bug#63896: [PATCH] Support annotating and sorting the project list during completion

[Eli Zaretskii <eliz@gnu.org>]

> From: Spencer Baugh <sbaugh@janestreet.com>
> Cc: 63896@debbugs.gnu.org
> Date: Tue, 13 Jun 2023 17:19:52 -0400
> 
> >> +          (cons (+ (* 100 compilation-num-errors-found)
> >> +                   (* 10 compilation-num-warnings-found)
> >
> > Why "encode" these numbers in a single value? why not use a cons or a
> > vector?
> 
> I'd be happy to use a cons or a vector, or even a more complicated
> structure, but I didn't see an easy way to do comparison of
> complicated structures, for the sorting of projects based on their
> annotation.  For example, if I have values of the form
> (num . (num num num))

You'd need to write a custom comparison function, but why is that a
problem?

> there's no way to know what sorting predicate to use for such values - I
> need to be able to know which value should sort sort first, when I have
> a pair of them.

But the encoding scheme above provides the answer: you want errors to
sort before the warnings.  So it sounds like you already decided how
to sort those, no?

> >> +                (format-mode-line mode-line-process nil nil buf)))
> >
> > Do you really need to call format-mode-line?  My advice is to stay
> > away of that function: it could have unpleasant side effects.
> 
> Annoyingly if I want to include the exit code of the compilation in the
> annotation, the only place it's found is as a string in
> mode-line-process.  I could extract that string from mode-line-process
> and use it, but I thought it would be a bad idea to depend on the exact
> structure of what compile.el puts in mode-line-process.  So I just
> format-mode-line'd it.
> 
> Would it be OK to make compile.el store the exit code as a number in a
> variable and then use that?  Then I wouldn't need to touch
> mode-line-process at all.

I don't see why you'd need that.  Doesn't process-exit-status give you
that value?  mode-line-process is not some magic, it just accesses
process information exposed via the different primitives.