Re: Tags in function files

[Bart Schaefer <schaefer@brasslantern.com>]

[reordering things a little ...]

On Sep 17,  9:37pm, DervishD wrote:
>
>     My problem with the compsys documentation is that I don't know
> which parameters, tags and the like are defined by compsys and which
> ones are controled by Zsh guts ;)) I'm learning, slowly but surely ;)

If it's in "man zshcompwid" (info doc, Completion Widgets section) then
it's an internal parameter.  If it's in "man zshcompsys" (Completion
System section) then it's created by _main_complete or one of the helper
functions it calls.

Nearly all the parameters that you're supposed to access directly are
internal; parameters of compsys are mostly "hidden" behind zstyles, or
commands such as compdef.

Conversely, all zstyles, tags, etc. are defined by compsys.  There are
no internally-defined tags.  (There are several builtins to manipulate
them [for speed], but you're not supposed to need to know that.)

So if you're not using compinit, you can ignore anything that's said
about styles and tags.

>     OK, now all makes sense. I was testing with a dummy widget (NOT a
> completion one...) and I was able to use 'zle complete-word' inside
> my widget, but I couldn't use '$words' (it expanded to nothing). On
> the other hand, I created a dummy completion widget with zle -C but
> then I wasn't able to use the predefined widgets inside.

Right.  ZLE is separate from the collection of completion modules.  When
a completion widget is invoked, zsh/zle gives control to zsh/complete,
and won't accept control back again until the completion widget returns.
Thus you can begin a completion from a normal widget, but you can't call
back to a normal widget from a completion.  (The normal widget can keep
going after the completion finishes, but that's something different.)

However, please note that there are no predefined completion widgets!

There are only predefined completion _behaviors_ which happen to be
described by a set of widget names.  The competion widgets that _used_
to be predefined are now supplied by the zsh/compctl module, which has
to be loaded in order for those widgets to do anything.

As it turns out, if you attempt to use completion without first defining
at least one widget, zsh automatically loads zsh/compctl just so that
something sensible will happen.  The illusion of predefined completion
widgets is maintained, but it really is an illusion.

> Namely something like this:
> 
> my_comp () {
>     zle .complete-word
> }
> 
> zle -C dummycomp complete-word my_comp

This sort of thing is why "compcall" (from the zsh/compctl module) is
provided.  You want:

    zmodload -i zsh/compctl
    my_comp () {
	compcall -D
    }

The behavior of "compcall" is selected by the 2nd argument of "zle -C";
you can't switch from complete-word to expand-or-complete in midstream
(except in so far as poking into the compstate parameter allows).

> I would like to be able to last-resort to some
> predefined completion widget, or even call some zle widget to move
> the cursor, retrieve the story, clean the command line, etc... That
> is, using some of the zle facilities inside my completion widget.

Unfortunately you can't do the latter of those directly from within
the completion widget.  What you can do, I believe (having never tried
it myself), is something like this:

    my_comp_wrapper () {
	local some_variable_set_by_my_comp_on_failure
	zle dummycomp	# Invoke your completion, let it return
	if [[ -n $some_variable_set_by_my_comp_on_failure ]]
	then
	    # move the cursor, retrieve the story, clean the command line
	fi
    }
    zle -N my_comp_wrapper
    bindkey '^O' my_comp_wrapper

Just remember NOT to declare some_variable_set_by_my_comp_on_failure as
a local in my_comp.  You want it to modify its caller's local.