Re: bug#67032: 30.0.50; ERC 5.6-git: Treat erc-send-message more responsibly

From 96b62219e43df0585ddfbabaa904342ca0385d22 Mon Sep 17 00:00:00 2001
From: "F. Jason Park" <[email protected]>
Date: Fri, 10 Nov 2023 16:28:33 -0800
Subject: [PATCH 0/6] *** NOT A PATCH ***

*** BLURB HERE ***

F. Jason Park (6):
  [5.6] Make ERC error-notice formatting more consistent
  [5.6] Make ERC's message-sending functions more flexible
  [5.6] Simplify logic for inserting ERC prompt input
  [5.6] Slightly simplify text props on echoed ERC input
  [5.6] Don't output non-modules in erc-modes
  [5.6] Revive erc-display-command as module command-indicator

 etc/ERC-NEWS               |  15 ++++
 lisp/erc/erc-backend.el    |  16 ++--
 lisp/erc/erc-goodies.el    | 113 +++++++++++++++++++++--
 lisp/erc/erc-match.el      |  14 +--
 lisp/erc/erc.el            | 177 +++++++++++++++++++++----------------
 test/lisp/erc/erc-tests.el |   5 +-
 6 files changed, 238 insertions(+), 102 deletions(-)

Interdiff:
diff --git a/etc/ERC-NEWS b/etc/ERC-NEWS
index f59023eae62..49b623aa7f0 100644
--- a/etc/ERC-NEWS
+++ b/etc/ERC-NEWS
@@ -157,6 +157,21 @@ asking users who've customized this option to switch to
 that some other solution, like automatic migration, is justified,
 please make that known on the bug list.
 
+** Module 'noncommands' deprecated, replaced by 'command-indicator'.
+Command-line echoing has returned to ERC after a near-decade-long
+hiatus.  This means you can elect to have ERC leave a trail of most
+slash-command input submitted at the prompt, in a manner resembling a
+shell or a REPL.  The particulars are likely of little interest to
+most users, but the gist is that this functionality was removed in
+5.3.x (Emacs 24.5) under mysterious circumstances, without mention in
+this document or any change log.  Everything's mostly been restored,
+except that the feature is now opt-in.  (Add 'command-indicator' to
+'erc-modules' to get started.)  The only real gotcha is that related
+faces and options, like 'erc-command-indicator', have moved to the
+'erc-goodies' library, although their Custom groups remain the same.
+Hint: once enabled, use 'erc-command-indicator-toggle-hidden' to
+dynamically toggle echoed command-line visibility.
+
 ** 'erc-button-alist' and 'erc-nick-popup-alist' have evolved slightly.
 It's no secret that the 'buttons' module treats potential nicknames
 specially.  This is perhaps most evident in its treatment of the
diff --git a/lisp/erc/erc-goodies.el b/lisp/erc/erc-goodies.el
index 4cc81dd9378..93b76c544aa 100644
--- a/lisp/erc/erc-goodies.el
+++ b/lisp/erc/erc-goodies.el
@@ -471,21 +471,26 @@ erc-noncommands-list
                                erc-cmd-COUNTRY
                                erc-cmd-SV
                                erc-cmd-SM
-                               erc-cmd-SMV
+                               erc-cmd-SAY
                                erc-cmd-LASTLOG)
-  "List of commands that are aliases for CTCP ACTION or for ERC messages.
-
-If a command's function symbol is in this list, the typed command
-does not appear in the ERC buffer after the user presses ENTER.")
+  "List of commands that perform their own buffer I/O.
+The `command-indicator' module forgoes echoing commands in this
+list.")
 
 ;;;###autoload(autoload 'erc-noncommands-mode "erc-goodies" nil t)
 (define-erc-module noncommands nil
-  "This mode distinguishes non-commands.
-Commands listed in `erc-insert-this' know how to display
-themselves."
+  "Treat commands that display themselves specially.
+This module has been a no-op since ERC 5.3 and has likely only
+ever made sense in the context of `erc-command-indicator'.  It
+was deprecated in ERC 5.6."
   ((add-hook 'erc--input-review-functions #'erc-send-distinguish-noncommands))
   ((remove-hook 'erc--input-review-functions
                 #'erc-send-distinguish-noncommands)))
+(make-obsolete-variable 'erc-noncommand-mode
+                        'erc-command-indicator-mode "30.1")
+(make-obsolete 'erc-noncommand-mode 'erc-command-indicator-mode "30.1")
+(make-obsolete 'erc-noncommand-enable 'erc-command-indicator-enable "30.1")
+(make-obsolete 'erc-noncommand-disable 'erc-command-indicator-disable "30.1")
 
 (defun erc-send-distinguish-noncommands (state)
   "If STR is an ERC non-command, set `insertp' in STATE to nil."
@@ -499,6 +504,98 @@ erc-send-distinguish-noncommands
       ;; Inhibit sending this string.
       (setf (erc-input-insertp state) nil))))
 
+
+;;; Command-indicator
+
+(defface erc-command-indicator-face
+  '((t :inherit (shadow fixed-pitch-serif)))
+  "Face for echoed command lines, including the prompt.
+See option `erc-command-indicator'."
+  :package-version '(ERC . "5.6")
+  :group 'erc-faces)
+
+(defcustom erc-command-indicator "$>"
+  "Pseudo prompt for echoed command lines.
+An analog of the option `erc-prompt' that replaces the \"speaker
+label\" for echoed \"slash\" commands submitted at the prompt.  A
+value of nil means ERC only inserts the command line portion,
+sans pseudo prompt, which may trick certain modules into treating
+the slash command itself as the message's \"speaker\"."
+  :package-version '(ERC . "5.6")
+  :group 'erc-display
+  :type '(choice (const "$>") (const nil) string function))
+
+;;;###autoload(autoload 'erc-command-indicator-mode "erc-goodies" nil t)
+(define-erc-module command-indicator nil
+  "Echo command lines for \"slash commands,\" like /JOIN, /HELP, etc.
+Skip those appearing in `erc-noncommands-list'.
+
+Users can run \\[erc-command-indicator-toggle-hidden] to hide and
+reveal echoed command lines after they've been inserted."
+  ((add-hook 'erc--input-review-functions
+             #'erc--command-indicator-permit-insertion 90 t)
+   (erc-command-indicator-toggle-hidden -1))
+  ((remove-hook 'erc--input-review-functions
+                #'erc--command-indicator-permit-insertion t)
+   (erc-command-indicator-toggle-hidden +1))
+  'local)
+
+(defun erc-command-indicator ()
+  "Return the command-indicator prompt as a string.
+Do nothing if the variable `erc-command-indicator' is nil."
+  (and erc-command-indicator
+       (let ((prompt (if (functionp erc-command-indicator)
+                         (funcall erc-command-indicator)
+                       erc-command-indicator)))
+         (concat prompt (and (not (string-empty-p prompt)) " ")))))
+
+(defun erc-command-indicator-toggle-hidden (arg)
+  "Toggle whether echoed \"slash commands\" are visible."
+  (interactive "P")
+  (erc--toggle-hidden 'command-indicator arg))
+
+(defun erc--command-indicator-permit-insertion (state)
+  "Insert `erc-input' STATE's message if it's an echoed command."
+  (cl-assert erc-command-indicator-mode)
+  (when (erc--input-split-cmdp state)
+    (setf (erc--input-split-insertp state) #'erc--command-indicator-display)
+    (erc-send-distinguish-noncommands state)))
+
+;; That function used to be called `erc-display-command'.  It was
+;; neutered in ERC 5.3.x (Emacs 24.5), commented out in 5.4, removed
+;; in 5.5, and restored in 5.6.
+(defun erc--command-indicator-display (line)
+  "Insert command LINE as echoed input resembling that of REPLs and shells."
+  (when erc-insert-this
+    (save-excursion
+      (erc--assert-input-bounds)
+      (let ((insert-position (marker-position (goto-char erc-insert-marker)))
+            (erc--msg-props (or erc--msg-props
+                                (let ((ovs erc--msg-prop-overrides))
+                                  (map-into `((erc-msg . slash-cmd)
+                                              ,@(reverse ovs))
+                                            'hash-table)))))
+        (when-let ((string (erc-command-indicator))
+                   (erc-input-marker (copy-marker erc-input-marker)))
+          (erc-display-prompt nil nil string 'erc-command-indicator-face)
+          (set-marker erc-input-marker nil))
+        (let ((beg (point)))
+          (insert line)
+          (erc-put-text-property beg (point)
+                                 'font-lock-face 'erc-command-indicator-face)
+          (insert "\n"))
+        (save-restriction
+          (narrow-to-region insert-position (point))
+          (run-hooks 'erc-send-modify-hook)
+          (run-hooks 'erc-send-post-hook)
+          (cl-assert (> (- (point-max) (point-min)) 1))
+          (erc--hide-message 'command-indicator)
+          (add-text-properties (point-min) (1+ (point-min))
+                               (erc--order-text-properties-from-hash
+                                erc--msg-props))))
+      (erc--refresh-prompt))))
+
+
 ;;; IRC control character processing.
 (defgroup erc-control-characters nil
   "Dealing with control characters."
diff --git a/lisp/erc/erc-match.el b/lisp/erc/erc-match.el
index 8644e61106f..6fff54d3cf4 100644
--- a/lisp/erc/erc-match.el
+++ b/lisp/erc/erc-match.el
@@ -695,19 +695,7 @@ erc-match-toggle-hidden-fools
 Expect the function `erc-hide-fools' or similar to be present in
 `erc-text-matched-hook'."
   (interactive "P")
-  (erc-match--toggle-hidden 'match-fools arg))
-
-(defun erc-match--toggle-hidden (prop arg)
-  "Toggle invisibility for spec member PROP.
-Treat ARG in a manner similar to mode toggles defined by
-`define-minor-mode'."
-  (when arg
-    (setq arg (prefix-numeric-value arg)))
-  (if (memq prop (ensure-list buffer-invisibility-spec))
-      (unless (natnump arg)
-        (remove-from-invisibility-spec prop))
-    (when (or (not arg) (natnump arg))
-      (add-to-invisibility-spec prop))))
+  (erc--toggle-hidden 'match-fools arg))
 
 (provide 'erc-match)
 
diff --git a/lisp/erc/erc.el b/lisp/erc/erc.el
index 00ee97b7e14..89b3397d8f1 100644
--- a/lisp/erc/erc.el
+++ b/lisp/erc/erc.el
@@ -346,8 +346,13 @@ erc-hide-prompt
   "If non-nil, hide input prompt upon disconnecting.
 To unhide, type something in the input area.  Once revealed, a
 prompt remains unhidden until the next disconnection.  Channel
-prompts are unhidden upon rejoining.  See
-`erc-unhide-query-prompt' for behavior concerning query prompts."
+prompts are unhidden upon rejoining.  For behavior concerning
+query prompts, see `erc-unhide-query-prompt'.  Longtime ERC users
+should note that this option was repurposed in ERC 5.5 because it
+had lain dormant for years after being sidelined in 5.3 when its
+only use in the interactive client was removed.  Before then, its
+role was controlling whether `erc-command-indicator' would appear
+alongside echoed slash-command lines."
   :package-version '(ERC . "5.5")
   :group 'erc-display
   :type '(choice (const :tag "Always hide prompt" t)
@@ -759,28 +764,6 @@ erc-prompt
         (concat prompt " ")
       prompt)))
 
-(defcustom erc-command-indicator nil
-  "Indicator used by ERC for showing commands.
-
-If non-nil, this will be used in the ERC buffer to indicate
-commands (i.e., input starting with a `/').
-
-If nil, the prompt will be constructed from the variable `erc-prompt'."
-  :group 'erc-display
-  :type '(choice (const nil) string function))
-
-(defun erc-command-indicator ()
-  "Return the command indicator prompt as a string.
-
-This only has any meaning if the variable `erc-command-indicator' is non-nil."
-  (and erc-command-indicator
-       (let ((prompt (if (functionp erc-command-indicator)
-                         (funcall erc-command-indicator)
-                       erc-command-indicator)))
-         (if (> (length prompt) 0)
-             (concat prompt " ")
-           prompt))))
-
 (defcustom erc-notice-prefix "*** "
   "Prefix for all notices."
   :group 'erc-display
@@ -1364,12 +1347,6 @@ erc-prompt-face
   "ERC face for the prompt."
   :group 'erc-faces)
 
-(defface erc-command-indicator-face
-  '((t :weight bold))
-  "ERC face for the command indicator.
-See the variable `erc-command-indicator'."
-  :group 'erc-faces)
-
 (defface erc-notice-face
   '((default :weight bold)
     (((class color) (min-colors 88) (supports :weight semi-bold))
@@ -2077,7 +2054,7 @@ erc--sort-modules
 
 (defcustom erc-modules '( autojoin button completion fill imenu irccontrols
                           list match menu move-to-prompt netsplit
-                          networks noncommands readonly ring stamp track)
+                          networks readonly ring stamp track)
   "A list of modules which ERC should enable.
 If you set the value of this without using `customize' remember to call
 \(erc-update-modules) after you change it.  When using `customize', modules
@@ -2127,6 +2104,7 @@ erc-modules
     (const :tag "button: Buttonize URLs, nicknames, and other text" button)
     (const :tag "capab: Mark unidentified users on servers supporting CAPAB"
            capab-identify)
+    (const :tag "command-indicator: Echo command lines." command-indicator)
     (const :tag "completion: Complete nicknames and commands (programmable)"
            completion)
     (const :tag "dcc: Provide Direct Client-to-Client support" dcc)
@@ -2146,7 +2124,7 @@ erc-modules
     (const :tag "networks: Provide data about IRC networks" networks)
     (const :tag "nickbar: Show nicknames in a dyamic side window" nickbar)
     (const :tag "nicks: Uniquely colorize nicknames in target buffers" nicks)
-    (const :tag "noncommands: Don't display non-IRC commands after evaluation"
+    (const :tag "noncommands: Deprecated. See module `command-indicator'."
            noncommands)
     (const :tag "notifications: Desktop alerts on PRIVMSG or mentions"
            notifications)
@@ -3309,6 +3287,18 @@ erc--hide-message
           (cl-incf beg))
         (erc--merge-prop (1- beg) (1- end) 'invisible value)))))
 
+(defun erc--toggle-hidden (prop arg)
+  "Toggle invisibility for spec member PROP.
+Treat ARG in a manner similar to mode toggles defined by
+`define-minor-mode'."
+  (when arg
+    (setq arg (prefix-numeric-value arg)))
+  (if (memq prop (ensure-list buffer-invisibility-spec))
+      (unless (natnump arg)
+        (remove-from-invisibility-spec prop))
+    (when (or (not arg) (natnump arg))
+      (add-to-invisibility-spec prop))))
+
 (defun erc--delete-inserted-message (beg-or-point &optional end)
   "Remove message between BEG and END.
 Expect BEG and END to match bounds as returned by the macro
@@ -7016,7 +7006,9 @@ erc--send-input-lines
   (when (erc--input-split-sendp lines-obj)
     (dolist (line (erc--input-split-lines lines-obj))
       (when (erc--input-split-insertp lines-obj)
-        (erc-display-msg line))
+        (if (functionp (erc--input-split-insertp lines-obj))
+            (funcall (erc--input-split-insertp lines-obj) line)
+          (erc-display-msg line)))
       (erc-process-input-line (concat line "\n")
                               (null erc-flood-protect)
                               (not (erc--input-split-cmdp lines-obj))))))
@@ -7522,7 +7514,10 @@ erc-load-irc-script-lines
 user input."
   (let* ((cb (current-buffer))
          (s "")
-         (sp (or (erc-command-indicator) (erc-prompt)))
+         (sp (or (and (bound-and-true-p erc-command-indicator-mode)
+                      (fboundp 'erc-command-indicator)
+                      (erc-command-indicator))
+                 (erc-prompt)))
          (args (and (boundp 'erc-script-args) erc-script-args)))
     (if (and args (string-match "^ " args))
         (setq args (substring args 1)))
diff --git a/test/lisp/erc/erc-tests.el b/test/lisp/erc/erc-tests.el
index 2898ca7be75..e7422d330c0 100644
--- a/test/lisp/erc/erc-tests.el
+++ b/test/lisp/erc/erc-tests.el
@@ -2543,7 +2543,8 @@ erc-handle-irc-url
     (kill-buffer "#chan")))
 
 (defconst erc-tests--modules
-  '( autoaway autojoin bufbar button capab-identify completion dcc fill identd
+  '( autoaway autojoin bufbar button capab-identify
+     command-indicator completion dcc fill identd
      imenu irccontrols keep-place list log match menu move-to-prompt netsplit
      networks nickbar nicks noncommands notifications notify page readonly
      replace ring sasl scrolltobottom services smiley sound
-- 
2.41.0

From 7e3b7c789f0c8b8d658b2571d09b124edc94edbd Mon Sep 17 00:00:00 2001
From: "F. Jason Park" <[email protected]>
Date: Wed, 8 Nov 2023 19:14:55 -0800
Subject: [PATCH 1/6] [5.6] Make ERC error-notice formatting more consistent

* lisp/erc/erc-backend.el (erc--server-propagate-failed-connection):
Print leading notice prefix when reporting process exit status, and
set `erc-msg' type to `notice-error'.
(erc-schedule-reconnect): Print leading notice prefix when printing
`reconnecting' message.
* lisp/erc/erc.el (erc-process-input-line, erc-cmd-PART,
erc-cmd-TOPIC): Print `no-target' messages as error notices.
(erc-message-english-disconnected,
erc-message-english-disconnected-noreconnect): Hard-code standard
"***" notice prefix into message text, for consistency.
* test/lisp/erc/erc-tests.el (erc--refresh-prompt): Expect notice
prefix before `no-target' message.
---
 lisp/erc/erc-backend.el    |  4 ++--
 lisp/erc/erc.el            | 11 ++++++-----
 test/lisp/erc/erc-tests.el |  2 +-
 3 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/lisp/erc/erc-backend.el b/lisp/erc/erc-backend.el
index 4b5edaa77d2..32d891cd1c6 100644
--- a/lisp/erc/erc-backend.el
+++ b/lisp/erc/erc-backend.el
@@ -728,7 +728,7 @@ erc--server-propagate-failed-connection
 the server buffer in any case."
   (when (eq (process-status process) 'failed)
     (erc-display-message
-     nil 'error (process-buffer process)
+     nil '(notice error) (process-buffer process)
      (format "Process exit status: %S" (process-exit-status process)))
     (pcase (process-exit-status process)
       (111
@@ -995,7 +995,7 @@ erc-schedule-reconnect
                     (- erc-server-reconnect-attempts
                        (cl-incf erc-server-reconnect-count (or incr 1)))))
         (proc (buffer-local-value 'erc-server-process buffer)))
-    (erc-display-message nil 'error buffer 'reconnecting
+    (erc-display-message nil '(notice error) buffer 'reconnecting
                          ?m erc-server-reconnect-timeout
                          ?i (if count erc-server-reconnect-count "N")
                          ?n (if count erc-server-reconnect-attempts "A"))
diff --git a/lisp/erc/erc.el b/lisp/erc/erc.el
index fd57cb9d6a0..2d8f388328d 100644
--- a/lisp/erc/erc.el
+++ b/lisp/erc/erc.el
@@ -3729,7 +3729,7 @@ erc-process-input-line
       (let ((r (erc-default-target)))
         (if r
             (funcall erc-send-input-line-function r line force)
-          (erc-display-message nil 'error (current-buffer) 'no-target)
+          (erc-display-message nil '(notice error) (current-buffer) 'no-target)
           nil)))))
 
 (defconst erc--shell-parse-regexp
@@ -4581,7 +4581,7 @@ erc-cmd-PART
                                  (format "PART %s" ch)
                                (format "PART %s :%s" ch reason))
                              nil ch))
-        (erc-display-message nil 'error (current-buffer) 'no-target)))
+        (erc-display-message nil '(notice error) (current-buffer) 'no-target)))
     t)
    (t nil)))
 (put 'erc-cmd-PART 'do-not-parse-args t)
@@ -4921,7 +4921,7 @@ erc-cmd-TOPIC
           (progn
             (erc-log (format "cmd: TOPIC [%s]: %s" ch topic))
             (erc-server-send (format "TOPIC %s :%s" ch topic) nil ch))
-        (erc-display-message nil 'error (current-buffer) 'no-target)))
+        (erc-display-message nil '(notice error) (current-buffer) 'no-target)))
     t)
    (t nil)))
 (defalias 'erc-cmd-T #'erc-cmd-TOPIC)
@@ -8194,9 +8194,10 @@ erc-define-catalog
    (flood-ctcp-off . "FLOOD PROTECTION: Automatic CTCP responses turned off.")
    (flood-strict-mode
     . "FLOOD PROTECTION: Switched to Strict Flood Control mode.")
-   (disconnected . "\n\nConnection failed!  Re-establishing connection...\n")
+   (disconnected
+    . "\n\n*** Connection failed!  Re-establishing connection...\n")
    (disconnected-noreconnect
-    . "\n\nConnection failed!  Not re-establishing connection.\n")
+    . "\n\n*** Connection failed!  Not re-establishing connection.\n")
    (reconnecting . "Reconnecting in %ms: attempt %i/%n ...")
    (reconnect-canceled . "Canceled %u reconnect timer with %cs to go...")
    (finished . "\n\n*** ERC finished ***\n")
diff --git a/test/lisp/erc/erc-tests.el b/test/lisp/erc/erc-tests.el
index 916b394c8ff..2898ca7be75 100644
--- a/test/lisp/erc/erc-tests.el
+++ b/test/lisp/erc/erc-tests.el
@@ -317,7 +317,7 @@ erc--refresh-prompt
         (insert "Howdy")
         (erc-send-current-line)
         (save-excursion (forward-line -1)
-                        (should (looking-at "No target"))
+                        (should (looking-at (rx "*** No target")))
                         (forward-line -1)
                         (should (looking-at "<tester> Howdy")))
         (should (looking-back "ServNet 6> "))
-- 
2.41.0

From a3bd16a010472ca6b4ce54cb5230f246e84c685d Mon Sep 17 00:00:00 2001
From: "F. Jason Park" <[email protected]>
Date: Fri, 15 Jul 2022 05:02:35 -0700
Subject: [PATCH 2/6] [5.6] Make ERC's message-sending functions more flexible

* lisp/erc/erc-backend.el (erc--server-send, erc-server-send): Convert
the latter to a wrapper that calls the former, a "new" internal
generic function.  Extend `no-penalty' parameter to mean ERC will
schedule an imminent send via a timer.  Always run
`erc-server-send-queue' on a timer.
* lisp/erc/erc.el (erc-send-action, erc--send-action): Make former a
wrapper for latter, a new generic function.  The rationale is that
built-in modules should be able to elect to handle insertion
themselves.  Also fix bug involving /ME ACTIONs not having
`erc-my-nick-face' applied to the speaker.
(erc-send-message, erc--send-message): Make the former a wrapper for
the latter, a new generic function.  Since commands, like /SV, use
this function to handle their own insertion, modules can't leverage
the normal API to suppress insertion.
(erc--send-input-lines): Convert to generic function.
---
 lisp/erc/erc-backend.el | 12 +++++++++---
 lisp/erc/erc.el         | 11 +++++++++--
 2 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/lisp/erc/erc-backend.el b/lisp/erc/erc-backend.el
index 32d891cd1c6..b16824b1f73 100644
--- a/lisp/erc/erc-backend.el
+++ b/lisp/erc/erc-backend.el
@@ -1171,7 +1171,7 @@ erc-server-send
 When FORCE is non-nil, bypass flood protection so that STRING is
 sent directly without modifying the queue.  When FORCE is the
 symbol `no-penalty', exempt this round from accumulating a
-timeout penalty.
+timeout penalty and schedule it to run ASAP instead of blocking.
 
 If TARGET is specified, look up encoding information for that
 channel in `erc-encoding-coding-alist' or
@@ -1179,6 +1179,9 @@ erc-server-send
 
 See `erc-server-flood-margin' for an explanation of the flood
 protection algorithm."
+  (erc--server-send string force target))
+
+(cl-defmethod erc--server-send (string force target)
   (erc-log (concat "erc-server-send: " string "(" (buffer-name) ")"))
   (setq erc-server-last-sent-time (erc-current-time))
   (let ((encoding (erc-coding-system-for-target target)))
@@ -1199,14 +1202,17 @@ erc-server-send
                         (when (fboundp 'set-process-coding-system)
                           (set-process-coding-system erc-server-process
                                                      'raw-text encoding))
-                        (process-send-string erc-server-process str))
+                        (if (and (eq force 'no-penalty))
+                            (run-at-time nil nil #'process-send-string
+                                         erc-server-process str)
+                          (process-send-string erc-server-process str)))
                     ;; See `erc-server-send-queue' for full
                     ;; explanation of why we need this condition-case
                     (error nil)))
               (setq erc-server-flood-queue
                     (append erc-server-flood-queue
                             (list (cons str encoding))))
-              (erc-server-send-queue (current-buffer))))
+              (run-at-time nil nil #'erc-server-send-queue (current-buffer))))
           t)
       (message "ERC: No process running")
       nil)))
diff --git a/lisp/erc/erc.el b/lisp/erc/erc.el
index 2d8f388328d..a885038411d 100644
--- a/lisp/erc/erc.el
+++ b/lisp/erc/erc.el
@@ -2950,13 +2950,17 @@ erc-toggle-debug-irc-protocol
 
 (defun erc-send-action (tgt str &optional force)
   "Send CTCP ACTION information described by STR to TGT."
+  (erc--send-action tgt str force))
+
+(cl-defmethod erc--send-action (tgt str &optional force)
   (erc-send-ctcp-message tgt (format "ACTION %s" str) force)
   ;; Allow hooks that act on inserted PRIVMSG and NOTICES to process us.
   (let ((erc--msg-prop-overrides `((erc-msg . msg)
                                    (erc-ctcp . ACTION)
                                    ,@erc--msg-prop-overrides))
         (nick (erc-current-nick)))
-    (setq nick (propertize nick 'erc-speaker nick))
+    (setq nick (propertize nick 'erc-speaker nick
+                           'font-lock-face 'erc-my-nick-face))
     (erc-display-message nil '(t action input) (current-buffer)
                          'ACTION ?n nick ?a str ?u "" ?h "")))
 
@@ -4493,6 +4497,9 @@ erc-send-message
   "Send LINE to the current channel or user and display it.
 
 See also `erc-message' and `erc-display-line'."
+  (erc--send-message line force))
+
+(cl-defgeneric erc--send-message (line force)
   (erc-message "PRIVMSG" (concat (erc-default-target) " " line) force)
   (erc-display-line
    (concat (erc-format-my-nick) line)
@@ -6978,7 +6985,7 @@ erc--run-send-hooks
     (user-error "Multiline command detected" ))
   lines-obj)
 
-(defun erc--send-input-lines (lines-obj)
+(cl-defmethod erc--send-input-lines (lines-obj)
   "Send lines in `erc--input-split-lines' object LINES-OBJ."
   (when (erc--input-split-sendp lines-obj)
     (dolist (line (erc--input-split-lines lines-obj))
-- 
2.41.0

From 65bc05e03a022ed58774226bf3d3dc9f35525820 Mon Sep 17 00:00:00 2001
From: "F. Jason Park" <[email protected]>
Date: Fri, 9 Jun 2023 21:00:03 -0700
Subject: [PATCH 3/6] [5.6] Simplify logic for inserting ERC prompt input

* lisp/erc/erc.el (erc--current-line-input-split): New variable bound
to the current `erc--input-split' object, post review, for the extent
of display processing, so that "slash" commands can access it.
(erc-cmd-SAY): Defer to `erc--send-message'.
(erc--send-message): New implementation.  When called internally and
the variable `erc--current-line-input-split' is non-nil, treat input
as an outgoing message to ensure "send" hooks run and invariants for
prompt markers are preserved.  For example, this means noncommands,
like /SV will have `erc-input-face' applied, which is correct because
this message is sent to an actual target on the server.
(erc--make-input-split): New function.
(erc-send-current-line): Bind `erc--current-line-input-split' when
dispatching prompt-input handlers.  Use helper
`erc--make-input-split'.
(erc--run-send-hooks): Honor existing `refoldp' slot from
`erc--input-split' object.
---
 lisp/erc/erc.el | 50 +++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 40 insertions(+), 10 deletions(-)

diff --git a/lisp/erc/erc.el b/lisp/erc/erc.el
index a885038411d..4828319727e 100644
--- a/lisp/erc/erc.el
+++ b/lisp/erc/erc.el
@@ -3659,6 +3659,12 @@ erc--called-as-input-p
   "Non-nil when a user types a \"/slash\" command.
 Remains bound until `erc-cmd-SLASH' returns.")
 
+(defvar erc--current-line-input-split nil
+  "Current `erc--input-split' instance when processing user input.
+This is for special cases in which a \"slash\" command needs
+details about the input it's handling or needs to detect whether
+it's been dispatched by `erc-send-current-line'.")
+
 (defvar-local erc-send-input-line-function #'erc-send-input-line
   "Function for sending lines lacking a leading \"slash\" command.
 When prompt input starts with a \"slash\" command, like \"/MSG\",
@@ -3795,9 +3801,7 @@ erc-cmd-SAY
   (if (string-match "^\\s-*$" line)
       nil
     (string-match "^ ?\\(.*\\)" line)
-    (let ((msg (match-string 1 line)))
-      (erc-display-msg msg)
-      (erc-process-input-line msg nil t))))
+    (erc--send-message (match-string 1 line) nil)))
 (put 'erc-cmd-SAY 'do-not-parse-args t)
 
 (defun erc-cmd-SET (line)
@@ -4507,6 +4511,27 @@ erc--send-message
   ;; FIXME - treat multiline, run hooks, or remove me?
   t)
 
+;; When running inside insert and send hooks, take more care in
+;; dealing with the prompt.
+(cl-defmethod erc--send-message
+  (input-line force &context (erc--current-line-input-split erc--input-split))
+  "Process non-command INPUT-LINE almost as if it's normal chat input.
+Expect INPUT-LINE to differ from the `string' slot of the calling
+context's `erc--current-line-input-split' object because the
+latter is likely a slash command invocation whose handler
+generated INPUT-LINE.  Before inserting INPUT-LINE, split it and
+run `erc-send-modify-hook' and `erc-send-post-hook' on each
+actual outgoing line.  Forgo input validation because this isn't
+interactive input, and skip `erc-send-completed-hook' because it
+will run just before the outer `erc-send-current-line' call
+returns."
+  (let* ((erc-flood-protect (not force))
+         (lines-obj (erc--make-input-split input-line)))
+    (setf (erc--input-split-refoldp lines-obj) t
+          (erc--input-split-cmdp lines-obj) nil)
+    (erc--send-input-lines (erc--run-send-hooks lines-obj)))
+  t)
+
 (defun erc-cmd-MODE (line)
   "Change or display the mode value of a channel or user.
 The first word specifies the target.  The rest is the mode string
@@ -6880,6 +6905,14 @@ erc--inhibit-slash-cmd-insertion
   (when (erc--input-split-cmdp state)
     (setf (erc--input-split-insertp state) nil)))
 
+(defun erc--make-input-split (string)
+  (make-erc--input-split
+   :string string
+   :insertp erc-insert-this
+   :sendp erc-send-this
+   :lines (split-string string erc--input-line-delim-regexp)
+   :cmdp (string-match erc-command-regexp string)))
+
 (defun erc-send-current-line ()
   "Parse current line and send it to IRC."
   (interactive)
@@ -6894,16 +6927,11 @@ erc-send-current-line
             (expand-abbrev))
           (widen)
           (let* ((str (erc-user-input))
-                 (state (make-erc--input-split
-                         :string str
-                         :insertp erc-insert-this
-                         :sendp erc-send-this
-                         :lines (split-string
-                                 str erc--input-line-delim-regexp)
-                         :cmdp (string-match erc-command-regexp str))))
+                 (state (erc--make-input-split str)))
             (run-hook-with-args 'erc--input-review-functions state)
             (when-let (((not (erc--input-split-abortp state)))
                        (inhibit-read-only t)
+                       (erc--current-line-input-split state)
                        (old-buf (current-buffer)))
               (let ((erc--msg-prop-overrides `((erc-msg . msg)
                                                ,@erc--msg-prop-overrides)))
@@ -6969,6 +6997,8 @@ erc--run-send-hooks
                       (run-hook-with-args 'erc-send-pre-hook str)
                       (make-erc-input :string str
                                       :insertp erc-insert-this
+                                      :refoldp (erc--input-split-refoldp
+                                                lines-obj)
                                       :sendp erc-send-this))))
         (run-hook-with-args 'erc-pre-send-functions state)
         (setf (erc--input-split-sendp lines-obj) (erc-input-sendp state)
-- 
2.41.0

From 2aaad91082113724ccd8ad6f9b5731815ad621f5 Mon Sep 17 00:00:00 2001
From: "F. Jason Park" <[email protected]>
Date: Wed, 8 Nov 2023 21:20:54 -0800
Subject: [PATCH 4/6] [5.6] Slightly simplify text props on echoed ERC input

* lisp/erc/erc.el (erc--msg-props): Reformat doc to improve
readability.
(erc-send-current-line): Don't bind `erc--msg-prop-overrides' because
it affects all calls to `erc-display-message' made by slash commands,
etc.
(erc-display-msg): Set `erc-msg' property to `msg' instead of `self'
because the only legitimate use of this function is for inserting
"echoed" prompt input.  (Bug#60936)
---
 lisp/erc/erc.el | 39 +++++++++++++++++----------------------
 1 file changed, 17 insertions(+), 22 deletions(-)

diff --git a/lisp/erc/erc.el b/lisp/erc/erc.el
index 4828319727e..be8e2d19b7f 100644
--- a/lisp/erc/erc.el
+++ b/lisp/erc/erc.el
@@ -155,31 +155,28 @@ erc--msg-props
 as of ERC 5.6:
 
  - `erc-msg': a symbol, guaranteed present; values include:
-
-   - `msg', signifying a `PRIVMSG' or an incoming `NOTICE'
-   - `self', a fallback used by `erc-display-msg' for callers
-     that don't specify an `erc-msg'
-   - `unknown', a similar fallback for `erc-display-message'
-   - a catalog key, such as `s401' or `finished'
-   - an `erc-display-message' TYPE parameter, like `notice'
+   `msg', signifying a `PRIVMSG' or an incoming `NOTICE';
+   `unknown', a fallback for `erc-display-message'; a catalog
+    key, such as `s401' or `finished'; an `erc-display-message'
+    TYPE parameter, like `notice'
 
  - `erc-cmd': a message's associated IRC command, as read by
    `erc--get-eq-comparable-cmd'; currently either a symbol, like
    `PRIVMSG', or a number, like 5, which represents the numeric
-   \"005\"; absent on \"local\" messages, such as simple warnings
-   and help text, and on outgoing messages unless echoed back by
-   the server (assuming future support)
+    \"005\"; absent on \"local\" messages, such as simple warnings
+    and help text, and on outgoing messages unless echoed back by
+    the server (assuming future support)
 
  - `erc-ctcp': a CTCP command, like `ACTION'
 
  - `erc-ts': a timestamp, possibly provided by the server; as of
-   5.6, a ticks/hertz pair on Emacs 29 and above, and a \"list\"
-   type otherwise; managed by the `stamp' module
+    5.6, a ticks/hertz pair on Emacs 29 and above, and a \"list\"
+    type otherwise; managed by the `stamp' module
 
  - `erc-ephemeral': a symbol prefixed by or matching a module
-   name; indicates to other modules and members of modification
-   hooks that the current message should not affect stateful
-   operations, such as recording a channel's most recent speaker
+    name; indicates to other modules and members of modification
+    hooks that the current message should not affect stateful
+    operations, such as recording a channel's most recent speaker
 
 This is an internal API, and the selection of related helper
 utilities is fluid and provisional.  As of ERC 5.6, see the
@@ -6933,8 +6930,7 @@ erc-send-current-line
                        (inhibit-read-only t)
                        (erc--current-line-input-split state)
                        (old-buf (current-buffer)))
-              (let ((erc--msg-prop-overrides `((erc-msg . msg)
-                                               ,@erc--msg-prop-overrides)))
+              (progn ; unprogn this during next major surgery
                 (erc-set-active-buffer (current-buffer))
                 ;; Kill the input and the prompt
                 (delete-region erc-input-marker (erc-end-of-input-line))
@@ -7079,16 +7075,15 @@ erc-send-input
 
 (defun erc-display-msg (line)
   "Insert LINE into current buffer and run \"send\" hooks.
-Expect LINE to originate from input submitted interactively at
-the prompt, such as outgoing chat messages or echoed slash
-commands."
+Treat LINE as input submitted interactively at the prompt, such
+as outgoing chat messages and echoed slash commands."
   (when erc-insert-this
     (save-excursion
       (erc--assert-input-bounds)
       (let ((insert-position (marker-position (goto-char erc-insert-marker)))
-            (erc--msg-props (or erc--msg-props ; prefer `self' to `unknown'
+            (erc--msg-props (or erc--msg-props
                                 (let ((ovs erc--msg-prop-overrides))
-                                  (map-into `((erc-msg . self) ,@(reverse ovs))
+                                  (map-into `((erc-msg . msg) ,@(reverse ovs))
                                             'hash-table))))
             beg)
         (insert (erc-format-my-nick))
-- 
2.41.0

From e7f166024092087721269f7bdab9153fceec08ec Mon Sep 17 00:00:00 2001
From: "F. Jason Park" <[email protected]>
Date: Thu, 9 Nov 2023 10:37:49 -0800
Subject: [PATCH 5/6] [5.6] Don't output non-modules in erc-modes

* lisp/erc/erc.el (erc-modes): Only list actual modules created via
`define-erc-module.  Also `quote' members of the resulting list.
---
 lisp/erc/erc.el | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lisp/erc/erc.el b/lisp/erc/erc.el
index be8e2d19b7f..00ee97b7e14 100644
--- a/lisp/erc/erc.el
+++ b/lisp/erc/erc.el
@@ -8135,8 +8135,9 @@ erc-modes
                     (let (modes (case-fold-search nil))
                       (dolist (var (apropos-internal "^erc-.*mode$"))
                         (when (and (boundp var)
+                                   (get var 'erc-module)
                                    (symbol-value var))
-                          (setq modes (cons (symbol-name var)
+                          (setq modes (cons (concat "`" (symbol-name var) "'")
                                             modes))))
                       modes)
                     ", ")))
-- 
2.41.0

From 96b62219e43df0585ddfbabaa904342ca0385d22 Mon Sep 17 00:00:00 2001
From: "F. Jason Park" <[email protected]>
Date: Fri, 10 Nov 2023 13:34:31 -0800
Subject: [PATCH 6/6] [5.6] Revive erc-display-command as module
 command-indicator

* lisp/erc/erc-goodies.el (erc-noncommands-list): Replace the
nonexistent `erc-cmd-SMV' with `erc-cmd-SAY'.
(erc-noncommands-mode, erc-noncommands-enable,
erc-noncommands-disable): Deprecate.
(erc-command-indicator-face, erc-command-indicator): Migrate from main
library.
(erc-command-indicator-mode, erc-command-indicator-enable,
erc-command-indicator-disable): New module to take the place of
`noncommands'.
(erc-command-indicator-toggle-hidden): New command to toggle echoed
command-line visibility.
(erc--command-indicator-permit-insertion): New function.
(erc--command-indicator-display): New function, a slightly revised
version of the old `erc-display-command' from the main library.  Its
only call site was removed back in d1036d288de "backport: erc
bugfixes".  However, references were left behind to associated assets,
like `erc-command-indicator', etc.  The function was later commented
out in 0c599ee2e2c "* lisp/erc/erc.el: Use `run-hook-with-args` for
`erc-pre-send-functions`", and then removed by a63ed6f78a6 "Remove
duplicate ERC prompt on reconnect".
* lisp/erc/erc-match.el (erc-match-toggle-hidden-fools): Use new
non-module-specific name for `erc-match--toggle-hidden'.
(erc-match--toggle-hidden): Move to main library for shared use by
other modules.
* lisp/erc/erc.el (erc-hide-prompt): Leave note explaining updated
role.
(erc-command-indicator): Move to erc-goodies.
(erc-command-indicator-face): Move to erc-goodies.
(erc-modules): Remove module `noncommands' from standard value.
(erc--toggle-hidden): "New" function, a rebranded version of
`erc-match--toggle-hidden'.
(erc--send-input-lines): Accommodate modules wanting alternate
insertion functions.
(erc-load-irc-script-lines): Account for `erc-command-indicator' no
longer being defined in this library.
* test/lisp/erc/erc-tests.el (erc-tests--modules): Remove
deprecated module `noncommands' from manifest.  (Bug#67031)
---
 etc/ERC-NEWS               |  15 +++++
 lisp/erc/erc-goodies.el    | 113 ++++++++++++++++++++++++++++++++++---
 lisp/erc/erc-match.el      |  14 +----
 lisp/erc/erc.el            |  63 ++++++++++-----------
 test/lisp/erc/erc-tests.el |   3 +-
 5 files changed, 152 insertions(+), 56 deletions(-)

diff --git a/etc/ERC-NEWS b/etc/ERC-NEWS
index f59023eae62..49b623aa7f0 100644
--- a/etc/ERC-NEWS
+++ b/etc/ERC-NEWS
@@ -157,6 +157,21 @@ asking users who've customized this option to switch to
 that some other solution, like automatic migration, is justified,
 please make that known on the bug list.
 
+** Module 'noncommands' deprecated, replaced by 'command-indicator'.
+Command-line echoing has returned to ERC after a near-decade-long
+hiatus.  This means you can elect to have ERC leave a trail of most
+slash-command input submitted at the prompt, in a manner resembling a
+shell or a REPL.  The particulars are likely of little interest to
+most users, but the gist is that this functionality was removed in
+5.3.x (Emacs 24.5) under mysterious circumstances, without mention in
+this document or any change log.  Everything's mostly been restored,
+except that the feature is now opt-in.  (Add 'command-indicator' to
+'erc-modules' to get started.)  The only real gotcha is that related
+faces and options, like 'erc-command-indicator', have moved to the
+'erc-goodies' library, although their Custom groups remain the same.
+Hint: once enabled, use 'erc-command-indicator-toggle-hidden' to
+dynamically toggle echoed command-line visibility.
+
 ** 'erc-button-alist' and 'erc-nick-popup-alist' have evolved slightly.
 It's no secret that the 'buttons' module treats potential nicknames
 specially.  This is perhaps most evident in its treatment of the
diff --git a/lisp/erc/erc-goodies.el b/lisp/erc/erc-goodies.el
index 4cc81dd9378..93b76c544aa 100644
--- a/lisp/erc/erc-goodies.el
+++ b/lisp/erc/erc-goodies.el
@@ -471,21 +471,26 @@ erc-noncommands-list
                                erc-cmd-COUNTRY
                                erc-cmd-SV
                                erc-cmd-SM
-                               erc-cmd-SMV
+                               erc-cmd-SAY
                                erc-cmd-LASTLOG)
-  "List of commands that are aliases for CTCP ACTION or for ERC messages.
-
-If a command's function symbol is in this list, the typed command
-does not appear in the ERC buffer after the user presses ENTER.")
+  "List of commands that perform their own buffer I/O.
+The `command-indicator' module forgoes echoing commands in this
+list.")
 
 ;;;###autoload(autoload 'erc-noncommands-mode "erc-goodies" nil t)
 (define-erc-module noncommands nil
-  "This mode distinguishes non-commands.
-Commands listed in `erc-insert-this' know how to display
-themselves."
+  "Treat commands that display themselves specially.
+This module has been a no-op since ERC 5.3 and has likely only
+ever made sense in the context of `erc-command-indicator'.  It
+was deprecated in ERC 5.6."
   ((add-hook 'erc--input-review-functions #'erc-send-distinguish-noncommands))
   ((remove-hook 'erc--input-review-functions
                 #'erc-send-distinguish-noncommands)))
+(make-obsolete-variable 'erc-noncommand-mode
+                        'erc-command-indicator-mode "30.1")
+(make-obsolete 'erc-noncommand-mode 'erc-command-indicator-mode "30.1")
+(make-obsolete 'erc-noncommand-enable 'erc-command-indicator-enable "30.1")
+(make-obsolete 'erc-noncommand-disable 'erc-command-indicator-disable "30.1")
 
 (defun erc-send-distinguish-noncommands (state)
   "If STR is an ERC non-command, set `insertp' in STATE to nil."
@@ -499,6 +504,98 @@ erc-send-distinguish-noncommands
       ;; Inhibit sending this string.
       (setf (erc-input-insertp state) nil))))
 
+
+;;; Command-indicator
+
+(defface erc-command-indicator-face
+  '((t :inherit (shadow fixed-pitch-serif)))
+  "Face for echoed command lines, including the prompt.
+See option `erc-command-indicator'."
+  :package-version '(ERC . "5.6")
+  :group 'erc-faces)
+
+(defcustom erc-command-indicator "$>"
+  "Pseudo prompt for echoed command lines.
+An analog of the option `erc-prompt' that replaces the \"speaker
+label\" for echoed \"slash\" commands submitted at the prompt.  A
+value of nil means ERC only inserts the command line portion,
+sans pseudo prompt, which may trick certain modules into treating
+the slash command itself as the message's \"speaker\"."
+  :package-version '(ERC . "5.6")
+  :group 'erc-display
+  :type '(choice (const "$>") (const nil) string function))
+
+;;;###autoload(autoload 'erc-command-indicator-mode "erc-goodies" nil t)
+(define-erc-module command-indicator nil
+  "Echo command lines for \"slash commands,\" like /JOIN, /HELP, etc.
+Skip those appearing in `erc-noncommands-list'.
+
+Users can run \\[erc-command-indicator-toggle-hidden] to hide and
+reveal echoed command lines after they've been inserted."
+  ((add-hook 'erc--input-review-functions
+             #'erc--command-indicator-permit-insertion 90 t)
+   (erc-command-indicator-toggle-hidden -1))
+  ((remove-hook 'erc--input-review-functions
+                #'erc--command-indicator-permit-insertion t)
+   (erc-command-indicator-toggle-hidden +1))
+  'local)
+
+(defun erc-command-indicator ()
+  "Return the command-indicator prompt as a string.
+Do nothing if the variable `erc-command-indicator' is nil."
+  (and erc-command-indicator
+       (let ((prompt (if (functionp erc-command-indicator)
+                         (funcall erc-command-indicator)
+                       erc-command-indicator)))
+         (concat prompt (and (not (string-empty-p prompt)) " ")))))
+
+(defun erc-command-indicator-toggle-hidden (arg)
+  "Toggle whether echoed \"slash commands\" are visible."
+  (interactive "P")
+  (erc--toggle-hidden 'command-indicator arg))
+
+(defun erc--command-indicator-permit-insertion (state)
+  "Insert `erc-input' STATE's message if it's an echoed command."
+  (cl-assert erc-command-indicator-mode)
+  (when (erc--input-split-cmdp state)
+    (setf (erc--input-split-insertp state) #'erc--command-indicator-display)
+    (erc-send-distinguish-noncommands state)))
+
+;; That function used to be called `erc-display-command'.  It was
+;; neutered in ERC 5.3.x (Emacs 24.5), commented out in 5.4, removed
+;; in 5.5, and restored in 5.6.
+(defun erc--command-indicator-display (line)
+  "Insert command LINE as echoed input resembling that of REPLs and shells."
+  (when erc-insert-this
+    (save-excursion
+      (erc--assert-input-bounds)
+      (let ((insert-position (marker-position (goto-char erc-insert-marker)))
+            (erc--msg-props (or erc--msg-props
+                                (let ((ovs erc--msg-prop-overrides))
+                                  (map-into `((erc-msg . slash-cmd)
+                                              ,@(reverse ovs))
+                                            'hash-table)))))
+        (when-let ((string (erc-command-indicator))
+                   (erc-input-marker (copy-marker erc-input-marker)))
+          (erc-display-prompt nil nil string 'erc-command-indicator-face)
+          (set-marker erc-input-marker nil))
+        (let ((beg (point)))
+          (insert line)
+          (erc-put-text-property beg (point)
+                                 'font-lock-face 'erc-command-indicator-face)
+          (insert "\n"))
+        (save-restriction
+          (narrow-to-region insert-position (point))
+          (run-hooks 'erc-send-modify-hook)
+          (run-hooks 'erc-send-post-hook)
+          (cl-assert (> (- (point-max) (point-min)) 1))
+          (erc--hide-message 'command-indicator)
+          (add-text-properties (point-min) (1+ (point-min))
+                               (erc--order-text-properties-from-hash
+                                erc--msg-props))))
+      (erc--refresh-prompt))))
+
+
 ;;; IRC control character processing.
 (defgroup erc-control-characters nil
   "Dealing with control characters."
diff --git a/lisp/erc/erc-match.el b/lisp/erc/erc-match.el
index 8644e61106f..6fff54d3cf4 100644
--- a/lisp/erc/erc-match.el
+++ b/lisp/erc/erc-match.el
@@ -695,19 +695,7 @@ erc-match-toggle-hidden-fools
 Expect the function `erc-hide-fools' or similar to be present in
 `erc-text-matched-hook'."
   (interactive "P")
-  (erc-match--toggle-hidden 'match-fools arg))
-
-(defun erc-match--toggle-hidden (prop arg)
-  "Toggle invisibility for spec member PROP.
-Treat ARG in a manner similar to mode toggles defined by
-`define-minor-mode'."
-  (when arg
-    (setq arg (prefix-numeric-value arg)))
-  (if (memq prop (ensure-list buffer-invisibility-spec))
-      (unless (natnump arg)
-        (remove-from-invisibility-spec prop))
-    (when (or (not arg) (natnump arg))
-      (add-to-invisibility-spec prop))))
+  (erc--toggle-hidden 'match-fools arg))
 
 (provide 'erc-match)
 
diff --git a/lisp/erc/erc.el b/lisp/erc/erc.el
index 00ee97b7e14..89b3397d8f1 100644
--- a/lisp/erc/erc.el
+++ b/lisp/erc/erc.el
@@ -346,8 +346,13 @@ erc-hide-prompt
   "If non-nil, hide input prompt upon disconnecting.
 To unhide, type something in the input area.  Once revealed, a
 prompt remains unhidden until the next disconnection.  Channel
-prompts are unhidden upon rejoining.  See
-`erc-unhide-query-prompt' for behavior concerning query prompts."
+prompts are unhidden upon rejoining.  For behavior concerning
+query prompts, see `erc-unhide-query-prompt'.  Longtime ERC users
+should note that this option was repurposed in ERC 5.5 because it
+had lain dormant for years after being sidelined in 5.3 when its
+only use in the interactive client was removed.  Before then, its
+role was controlling whether `erc-command-indicator' would appear
+alongside echoed slash-command lines."
   :package-version '(ERC . "5.5")
   :group 'erc-display
   :type '(choice (const :tag "Always hide prompt" t)
@@ -759,28 +764,6 @@ erc-prompt
         (concat prompt " ")
       prompt)))
 
-(defcustom erc-command-indicator nil
-  "Indicator used by ERC for showing commands.
-
-If non-nil, this will be used in the ERC buffer to indicate
-commands (i.e., input starting with a `/').
-
-If nil, the prompt will be constructed from the variable `erc-prompt'."
-  :group 'erc-display
-  :type '(choice (const nil) string function))
-
-(defun erc-command-indicator ()
-  "Return the command indicator prompt as a string.
-
-This only has any meaning if the variable `erc-command-indicator' is non-nil."
-  (and erc-command-indicator
-       (let ((prompt (if (functionp erc-command-indicator)
-                         (funcall erc-command-indicator)
-                       erc-command-indicator)))
-         (if (> (length prompt) 0)
-             (concat prompt " ")
-           prompt))))
-
 (defcustom erc-notice-prefix "*** "
   "Prefix for all notices."
   :group 'erc-display
@@ -1364,12 +1347,6 @@ erc-prompt-face
   "ERC face for the prompt."
   :group 'erc-faces)
 
-(defface erc-command-indicator-face
-  '((t :weight bold))
-  "ERC face for the command indicator.
-See the variable `erc-command-indicator'."
-  :group 'erc-faces)
-
 (defface erc-notice-face
   '((default :weight bold)
     (((class color) (min-colors 88) (supports :weight semi-bold))
@@ -2077,7 +2054,7 @@ erc--sort-modules
 
 (defcustom erc-modules '( autojoin button completion fill imenu irccontrols
                           list match menu move-to-prompt netsplit
-                          networks noncommands readonly ring stamp track)
+                          networks readonly ring stamp track)
   "A list of modules which ERC should enable.
 If you set the value of this without using `customize' remember to call
 \(erc-update-modules) after you change it.  When using `customize', modules
@@ -2127,6 +2104,7 @@ erc-modules
     (const :tag "button: Buttonize URLs, nicknames, and other text" button)
     (const :tag "capab: Mark unidentified users on servers supporting CAPAB"
            capab-identify)
+    (const :tag "command-indicator: Echo command lines." command-indicator)
     (const :tag "completion: Complete nicknames and commands (programmable)"
            completion)
     (const :tag "dcc: Provide Direct Client-to-Client support" dcc)
@@ -2146,7 +2124,7 @@ erc-modules
     (const :tag "networks: Provide data about IRC networks" networks)
     (const :tag "nickbar: Show nicknames in a dyamic side window" nickbar)
     (const :tag "nicks: Uniquely colorize nicknames in target buffers" nicks)
-    (const :tag "noncommands: Don't display non-IRC commands after evaluation"
+    (const :tag "noncommands: Deprecated. See module `command-indicator'."
            noncommands)
     (const :tag "notifications: Desktop alerts on PRIVMSG or mentions"
            notifications)
@@ -3309,6 +3287,18 @@ erc--hide-message
           (cl-incf beg))
         (erc--merge-prop (1- beg) (1- end) 'invisible value)))))
 
+(defun erc--toggle-hidden (prop arg)
+  "Toggle invisibility for spec member PROP.
+Treat ARG in a manner similar to mode toggles defined by
+`define-minor-mode'."
+  (when arg
+    (setq arg (prefix-numeric-value arg)))
+  (if (memq prop (ensure-list buffer-invisibility-spec))
+      (unless (natnump arg)
+        (remove-from-invisibility-spec prop))
+    (when (or (not arg) (natnump arg))
+      (add-to-invisibility-spec prop))))
+
 (defun erc--delete-inserted-message (beg-or-point &optional end)
   "Remove message between BEG and END.
 Expect BEG and END to match bounds as returned by the macro
@@ -7016,7 +7006,9 @@ erc--send-input-lines
   (when (erc--input-split-sendp lines-obj)
     (dolist (line (erc--input-split-lines lines-obj))
       (when (erc--input-split-insertp lines-obj)
-        (erc-display-msg line))
+        (if (functionp (erc--input-split-insertp lines-obj))
+            (funcall (erc--input-split-insertp lines-obj) line)
+          (erc-display-msg line)))
       (erc-process-input-line (concat line "\n")
                               (null erc-flood-protect)
                               (not (erc--input-split-cmdp lines-obj))))))
@@ -7522,7 +7514,10 @@ erc-load-irc-script-lines
 user input."
   (let* ((cb (current-buffer))
          (s "")
-         (sp (or (erc-command-indicator) (erc-prompt)))
+         (sp (or (and (bound-and-true-p erc-command-indicator-mode)
+                      (fboundp 'erc-command-indicator)
+                      (erc-command-indicator))
+                 (erc-prompt)))
          (args (and (boundp 'erc-script-args) erc-script-args)))
     (if (and args (string-match "^ " args))
         (setq args (substring args 1)))
diff --git a/test/lisp/erc/erc-tests.el b/test/lisp/erc/erc-tests.el
index 2898ca7be75..e7422d330c0 100644
--- a/test/lisp/erc/erc-tests.el
+++ b/test/lisp/erc/erc-tests.el
@@ -2543,7 +2543,8 @@ erc-handle-irc-url
     (kill-buffer "#chan")))
 
 (defconst erc-tests--modules
-  '( autoaway autojoin bufbar button capab-identify completion dcc fill identd
+  '( autoaway autojoin bufbar button capab-identify
+     command-indicator completion dcc fill identd
      imenu irccontrols keep-place list log match menu move-to-prompt netsplit
      networks nickbar nicks noncommands notifications notify page readonly
      replace ring sasl scrolltobottom services smiley sound
-- 
2.41.0