bug#29111: 26.0.90; Erc keep-place module broken with new default of switch-to-buffer-preserve-window-point

[Jay Kamat]

Hi,

One of the built-in erc modules is keep-place (in erc-goodies), which
keeps the place of point while new messages come into erc. The module
works as expected in Emacs 25.

However, in Emacs 26, enabling this module does nothing in an Emacs -Q
(ie: the point is not saved at all, point is always moved to the bottom
of the buffer).

After much searching, I found this is related to the new default value
(t) of `switch-to-buffer-preserve-window-point'. When setting this
variable back to nil, this issue goes away, and the keep-place module
works as normal on Emacs 26.

Since `switch-to-buffer-preserve-window-point' is defaulting to t, is it
possible to update keep-place to work regardless of this setting? If
that's not a possibility (since this seems to be a global variable),
documentation needs to be updated somehow to make it very clear that
this variable must be set to 'nil' for keep-place to work properly.


I tested this with the minimal init file:

(require 'erc)
(setq erc-modules
          '(autojoin button completion fill irccontrols list match
                                 menu move-to-prompt netsplit networks 
noncommands
                                 readonly ring stamp track truncate keep-place))
(erc-update-modules)


Please let me know if you cannot reproduce.

-Jay

In GNU Emacs 26.0.90 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.22.11)
 of 2017-10-22 built on laythe
Repository revision: 237e96bc5259e59ac5623a93a47f64abffab4e0b
Windowing system distributor 'The X.Org Foundation', version 11.0.11902000
System Description:     Debian GNU/Linux 9.2 (stretch)