Re: Collation tests in fns-tests.el

[Eli Zaretskii <eliz@gnu.org>]

> From: Ken Brown <kbrown@cornell.edu>
> Date: Fri, 30 Oct 2015 13:51:45 -0400
> Cc: Emacs <emacs-devel@gnu.org>
> 
> I'm curious why you put the following test in fns-tests.el:
> 
> ;; Punctuation and whitespace characters are not taken into account
>    ;; for collation in other locales.
>    (should
>     (equal
>      (sort '("11" "12" "1 1" "1 2" "1.1" "1.2")
> 	  (lambda (a b)
> 	    (let ((w32-collate-ignore-punctuation t))
> 	      (string-collate-lessp
> 	       a b (if (eq system-type 'windows-nt) "enu_USA" "en_US.UTF-8")))))
>      '("11" "1 1" "1.1" "12" "1 2" "1.2")))
> 
> This suggests that punctuation and whitespace should definitely not be 
> taken into account in non-POSIX locales.

They were found to be ignored in all the cases we tested until now.

> But the docstring of 'sort' is much less definitive:
> 
> "This function obeys the conventions for collation order in your locale 
> settings.  For example, punctuation and whitespace characters *might* be 
> considered less significant for sorting."  [My emphasis.]
> 
> Is there some place where emacs relies on punctuation and whitespace 
> being ignored?

Listing of files generally ignores them, as one example.  ls-lisp.el
relies on that to emulate what 'ls' the program does on Posix hosts.

> P.S. My question is motivated by the fact that punctuation and 
> whitespace are not ignored on Cygwin in non-POSIX locales, and it does 
> not seem to be easy to make this happen.  If you're interested in the 
> gory details, start here:
> 
>    https://www.cygwin.com/ml/cygwin/2015-10/msg00516.html

You already said in that discussion what I'd suggest ;-)

Since Cygwin tries to be compatible to GNU/Linux (i.e. glibc), it
should indeed use some non-zero flags in its implementation of string
collation-dependent comparison.  IMO, it makes no sense not to do
that, since users expect that to happen.  Then the above test will
work for it, and moreover, ls-lisp.el will, too.