bug#30639: 25.1; ERC buffer name not unique, broken on reconnect [patch]

bug#30639: 25.1; ERC buffer name not unique, broken on reconnect [patch]

[John Goerzen]

Hi,

Over at https://www.emacswiki.org/emacs/ErcBugs, there is a description
as follows:

"When you're in two channels with the same name, e.g. #hello, on
different networks, the buffers are called #hello and #hello<2>. Now, if
you temporarily lose your connection (e.g. unplug the network cable and
plug it back in) and ERC reconnects, #hello<2> will not be re-used, but
instead #hello<3> will be created."

I have observed this.  This all goes back to a bug in
erc/erc.el:erc-generate-new-buffer-name

The comments in the function as given are reasonable, but the logic
differs.  In particular, the test in the dolist always fails when
(get-buffer candidate) is nil; that is, the test always fails when the
buffer does not already exist.  This causes the test to drop through to
the section at the bottom every time, which results not only in the
server appending logic never being used, but also in the concatenation
of /server never being attempted.

Here is a working replacement:

  (defun erc-generate-new-buffer-name (server port target)
    "Create a new buffer name based on the arguments."
    (when (numberp port) (setq port (number-to-string port)))
    (let ((buf-name (or target
                        (or (let ((name (concat server ":" port)))
                              (when (> (length name) 1)
                                name))
                            ;; This fallback should in fact never happen
                            "*erc-server-buffer*")))
          buffer-name)
      ;; Reuse existing buffers, but not if the buffer is a connected server
      ;; buffer and not if its associated with a different server than the
      ;; current ERC buffer.
      ;; if buf-name is taken by a different connection (or by something !erc)
      ;; then see if "buf-name/server" meets the same criteria
      (dolist (candidate (list buf-name (concat buf-name "/" server)))
        (if (and (not buffer-name)
                 erc-reuse-buffers
                 (or (not (get-buffer candidate))
                     (or target
                         (with-current-buffer (get-buffer candidate)
                           (and (erc-server-buffer-p)
                                (not (erc-server-process-alive)))))
                     (with-current-buffer (get-buffer candidate)
                       (and (string= erc-session-server server)
                            (erc-port-equal erc-session-port port)))))
            (setq buffer-name candidate)))
      ;; if buffer-name is unset, neither candidate worked out for us,
      ;; fallback to the old <N> uniquification method:
      (or buffer-name (generate-new-buffer-name (concat buf-name "/" server))) ))


In GNU Emacs 25.1.1 (x86_64-pc-linux-gnu, GTK+ Version 3.22.11)
 of 2017-09-15, modified by Debian built on trouble
Windowing system distributor 'The X.Org Foundation', version 11.0.11902000
System Description:	Debian GNU/Linux 9.3 (stretch)

Configured using:
 'configure --build x86_64-linux-gnu --prefix=/usr
 --sharedstatedir=/var/lib --libexecdir=/usr/lib
 --localstatedir=/var/lib --infodir=/usr/share/info
 --mandir=/usr/share/man --with-pop=yes
 --enable-locallisppath=/etc/emacs25:/etc/emacs:/usr/local/share/emacs/25.1/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/25.1/site-lisp:/usr/share/emacs/site-lisp
 --with-sound=alsa --build x86_64-linux-gnu --prefix=/usr
 --sharedstatedir=/var/lib --libexecdir=/usr/lib
 --localstatedir=/var/lib --infodir=/usr/share/info
 --mandir=/usr/share/man --with-pop=yes
 --enable-locallisppath=/etc/emacs25:/etc/emacs:/usr/local/share/emacs/25.1/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/25.1/site-lisp:/usr/share/emacs/site-lisp
 --with-sound=alsa --with-x=yes --with-x-toolkit=gtk3
 --with-toolkit-scroll-bars 'CFLAGS=-g -O2
 -fdebug-prefix-map=/build/emacs25-wN2qS3/emacs25-25.1+1=. -fstack-protector-strong
 -Wformat -Werror=format-security -Wall' 'CPPFLAGS=-Wdate-time
 -D_FORTIFY_SOURCE=2' LDFLAGS=-Wl,-z,relro'

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GCONF GSETTINGS
NOTIFY ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11

Important settings:
  value of $LANG: en_US.utf8
  locale-coding-system: utf-8-unix

Major mode: mu4e:main

bug#30639: 25.1; ERC buffer name not unique, broken on reconnect [patch]

[Lars Ingebrigtsen]

John Goerzen <jgoerzen@complete.org> writes:

> The comments in the function as given are reasonable, but the logic
> differs.  In particular, the test in the dolist always fails when
> (get-buffer candidate) is nil; that is, the test always fails when the
> buffer does not already exist.  This causes the test to drop through to
> the section at the bottom every time, which results not only in the
> server appending logic never being used, but also in the concatenation
> of /server never being attempted.
>
> Here is a working replacement:

Thanks; applied to Emacs 27.1.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#30639: 25.1; ERC buffer name not unique, broken on reconnect [patch]

[Kevin Brubeck Unhammer]

Hi,

This commit caused a regression:
https://debbugs.gnu.org/cgi/bugreport.cgi?bug=40121

cdefc045893a7fed57856ac385ab41c71f61c09f makes buffer #hello be used for
*both* networks instead of #hello<2> created on the next network. And
not just that, the other buffers on the same network will get their
network changed (so if #goodbye was on network1, and you connect to
network2 and join #hello there, #goodbye will say it's on network2).

I haven't looked into doing this change correctly yet, but reverting it
at least makes ERC work again for me.


best regards,
Kevin Brubeck Unhammer 

John Goerzen <jgoerzen@complete.org> čálii:

> Hi,
>
> Over at https://www.emacswiki.org/emacs/ErcBugs, there is a description
> as follows:
>
> "When you're in two channels with the same name, e.g. #hello, on
> different networks, the buffers are called #hello and #hello<2>. Now, if
> you temporarily lose your connection (e.g. unplug the network cable and
> plug it back in) and ERC reconnects, #hello<2> will not be re-used, but
> instead #hello<3> will be created."
>
> I have observed this.  This all goes back to a bug in
> erc/erc.el:erc-generate-new-buffer-name
>
> The comments in the function as given are reasonable, but the logic
> differs.  In particular, the test in the dolist always fails when
> (get-buffer candidate) is nil; that is, the test always fails when the
> buffer does not already exist.  This causes the test to drop through to
> the section at the bottom every time, which results not only in the
> server appending logic never being used, but also in the concatenation
> of /server never being attempted.
>
> Here is a working replacement:
>
>   (defun erc-generate-new-buffer-name (server port target)
>     "Create a new buffer name based on the arguments."
>     (when (numberp port) (setq port (number-to-string port)))
>     (let ((buf-name (or target
>                         (or (let ((name (concat server ":" port)))
>                               (when (> (length name) 1)
>                                 name))
>                             ;; This fallback should in fact never happen
>                             "*erc-server-buffer*")))
>           buffer-name)
>       ;; Reuse existing buffers, but not if the buffer is a connected server
>       ;; buffer and not if its associated with a different server than the
>       ;; current ERC buffer.
>       ;; if buf-name is taken by a different connection (or by something !erc)
>       ;; then see if "buf-name/server" meets the same criteria
>       (dolist (candidate (list buf-name (concat buf-name "/" server)))
>         (if (and (not buffer-name)
>                  erc-reuse-buffers
>                  (or (not (get-buffer candidate))
>                      (or target
>                          (with-current-buffer (get-buffer candidate)
>                            (and (erc-server-buffer-p)
>                                 (not (erc-server-process-alive)))))
>                      (with-current-buffer (get-buffer candidate)
>                        (and (string= erc-session-server server)
>                             (erc-port-equal erc-session-port port)))))
>             (setq buffer-name candidate)))
>       ;; if buffer-name is unset, neither candidate worked out for us,
>       ;; fallback to the old <N> uniquification method:
>       (or buffer-name (generate-new-buffer-name (concat buf-name "/" server))) ))
>
>
> In GNU Emacs 25.1.1 (x86_64-pc-linux-gnu, GTK+ Version 3.22.11)
>  of 2017-09-15, modified by Debian built on trouble
> Windowing system distributor 'The X.Org Foundation', version 11.0.11902000
> System Description:	Debian GNU/Linux 9.3 (stretch)
>
> Configured using:
>  'configure --build x86_64-linux-gnu --prefix=/usr
>  --sharedstatedir=/var/lib --libexecdir=/usr/lib
>  --localstatedir=/var/lib --infodir=/usr/share/info
>  --mandir=/usr/share/man --with-pop=yes
>  --enable-locallisppath=/etc/emacs25:/etc/emacs:/usr/local/share/emacs/25.1/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/25.1/site-lisp:/usr/share/emacs/site-lisp
>  --with-sound=alsa --build x86_64-linux-gnu --prefix=/usr
>  --sharedstatedir=/var/lib --libexecdir=/usr/lib
>  --localstatedir=/var/lib --infodir=/usr/share/info
>  --mandir=/usr/share/man --with-pop=yes
>  --enable-locallisppath=/etc/emacs25:/etc/emacs:/usr/local/share/emacs/25.1/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/25.1/site-lisp:/usr/share/emacs/site-lisp
>  --with-sound=alsa --with-x=yes --with-x-toolkit=gtk3
>  --with-toolkit-scroll-bars 'CFLAGS=-g -O2
>  -fdebug-prefix-map=/build/emacs25-wN2qS3/emacs25-25.1+1=. -fstack-protector-strong
>  -Wformat -Werror=format-security -Wall' 'CPPFLAGS=-Wdate-time
>  -D_FORTIFY_SOURCE=2' LDFLAGS=-Wl,-z,relro'
>
> Configured features:
> XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GCONF GSETTINGS
> NOTIFY ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
> TOOLKIT_SCROLL_BARS GTK3 X11
>
> Important settings:
>   value of $LANG: en_US.utf8
>   locale-coding-system: utf-8-unix
>
> Major mode: mu4e:main
>
>
>
>
>