Raph
-------------- next part --------------
# bash completion for test
_comptest()
{
    local cur

    COMPREPLY=()
    _get_comp_words_by_ref cur
# ex1
    COMPREPLY=( $( compgen -f -- "$cur" ) )

# ex2: no completion ($cur starts with a character, wordlist elements contains shell-color-escape character)
#    COMPREPLY=( $( compgen -W "$(ls --color=always ${cur}*)" -- "$cur") )

# ex3: completion problem: in line $cur is replaced with the shell-color-escape character
# because we omit -- $cur and the common prefix is the color
# It would not complete anything if all colorized filename are of different color
#    COMPREPLY=( $( compgen -W "$(ls --color=always ${cur}*)") )

} &&
complete -F _comptest -o filenames comptest

# Local variables:
# mode: shell-script
# sh-basic-offset: 4
# sh-indent-comment: t
# indent-tabs-mode: nil
# End:
# ex: ts=4 sw=4 et filetype=sh