[erc] buffer-file-truename vs. erc [was vs. info.el]

[stephen at xemacs.org]

[Adrian, since this affects ERC, too, would you please take a look at
this patch?  It's correct in theory, but I don't know anything about
ERC.]

Nelson Ferreira writes:

 > I am sorry, but should there have been a patch attached?

Yes; you should have received the resend by now.  Very sorry about that!

 > This has also happened to me in some ERC buffers, specially the ones
 > where part of the history from logs were pulled out from the disk. I
 > will try to remember if there were any more cases. Those 2 are
 > certainly the ones I encounter repeatedly.

Thanks!  I've taken a look at ERC.  I have no idea what they think
they're doing here in erc-log.el:

;;;functionality referenced from erc.el
(defun erc-log-setup-logging ()
  "Setup the buffer-local logging variables in the current buffer.
This function is destined to be run from `erc-connect-pre-hook'."
  (when (erc-logging-enabled)
    (auto-save-mode -1)
    (setq buffer-offer-save t
	  buffer-file-name "")
    ;; code continues ...

The empty string looks very suspicious, I can't see how anything good
might come of it.  I propose changing it to nil and setq'ing
buffer-file-truename to nil, too, to maintain the invariant.  If that
doesn't work, you might need to change it to something like

    (setq buffer-offer-save t
	  buffer-file-name (erc-current-logfile buffer)
          buffer-file-truename (file-truename buffer-file-name))

or you could try

    (setq buffer-offer-save t
	  buffer-file-name ""
          buffer-file-truename (file-truename buffer-file-name))

but it all seems very hackish.

Index: ChangeLog
===================================================================
RCS file: /pack/xemacscvs/XEmacs/packages/xemacs-packages/erc/ChangeLog,v
retrieving revision 1.40
diff -U0 -r1.40 ChangeLog
--- ChangeLog	2 May 2006 06:38:43 -0000	1.40
+++ ChangeLog	14 Nov 2006 09:02:44 -0000
@@ -0,0 +1,5 @@
+2006-11-14  Stephen J. Turnbull  <stephen at xemacs.org>
+
+	* erc-dcc.el (erc-dcc-find-file,erc-log-setup-logging):
+	Maintain buffer-file-name invariant.
+

Index: erc-dcc.el
===================================================================
RCS file: /pack/xemacscvs/XEmacs/packages/xemacs-packages/erc/erc-dcc.el,v
retrieving revision 1.9
diff -u -r1.9 erc-dcc.el
--- erc-dcc.el	19 Feb 2006 12:57:28 -0000	1.9
+++ erc-dcc.el	14 Nov 2006 09:02:50 -0000
@@ -776,7 +776,9 @@
 (defun erc-dcc-find-file (file)
   (with-current-buffer (generate-new-buffer (file-name-nondirectory file))
     (insert-file-contents-literally file)
-    (setq buffer-file-name file)
+    ;; XEmacs change: maintain invariant for truename vs. name.
+    (setq buffer-file-name file
+          buffer-file-truename (file-truename buffer-file-name))
     (current-buffer)))
 
 (defun erc-dcc-file-to-name (file)
Index: erc-log.el
===================================================================
RCS file: /pack/xemacscvs/XEmacs/packages/xemacs-packages/erc/erc-log.el,v
retrieving revision 1.9
diff -u -r1.9 erc-log.el
--- erc-log.el	19 Feb 2006 12:57:29 -0000	1.9
+++ erc-log.el	14 Nov 2006 09:02:51 -0000
@@ -219,7 +219,8 @@
   (when (erc-logging-enabled)
     (auto-save-mode -1)
     (setq buffer-offer-save t
-	  buffer-file-name "")
+	  buffer-file-name nil
+	  buffer-file-truename nil)
     (cond ((boundp 'write-file-functions)
 	   (set (make-local-variable 'write-file-functions)
 		'(erc-save-buffer-in-logs)))