bug#21816: elisp-mode-tests fails on a case-preserving filesystem

[Eli Zaretskii]

> From: Stephen Leake <stephen_leake@stephe-leake.org>
> Cc: lekktu@gmail.com,  21816@debbugs.gnu.org
> Date: Tue, 03 Nov 2015 13:24:31 -0600
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Sorry to bust this party, guys, but I don't think this solution is
> > "good enough".  
> 
> In general, or just for this test?

Both, IMO.

> Let's fix the test first, and worry about the general case later.

Why not kill two birds with the same stone?

> > First, it won't DTRT with Windows file names that have
> > backslashes (yes, they happen in Emacs).  
> 
> That's easy; add `expand-file-name'.

For this specific case, yes.  But there's no way to be sure no one
will ever use concat or some such.  Or just take default directory and
use it directly.

> > Second, 'downcase' has a known gotcha of using the current buffer's
> > case tables, which is something you definitely don't want here.
> 
> Ah; I had not considered non-ASCII stuff.
> 
> Is there some global variable we can let-bind to control that?

You want with-case-table and standard-case-table, I think.

> > Bottom line, doing this "right" is not so trivial, and a dedicated
> > function is a better solution, IMO.  If you put it in files-x.el, it
> > could be reused by other Lisp programs in the need of this.
> 
> Yes, that makes sense.
> 
> > IME, it doesn't pay off to use such incomplete solutions, the result
> > is an annoying, albeit minor, maintenance burden.  
> 
> Not in this test.

Not today, maybe.  But there's always tomorrow and the day after.