Re: problem with context specification

["Daniel Shahaf" <d.s@xxxxxxxxxxxxxxxxxx>]

Pier Paolo Grassi wrote on Tue, 14 Jan 2020 15:59 +00:00:
> to answer Daniel:
> 
> > I take it the documentation of zstyle didn't make this clear, so could you
> > suggest how to improve it?
> 
> It's not clear to me what is the meaning of the various "sections"of the
> pattern (the segments delimited by the colons)

This, too, is explained in the manual (see zshcompsys(1), or online):

       The context string always consists of a fixed set of fields, separated
       by colons and with a leading colon before the first.  Fields which are
       not yet known are left empty, but the surrounding colons appear anyway.
       The fields are always in the order
       :completion:function:completer:command:argument:tag.  These have the
       following meaning:

> what should I put in the first section?

":completion:", literally.  That's hard-coded.  See the patch I posted
for another example, and Misc/vcs_info-examples in the source
distribution.

> is there a list of possible values and relative meaning?

The manual does list the available completers and many tags and styles (the style
is, e.g., "matcher-list" in your example), but it's possible some commands use custom
ones.  Ctrl+X h is the standard recommendation for discovering these.

> and so on for each section
> why the number of sections is not the same for every pattern?

Because asterisks can match colons.  The number of sections in the
context _that is looked up_ (with zstyle -s/-t/-T/-b/-a) is always the
same.  There's an example in the patch I posted.

> How can I know how many pattern I should put in?

One pattern per zstyle command in your zshrc.

If you mean how many colon-separated parts, that's up to you.  It's
basically a matter of coding style unless you set the same style in
multiple contexts, in which case the colons directly affect precedence,
as explained in the portion of the docs I quoted in my first answer
(though in retrospect I'm not sure now if that was what you were asking
about then).

> I assume the stars are for matching every possible value for that segment,

No.  An asterisk matches zero or more characters, _including colons_.
(My patch said that explicitly.)

> are there other globbing operators available?

Yes, anything that works in «case $haystack in ‹needle›) …;; esac», or
equivalently in «[[ ‹haystack› == ‹needle› ]]», can be used in zstyle settings.

> can I use them for prefix/suffix matching? (eg someth* for
> something etc)

Yes, you could:

% zstyle 'foob*' key value
%                           
% zstyle -s foobar key REPLY 
% typeset -p REPLY
typeset REPLY=value
% 

For example, I set:

zstyle ':completion:*:*:git-*:*:hosts' ignored-patterns localhost ip6-localhost ip6-loopback

and the style applies to git-push(1), git-pull(1), git-ls-remote(1), etc..

> Not that I think it would be particularly useful, but the question
> came to mind I assume also that the stars don't match multiple
> segments, but this doesn't seem to be stated in the docs.

See above.