bug#10257: 23.3.1 Cygwin: network drives - file is write protected (false positive)

[Ken Brown <kbrown@cornell.edu>]

On 12/13/2011 2:27 PM, Stefan Monnier wrote:
>> I have a question about the emacs side of this.  I wonder what the rationale
>> is for testing writability before trying to save the file, and then asking
>> the user for confirmation in case the (unreliable) test for writability
>> fails (*).
>
> Can you point us to the piece of code about which you're talking?
> Ideally, show us a sample pseudo patch (even better if it compiles, even
> better if it works) showing the kind of change you have in mind.

The code I'm talking about is near the beginning of the definition of 
`basic-save-buffer-2' in files.el:

     (if (not (file-writable-p buffer-file-name))
	(let ((dir (file-name-directory buffer-file-name)))
	  (if (not (file-directory-p dir))
	      (if (file-exists-p dir)
		  (error "%s is not a directory" dir)
		(error "%s: no such directory" dir))
	    (if (not (file-exists-p buffer-file-name))
		(error "Directory %s write-protected" dir)
	      (if (yes-or-no-p
		   (format
		    "File %s is write-protected; try to save anyway? "
		    (file-name-nondirectory
		     buffer-file-name)))
		  (setq tempsetmodes t)
		(error "Attempt to save to a file which you aren't allowed to write"))))))

I'm not (yet) proposing a change.  I'm simply asking what the rationale 
is for calling `yes-or-no-p' and making the user confirm that s/he wants 
to try to save the file.  I don't see that any harm would come from just 
trying to do what the user asked for, without making him/her ask a 
second time.  If the file really is write-protected, there will be an error.

If you agree, then I guess I would propose the following patch (not yet 
tested):

=== modified file 'lisp/files.el'
--- lisp/files.el       2011-12-04 08:02:42 +0000
+++ lisp/files.el       2011-12-13 20:08:55 +0000
@@ -4456,13 +4456,7 @@
                 (error "%s: no such directory" dir))
             (if (not (file-exists-p buffer-file-name))
                 (error "Directory %s write-protected" dir)
-             (if (yes-or-no-p
-                  (format
-                   "File %s is write-protected; try to save anyway? "
-                   (file-name-nondirectory
-                    buffer-file-name)))
-                 (setq tempsetmodes t)
-               (error "Attempt to save to a file which you aren't 
allowed to write"))))))
+             (setq tempsetmodes t)))))
      (or buffer-backed-up
         (setq setmodes (backup-buffer)))
      (let* ((dir (file-name-directory buffer-file-name))


Ken