RFC: autocomplete newest file in directory

[compholio]

Some time ago I put together a modification to _filedir to allow autocomplete to return the latest file in a directory. I've found this to be incredibly useful, so I've put together a fork with these changes:
https://github.com/compholio/bash-completion
Examples:

mv ?<TAB> -> mv latest-file.pdf
mv ~/Downloads/?<TAB> -> mv ~/Downloads/latest-file.pdf

I'd be curious to see how others feel about this and whether people think this feature (or a version of it) is worth including in bash-completion.

[scop]

I don't remember missing such a feature myself. It can surely be useful in some use cases and workflows, but then again so could be completing with the oldest/smallest/largest/random/first-sorted/last-sorted one. And offhand I think more often than not we should respect the globs for completing these special cases so that e.g. for a PDF viewer one would get the newest/oldest/... PDF. I guess I find the idea interesting, but there are so many variables at play that I'm not sure an easy enough to use implementation exists.

[compholio]

Is there an easy way to communicate a different keystroke to bash-autocomplete? It could make sense to bind a keystroke (similar to menu-complete) and then we could know to complete something like mv ~/Downloads/*.pdf<SHIFT-TAB> to the latest pdf. It appears to me that complete and menu-complete are bash builtins and that there's not a way to define a "latest-complete" and have it call the regular complete.

I ask because the closest I've been able to get to calling bash-completion from a keybinding is something that looks like this (and it's not perfect):

bind -x '"\e[Z":latest-complete'

latest-complete() {
    local COMP_LINE COMP_WORDS COMP_POINT COMP_CWORD routine COMPREPLY=()
    COMP_LINE="${READLINE_LINE}"
    COMP_WORDS=(${COMP_LINE})
    COMP_POINT=${READLINE_POINT}
    COMP_CWORD=$((${#COMP_WORDS[@]}-1)) # this needs to find the current word based on the COMP_POINT
    routine=$(complete -p "${COMP_WORDS[0]}" | cut -d' ' -f3)
    "${routine}"
    COMP_WORDS[${COMP_CWORD}]=$(printf '%q\n' "${COMPREPLY[@]}" | sed 's/\\~/~/')
    READLINE_LINE=$(echo "${COMP_WORDS[*]// /}")
    READLINE_POINT=${#READLINE_LINE}
}

[compholio]

I think that I've found another way to approach this that might be more reasonable. New bash binding:

bind -x '"\C-t1":COMP_LATEST=1'
bind '"\C-t2":complete'
bind -x '"\C-t3":unset COMP_LATEST'
bind '"\e[Z":"\C-t1\C-t2\C-t3"'

Then inside _filedir we can use COMP_LATEST to split the path and override xspec such that, for example, ls ~/Downloads/*.pdf<SHIFT-TAB> will return the latest PDF. How does that sound?