Re: Question about test failure on Hydra

[Eli Zaretskii <eliz@gnu.org>]

> From: Stephen Berman <stephen.berman@gmx.net>
> Date: Sun, 30 Jul 2017 17:50:38 +0200
> 
> (ert-deftest dired-test-bug27243-01 ()
>   "Test for https://debbugs.gnu.org/cgi/bugreport.cgi?bug=27243#5 ."
>   (let ((test-dir (make-temp-file "test-dir-" t))
>         (dired-auto-revert-buffer t) buffers)
>     (with-current-buffer (find-file-noselect test-dir)
>       (make-directory "test-subdir"))
>     (push (dired test-dir) buffers)
>     (unwind-protect
>         (let ((buf (current-buffer))
>               (pt1 (point))
>               (test-file (concat (file-name-as-directory "test-subdir")
>                                  "test-file")))
>           (write-region "Test" nil test-file nil 'silent nil 'excl)
>           ;; Sanity check: point should now be on the subdirectory.
>           (should (equal (dired-file-name-at-point)
>                          (concat (file-name-as-directory test-dir)
>                                  (file-name-as-directory "test-subdir"))))
> 
> When it fails, Hydra show dired-file-name-at-point returning e.g. this
> (it's a temporary directory so the name is different on each test run):
> 
> "/build/test-dir-26691mMc/../"
> 
> while the concat sexp it's being compared with returns (e.g.) this:
> 
> "/build/test-dir-26691mMc/test-subdir/"
> 
> IIUC dired-file-name-at-point can only return the above result if point
> is on the ".." entry in Dired.  But the sexp (dired test-dir) should
> (and in all my test runs does) put point on the first "nontrivial" file
> (i.e. it skips "." and "..").  I don't see how the above code can lead
> to the failure Hydra reports.  And again, it doesn't always fail in
> Hydra.  Does anyone have any idea what's going on here and what to do
> about it?

Doesn't dired-auto-revert-buffer by default use some kind of file
notifications?  If so, this could be some race between the
notification coming in and the rest.  You could introduce a wait to
try to solve that, or maybe try turning off file notifications.