Re: File watch support in autorevert.el

[Michael Albinus <michael.albinus@gmx.de>]

Eli Zaretskii <eliz@gnu.org> writes:

> I needed to make 2 changes to get this to work on Windows, see trunk
> revision 111499.  Actually, I don't understand how it worked with
> inotify before my changes, since you were looking for 'modify' in the
> descriptor rather than in the action.  Did I miss something?

You're right, I've introduced a bug here at the very end of my tests
last night.

> Btw, should we perhaps do something more sophisticated than
> string-equal to compare file names?  On Windows, we probably should
> compare case-insensitively, but what about file-truename and friends
> on Posix platforms?

What about `file-equal-p'? Like

--8<---------------cut here---------------start------------->8---
~/src/emacs> bzr diff lisp/autorevert.el
=== modified file 'lisp/autorevert.el'
--- lisp/autorevert.el	2013-01-12 11:25:39 +0000
+++ lisp/autorevert.el	2013-01-12 13:06:19 +0000
@@ -531,17 +531,11 @@
 	(when (featurep 'inotify) (cl-assert (memq 'modify action)))
 	(when (featurep 'w32notify) (cl-assert (eq 'modified action)))
 	(cl-assert (bufferp buffer))
-	(when (stringp file)
-	  (cl-assert (string-equal
-		      ;; w32notify returns the basename of the file
-		      ;; without its leading directories; inotify
-		      ;; returns its full absolute file name.
-                      (file-name-nondirectory (directory-file-name file))
-                      (file-name-nondirectory (directory-file-name
-					       (buffer-file-name buffer))))))
-
-	;; Mark buffer modified.
 	(with-current-buffer buffer
+	  (when (and (stringp file) (stringp buffer-file-name))
+	    (cl-assert (file-equal file buffer-file-name)))
+
+	  ;; Mark buffer modified.
 	  (setq auto-revert-notify-modified-p t))))))
 
 (defun auto-revert-active-p ()
--8<---------------cut here---------------end--------------->8---

The disadvantage might be performance, because `file-equal-p' performs
operations on the filesystem, like `file-attributes' etc. When all files
in a directory are watched, there will be a lot of events to be ignored.
Is this acceptable?

Best regards, Michael.