bug#17706: 24.4.50; locked file error in rmail-insert-inbox-text

[Eli Zaretskii <eliz@gnu.org>]

> From: Ken Olum <kdo@cosmos.phy.tufts.edu>
> Cc: 17706@debbugs.gnu.org
> Date: Fri, 06 Jun 2014 12:29:33 -0400
> 
>    From: Eli Zaretskii <eliz@gnu.org>
>    Date: Fri, 06 Jun 2014 18:50:23 +0300
> 
>    I wonder in what Emacs version you don't see it.
> 
> I don't see it in 23.3.  The reason is that this version has a bug in
> which it deletes newlines from the end of the mail file before getting
> new mail.  So it modifies the file before calling
> rmail-insert-inbox-text and so gives the ask-user-about-lock query
> before calling rmail-insert-inbox-text.
> 
> My recollection is that this didn't happen either in builds that I made
> from trunk a few months ago, but I could easily be confused.  In
> particular, I have a bunch of rmail hacks, and if one of these were
> modifying the buffer before rmail-insert-inbox-text it would be the same
> as above.  In 24.3 (using -Q to make sure nothing strange is going on),
> I get the "RMAIL file RMAIL is locked".  So I think we should not worry
> too much about why it seems only to be bothering me now.

Maybe we should improve what Emacs does in this case by calling
ask-user-about-lock instead of just erroring out?  The information
with which to call ask-user-about-lock is already available at that
point, since it is the value returned by file-locked-p.

Then the prompt will be what you expected it to be, and will also be
consistent with what Emacs does when 2 sessions try to modify the same
file.

Would you like to prepare a patch along these lines?