Tags: patch

In the early days of IRC, parsing a "MODE" command from the server was
comparatively straightforward. There were a few well known letters, some
taking a single argument, and a standard set of status prefixes. But
somewhere along the line, things got more complicated, and it seems ERC
never got the memo. While it may appear obvious that sticking to a
hard-coded, heuristics based approach doesn't really accommodate ERC's
core tenet of extensibility, the risk of shifting toward something more
parameter driven was probably never justifiable without a vocal demand.
Or an obvious bug.

From emacs -Q:

  1. Connect to Libera.Chat
  2. Create ##mychan
  3. /mode ##mychan +Qu

  debugger entered--Lisp error: (wrong-type-argument char-or-string-p nil)
    erc-downcase(nil)
    erc-update-current-channel-member(nil nil nil nil nil nil nil on ...)
    erc-update-channel-member("#libera" nil nil nil nil nil nil nil on)
    erc-update-modes("##mychan" "+Qu" "mynick" "user/foo" "Hi!")

The issue here is that ERC doesn't account for ISUPPORT parameters when
parsing MODE commands and dispatching handlers. Instead, it simply
assumes that +q (or +Q) means someone has just been promoted to a
channel owner.

I'll admit that although I've been aware of this basic issue for quite
some time, I've been hesitant to cross this bridge until 5.7+ because of
the potential pitfalls involved. In any case, with a concrete bug having
surfaced (courtesy of Corwin), the issue has been forced, and it's one
that can't really be papered over responsibly just to avoid holding up
the current release. My proposed means of addressing this is mainly
contained in the last of the attached patches. The approach comes down
to rewriting the most important bits and providing adapters to reroute
the rest accordingly. Comments welcome, as always. Thanks.


In GNU Emacs 30.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version
 3.24.38, cairo version 1.17.6) of 2023-11-15 built on localhost
Repository revision: ff1f82cbe3fa9aee354581f2798faaae7163ea44
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12014000
System Description: Fedora Linux 37 (Workstation Edition)

Configured using:
 'configure --enable-check-lisp-object-type --enable-checking=yes,glyphs
 'CFLAGS=-O0 -g3'
 PKG_CONFIG_PATH=:/usr/lib64/pkgconfig:/usr/share/pkgconfig'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG
JSON LCMS2 LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 M17N_FLT MODULES NOTIFY
INOTIFY PDUMPER PNG RSVG SECCOMP SOUND SQLITE3 THREADS TIFF
TOOLKIT_SCROLL_BARS WEBP X11 XDBE XIM XINPUT2 XPM GTK3 ZLIB

Important settings:
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  minibuffer-regexp-mode: t
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message mailcap yank-media puny dired
dired-loaddefs rfc822 mml mml-sec epa epg rfc6068 epg-config gnus-util
text-property-search time-date mm-decode mm-bodies mm-encode mail-parse
rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045
ietf-drums mm-util mail-prsvr mail-utils erc derived auth-source eieio
eieio-core password-cache json map format-spec erc-backend erc-networks
easy-mmode byte-opt bytecomp byte-compile erc-common inline erc-compat
cl-seq cl-macs gv pcase rx subr-x cl-loaddefs cl-lib erc-loaddefs rmc
iso-transl tooltip cconv eldoc paren electric uniquify ediff-hook
vc-hooks lisp-float-type elisp-mode mwheel term/x-win x-win
term/common-win x-dnd touch-screen tool-bar dnd fontset image regexp-opt
fringe tabulated-list replace newcomment text-mode lisp-mode prog-mode
register page tab-bar menu-bar rfn-eshadow isearch easymenu timer select
scroll-bar mouse jit-lock font-lock syntax font-core term/tty-colors
frame minibuffer nadvice seq simple cl-generic indonesian philippine
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code-pages mule custom widget keymap hashtable-print-readable backquote
threads dbusbind inotify lcms2 dynamic-setting system-font-setting
font-render-setting cairo gtk x-toolkit xinput2 x multi-tty move-toolbar
make-network-process emacs)

Memory information:
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