bug#56449: 29.0.50; Revisit target shortcuts in erc-message

[J.P.]

Tags: patch

The purpose of the function `erc-message' is to provide a "target
shortcut" option to a handful of "slash" commands, mostly ones emitting
a PRIVMSG. When a user invoking such a command supplies a period or a
comma instead of a channel or a nick, whatever's stored in the relevant
slot of `erc-server-last-peers' gets substituted in the outgoing
message. IOW, issuing a

  ERC> /MSG , hi

recalls the last nick to speak over a given connection. And

  ERC> /MSG . hi

reuses the target (channel or query) from the last `erc-message'
invocation, which may have been something like

  ERC> /MSG bob hi

with no actual shortcut present. As it happens, these targets are
stashed in the default value shared across all connections, which is
almost certainly undesirable. But attempting to fix it forces us to
confront some basic usability concerns that vary based on whatever we
deem to be the feature's intended "scope":

1. Network (patch)

   The name of the variable in question, `erc-server-last-peers', may
   suggest that this feature should be scoped per IRC connection. But
   what's the point of blindly addressing the last speaker among all of
   a network's buffers without knowing exactly who you're engaging?

2. Buffer-local

   Using a "," for PM'ing the last speaker in a target buffer may lead
   to a surprise if anyone else speaks before you've submitted the
   input. As with (1), only the logs know for sure. Also, the "." form
   is only useful so long as you refrain from speaking.

For now, I propose temporarily adopting (1) by confining shared values
to server buffers. As far as attempting to renovate this feature goes
(rather than, say, tacitly retiring it), I think it's worth considering
that nick completion and abbrevs have long provided capable
alternatives.

In that vein, the last patch below claims to offer a compromise that
somewhat extends the existing pcomplete integration for the affected
slash commands so that dots and commas expand to their relevant targets
in the input area. This reduces potential targeting errors by offering
visual confirmation. IOW, if the last person to speak was Alice, typing

  ERC> /m ,[TAB]

would expand to

  ERC> /m alice _

And while this demo is built atop (1), the idea could easily be adapted
for (2) or another variant. BTW, if anyone has experience with
pcomplete, I'm pretty sure I committed an epic faceplant in trying to
apply the API. If we end up going with this, please help. But, for now,
the door remains wide open, and alternative solutions are more than
welcome.

Thanks,
J.P.

P.S. This bug isn't (yet) claimed by any particular ERC release.


In GNU Emacs 29.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.34, cairo 
version 1.17.6)
 of 2022-07-06 built on localhost
Repository revision: e6504c3eda12c72268d2db6598764f043b74c24d
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0001-Demo-mutating-default-value-of-erc-server-last-peers.patch
Description: Text Data

0002-SQUASH-Avoid-mutating-default-value-of-erc-server-la.patch
Description: Text Data

0003-POC-FIXME-Add-erc-message-shortcuts-to-erc-pcomplete.patch
Description: Text Data