bug#70968: 29.2.50; choose-completion on an emacs22-style completion deletes text after point

[Dmitry Gutov <dmitry@gutov.dev>]

On 07/09/2024 10:30, Eli Zaretskii wrote:
>> Date: Mon, 26 Aug 2024 03:08:56 +0300
>> Cc:sbaugh@janestreet.com,70968@debbugs.gnu.org,juri@linkov.net,
>>   monnier@IRO.UMontreal.CA
>> From: Dmitry Gutov<dmitry@gutov.dev>
>>
>> On 16/05/2024 21:25, Eli Zaretskii wrote:
>>>> I don't think that would be required exactly.
>>>>
>>>> The problem here (IIUC) is that completion behaves differently with the
>>>> emacs22 style depending on whether the execution path went through
>>>> choose-completion (which is not a method of completion style but a
>>>> common subroutine) or not (when completion--do-completion performed
>>>> expansion).
>>> I understand that much.  But what did these two (or their
>>> then-equivalents) do in Emacs 22 and Emacs 23?
>> I'm guessing they behaved incorrectly (or however we want to call the
>> inconsistent behavior), but I don't have a compiled Emacs 22/23 around,
>> and they might be difficult to build.
>>
>> Note that we fixed bug#48356 not too long ago, which is from the same
>> general area, and it probably originated from before Emacs 22/23 too.
>>
>> It's worth looking for edge cases where we'd strongly prefer the current
>> behavior, and they might exist, but so far I only know of situations
>> where the change would be for the better, or the user might be okay with
>> either (example at the end ofhttps://debbugs.gnu.org/72705#35).
> Ping!  How should we proceed with this bug report?

I suggest we come up with a fix (which Stefan might have some ideas 
for), then see which reasonable scenarios get broken, if any. The one 
edge case in Eglot could be fixed in the same Emacs release, I believe.

If any larger scope problems, we could add a variable/option to switch 
to the previous behavior.