bug#66246: ERC buffer is no longer visible

[J.P.]

Hi BTD Master,

Corwin Brust <corwin@bru.st> writes:

> On Wed, Sep 27, 2023 at 3:35 PM BTD Master via Bug reports for GNU
> Emacs, the Swiss army knife of text editors <bug-gnu-emacs@gnu.org>
> wrote:
>>
>> When I login through M-x erc (have also tried erc-tls with the same
>> results), the erc buffer is no longer visible. Emacs instead remains on
>> the previous buffer (in my case *scratch*). This did not happen in
>> previous versions.
>>
>> I'm able to open the buffer when prompted when exiting emacs, but I am
>> not able to use it during the prompt state from C-x C-c.
>>
>> Version: Arch Linux Emacs 29.1-4
>>
>> Thanks.
>
> Hi.  The on-join window handling behaviors saw some changes in 29.1
> (ERC 5.5) and more are in progress for Emacs 30 (ERC 5.6-git on GNU
> ELPA devel).  IIUC, this was motivated because "rolling buffers though
> the active window" was seen as being a potential security hazard.
>
> Please look at ERC NEWS file (M-x erc-news RET) and also the variable
> 'erc-interactive-display' which you almost certainly want to set up in
> your Emacs configuration, going forward.  Once you review those let us
> know if that clears things up or if you suspect there may be a bug
> here.   If you do believe there's a bug it may be helpful to have the
> full output produced by M-x report-emacs-bug  (ideally from a session
> where you've minimally reproduced the problem, so starting from -Q or
> such).

As Corwin helpfully explained, what you're seeing is intentional
(believe it or not) [1]. Just to be clear, you can get the old default
back by doing

  (setopt erc-join-buffer 'buffer)

or

  M-x customize-group RET erc-buffers RET
  C-s erc join buffer RET
  toggling the arrow for item Erc Join Buffer
  and choosing "4 = Use current buffer" from the "Value Menu"
  and then doing C-x C-s or similar to commit the new value

Of course, if you're feeling aggrieved by this development, please make
a case for an alternative [2]. But before that, please consider trying
the new behavior on master [3]. (The option mentioned by Corwin,
`erc-interactive-display', is new in ERC 5.6).

Thanks,
J.P.

P.S. In addition to `report-emacs-bug', you can also try M-x erc-bug
RET, which adds the header "X-Debbugs-CC: emacs-erc@gnu.org" to your
initial email (so we get a copy on ERC's own mailing list) [4].

[1] 
https://git.savannah.gnu.org/cgit/emacs.git/tree/etc/ERC-NEWS?id=d813f71f#n444
    
https://git.savannah.gnu.org/cgit/emacs.git/tree/etc/ERC-NEWS?id=d813f71f#n48
[2] https://lists.gnu.org/archive/html/emacs-erc/2023-06/msg00006.html
[3] https://emacs-erc.gitlab.io/bugs/archive/doc/erc.html#Upgrading
[4] https://lists.gnu.org/mailman/listinfo/emacs-erc