bug#36843: 26.2; ERC lurker feature broken

[Amin Bandali]

Below is a patch that seems to fix this.  I haven’t tested the actual
patch but I’ve added its changed to my init file (adding the new defvar,
and redefining erc-display-message and erc-lurker-update-status) for the
last couple of days, and it seems to work as intended.

Thanks to Noam for helping me with this over on #emacs.

>From 389654f5c7a9ad0975bff84a163ed6234cdb3cb8 Mon Sep 17 00:00:00 2001
From: Amin Bandali <bandali@gnu.org>
Date: Sat, 17 Aug 2019 14:09:11 -0400
Subject: [PATCH] Fix erc-lurker-update-status

Fix erc-lurker-update-status (bug#36843), broken since
d0fcaff514d2be16ccf73817f658318cf85221e3.

* lisp/erc/erc.el: define `erc-message-parsed', lexically bind it in
  `erc-display-message', and change `erc-lurker-update-status' to use
  that instead of using `parsed' directly.  This results in
  `erc-lurker-state' being properly updated to keep track of
  non-lurkers, and thus `erc-lurker-p' returning correct results
  rather than return t for everyone.
---
 lisp/erc/erc.el | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/lisp/erc/erc.el b/lisp/erc/erc.el
index f5c9decc3a..9ea9e608ac 100644
--- a/lisp/erc/erc.el
+++ b/lisp/erc/erc.el
@@ -2594,6 +2594,8 @@ erc-lurker-cleanup-interval
 consumption of lurker state during long Emacs sessions and/or ERC
 sessions with large numbers of incoming PRIVMSGs.")
 
+(defvar erc-message-parsed)
+
 (defun erc-lurker-update-status (_message)
   "Update `erc-lurker-state' if necessary.
 
@@ -2603,18 +2605,20 @@ erc-lurker-update-status
 current time.  Otherwise, take no action.
 
 This function depends on the fact that `erc-display-message'
-dynamically binds `parsed', which is used to check if the current
-message is a PRIVMSG and to determine its sender.  See also
-`erc-lurker-trim-nicks' and `erc-lurker-ignore-chars'.
+dynamically binds `erc-message-parsed', which is used to check if
+the current message is a PRIVMSG and to determine its sender.
+See also `erc-lurker-trim-nicks' and `erc-lurker-ignore-chars'.
 
 In order to limit memory consumption, this function also calls
 `erc-lurker-cleanup' once every `erc-lurker-cleanup-interval'
 updates of `erc-lurker-state'."
-  (when (and (boundp 'parsed) (erc-response-p parsed))
-    (let* ((command (erc-response.command parsed))
+  (when (and (boundp 'erc-message-parsed)
+            (erc-response-p erc-message-parsed))
+    (let* ((command (erc-response.command erc-message-parsed))
            (sender
             (erc-lurker-maybe-trim
-             (car (erc-parse-user (erc-response.sender parsed)))))
+             (car (erc-parse-user
+                  (erc-response.sender erc-message-parsed)))))
            (server
             (erc-canonicalize-server-name erc-server-announced-name)))
       (when (equal command "PRIVMSG")
@@ -2704,7 +2708,8 @@ erc-display-message
 See also `erc-format-message' and `erc-display-line'."
   (let ((string (if (symbolp msg)
                     (apply #'erc-format-message msg args)
-                  msg)))
+                  msg))
+       (erc-message-parsed parsed))
     (setq string
           (cond
            ((null type)
-- 
2.22.0