Crystallize erc-nicks-track-faces behavior

* etc/ERC-NEWS: Mention changes to `erc-track-faces-normal-list' and
`erc-track-faces-priority-list'.  Also mention new choice variant for
option `erc-nicks-track-faces', although that's arguably just a bug fix
because it makes good on previously unrealized behavior implied by the
doc strings.
* lisp/erc/erc-nicks.el (erc-nicks-skip-faces): Remove faces applied by
the `match' module, namely, `erc-current-nick-face', `erc-pal-face', and
`erc-fool-face'.  That module runs its hooks after `button' on
`erc-insert-modify-hook', and because `nicks' piggybacks on `button', it
can never encounter those faces while assaying.
(erc-nicks-track-faces): Update doc, and introduce new `t' value choice.
(erc-nicks-mode, erc-nicks-disable): Update removals from
`erc-track--alt-normals-function' to reflect recent renamings.
(erc-nicks--reject-uninterned-faces): Use helper.
(erc-nicks--oursp, erc-nicks--ours-p): Rename former to latter to
respect project style guidelines regarding predicates.
(erc-nicks-track-normal-max-rank): New variable.
(erc-nicks--check-normals, erc-nicks--assess-track-faces): Rename former
to latter, and change purpose to checking for "normals" membership,
ranks position, and incumbent face ownership.  Remove unused CONTENDERS
parameter.  Additionally, change behavior to consider replacing the
current mode-line face when it's not `nicks' owned if it's explicitly
ranked lower than `erc-default-face'.
(erc-nicks--track-prioritize, erc-nicks--track-always): New
complementary functions implementing the t and `prioritize' variants of
`erc-nicks-track-faces'.  Both make use of the factored-out
`erc-nicks--check-normals' logic.
(erc-nicks--setup-track-integration): Add `erc-nicks--track-always' to
`erc-track--alt-normals-function' when `erc-track-normal-faces' is t.
* lisp/erc/erc-track.el (erc-track--massage-nick-button-faces): Change
type of symbol property `erc-track--obsolete-faces' for options
`erc-track-faces-priority-list' and friends from a boolean to an alist.
(erc-track-faces-priority-list): Add new face for buttonized speakers.
(erc-track-faces-normal-list): Add new face for buttonized speakers.
Also add `erc-notice-face'.
(erc-track--priority-faces): New local variable to cache ranked faces
and complement `erc-track--normal-faces'.
(erc-track--setup): Initialize new `erc-track--priority-faces' variable,
and refactor.
(erc-track--alt-normals-function): Doc.
(erc-track--select-mode-line-face): Update expected type of `ranks'
parameter.
(erc-track-modified-channels): Fix wrong-type bug occurring when
`erc-track-ignore-normal-contenders-p' and
`erc-track-priority-faces-only' are both non-nil.  Also fix subtle
compatibility oversight regarding an empty face list returned by
`erc-track--collect-faces-in'.
* test/lisp/erc/erc-nicks-tests.el: Load helpers and fixtures library.
(erc-nicks-tests--track-faces): New function.
(erc-nicks-track-faces/prioritize, erc-nicks-track-faces/defer)
(erc-nicks-track-faces/nil, erc-nicks-track-faces/t): New tests.
* test/lisp/erc/erc-track-tests.el
(erc-track-tests--select-mode-line-face): Update expected type of mocked
parameter.
(erc-track-tests--modified-channels/baseline): New function.
(erc-track-modified-channels/baseline)
(erc-track-modified-channels/baseline/mention)
(erc-track-modified-channels/baseline/ignore)
(erc-track-modified-channels/baseline/mention/ignore)
(erc-track-modified-channels/priority-only-all/baseline)
(erc-track-modified-channels/priority-only-all/sans-notice): New tests.
* test/lisp/erc/resources/erc-tests-common.el
(erc-tests-common-track-modified-channels)
(erc-tests-common-track-modified-channels-sans-setup): New functions.
(Bug67767)

2 files changed, 203 insertions, 108 deletions

diff --git a/lisp/erc/erc-nicks.el b/lisp/erc/erc-nicks.el
index a0d6d17d732..6282242f4ac 100644
--- a/lisp/erc/erc-nicks.el
+++ b/lisp/erc/erc-nicks.el
@@ -89,10 +89,10 @@ ERC only considers this option during module activation, so users
 should adjust it before connecting."
   :type '(repeat string))
 
-(defcustom erc-nicks-skip-faces '( erc-notice-face erc-current-nick-face
-                                   erc-my-nick-face erc-pal-face erc-fool-face)
+(defcustom erc-nicks-skip-faces '(erc-notice-face erc-my-nick-face)
   "Faces to avoid highlighting atop."
-  :type  (erc--with-dependent-type-match (repeat face) erc-match))
+  :type '(repeat face)
+  :package-version '(ERC . "5.6.1"))
 
 (defcustom erc-nicks-backing-face erc-button-nickname-face
   "Face to mix with generated one for emphasizing non-speakers."
@@ -175,17 +175,20 @@ like \"@%-012n\"."
 
 (defcustom erc-nicks-track-faces 'prioritize
   "Show nick faces in the `track' module's portion of the mode line.
-A value of nil means don't show nick faces at all.  A value of
-`defer' means have `track' consider nick faces only after those
-ranked faces in `erc-track-faces-normal-list'.  This has the
-effect of \"alternating\" between a ranked \"normal\" and a nick.
-The value `prioritize' means have `track' consider nick faces to
-be \"normal\" unless the current speaker is the same as the
-previous one, in which case pretend the value is `defer'.  Like
-most options in this module, updating the value mid-session is
-not officially supported, although cycling \\[erc-nicks-mode] may
-be worth a shot."
-  :type '(choice (const nil) (const defer) (const prioritize)))
+A value of nil means don't show `nicks'-managed faces at all.  A value
+of t means treat them as non-\"normal\" faces ranked at or below
+`erc-default-face'.  This has the effect of always showing them while
+suppressing the \"alternating\" behavior normally associated with
+`erc-track-faces-normal-list' (including between the speaker and nicks
+mentioned in the message body.)  A value of `defer' means treat nicks as
+unranked normals to favor alternating between them and ranked normals.
+A value of `prioritize' exhibits the same alternating effect as `defer'
+when speakers stay the same but allows a new speaker's face to
+impersonate a ranked normal so that adjacent speakers alternate among
+themselves before deferring to non-face normals.  Like most options in
+this module, updating the value mid-session is not officially supported,
+although cycling \\[erc-nicks-mode] may be worth a shot."
+  :type '(choice boolean (const defer) (const prioritize)))
 
 (defvar erc-nicks--max-skip-search 3 ; make this an option?
   "Max number of faces to visit when testing `erc-nicks-skip-faces'.")
@@ -597,7 +600,9 @@ Abandon search after examining LIMIT faces."
    (remove-function (local 'erc-button--modify-nick-function)
                     #'erc-nicks--highlight-button)
    (remove-function (local 'erc-track--alt-normals-function)
-                    #'erc-nicks--check-normals)
+                    #'erc-nicks--track-prioritize)
+   (remove-function (local 'erc-track--alt-normals-function)
+                    #'erc-nicks--track-always)
    (remove-hook 'erc-track-mode-hook #'erc-nicks--setup-track-integration t)
    (setf (alist-get "Edit face"
                     erc-button--nick-popup-alist nil 'remove #'equal)
@@ -724,31 +729,57 @@ Expect PREFIX to be something like \"ansi-color-\" or \"font-lock-\"."
               ((facep next))
               ((not (intern-soft next))))
     (setq candidate (cdr candidate)))
-  (if (and (consp candidate) (not (cdr candidate))) (car candidate) candidate))
+  (erc--solo candidate))
 
-(define-inline erc-nicks--oursp (face)
+(define-inline erc-nicks--ours-p (face)
+  "Return uninterned `nicks'-created face if FACE is a known list of faces."
   (inline-quote
    (and-let* ((sym (car-safe ,face))
               ((symbolp sym))
               ((get sym 'erc-nicks--key)))
      sym)))
 
-(defun erc-nicks--check-normals (current contender contenders normals)
-  "Return a viable `nicks'-owned face from NORMALS in CONTENDERS.
-But only do so if the CURRENT face is also one of ours and in
-NORMALS and if the highest ranked CONTENDER among new faces is
-`erc-default-face'."
-  (and-let* (((eq contender 'erc-default-face))
-             ((or (null current) (gethash current normals)))
-             (spkr (or (null current) (erc-nicks--oursp current))))
+(defvar erc-nicks-track-normal-max-rank 'erc-default-face
+  "Highest priority normal face still eligible to alternate with `nicks' faces.
+Must appear in both `erc-track-faces-priority-list' and
+`erc-track-faces-normal-list'.")
+
+(defun erc-nicks--assess-track-faces (current contender ranks normals)
+  "Return symbol face for CURRENT or t, to mean CURRENT is replaceable.
+But only do so if CURRENT and CONTENDER are either nil or \"normal\"
+faces ranking at or below `erc-nicks-track-normal-max-rank'.  See
+`erc-track--select-mode-line-face' for the expected types of RANKS and
+NORMALS.  Expect a non-nil CONTENDER to always be ranked."
+  (and-let*
+      (((or (null contender) (gethash contender normals)))
+       ((or (null current) (gethash current normals)))
+       (threshold (gethash erc-nicks-track-normal-max-rank (car ranks)))
+       ((or (null contender) (<= threshold (gethash contender (car ranks)))))
+       ((or (erc-nicks--ours-p current)
+            (null current)
+            (<= threshold (or (gethash current (car ranks)) 0)))))))
+
+(defun erc-nicks--track-prioritize (current contender contenders ranks normals)
+  "Return a viable non-CURRENT `nicks' face among CONTENDERS.
+See `erc-track--select-mode-line-face' for parameter types."
+  (when-let
+      ((spkr (erc-nicks--assess-track-faces current contender ranks normals)))
     (catch 'contender
-      (dolist (candidate (cdr contenders) contender)
+      (dolist (candidate (cdr contenders))
         (when-let (((not (equal candidate current)))
-                   ((gethash candidate normals))
-                   (s (erc-nicks--oursp candidate))
+                   (s (erc-nicks--ours-p candidate))
                    ((not (eq s spkr))))
           (throw 'contender candidate))))))
 
+(defun erc-nicks--track-always (current contender contenders ranks normals)
+  "Return a viable `nicks' face, possibly CURRENT, among CONTENDERS.
+See `erc-track--select-mode-line-face' for parameter types."
+  (when (erc-nicks--assess-track-faces current contender ranks normals)
+    (catch 'contender
+      (dolist (candidate (reverse (cdr contenders)))
+        (when (erc-nicks--ours-p candidate)
+          (throw 'contender candidate))))))
+
 (defun erc-nicks--setup-track-integration ()
   "Restore traditional \"alternating normal\" face functionality to mode-line."
   (when (bound-and-true-p erc-track-mode)
@@ -756,7 +787,10 @@ NORMALS and if the highest ranked CONTENDER among new faces is
       ;; Variant `defer' is handled elsewhere.
       ('prioritize
        (add-function :override (local 'erc-track--alt-normals-function)
-                     #'erc-nicks--check-normals))
+                     #'erc-nicks--track-prioritize))
+      ('t
+       (add-function :override (local 'erc-track--alt-normals-function)
+                     #'erc-nicks--track-always))
       ('nil
        (add-function :override (local 'erc-track--face-reject-function)
                      #'erc-nicks--reject-uninterned-faces)))))
diff --git a/lisp/erc/erc-track.el b/lisp/erc/erc-track.el
index f40960e4a22..82e5f402910 100644
--- a/lisp/erc/erc-track.el
+++ b/lisp/erc/erc-track.el
@@ -161,25 +161,33 @@ The faces used are the same as used for text in the buffers.
 \(e.g. `erc-pal-face' is used if a pal sent a message to that channel.)"
   :type 'boolean)
 
+;; In an emergency, users can opt out of this migration with:
+;;
+;;   (put 'erc-track-faces-priority-list 'erc-track--obsolete-faces t)
+;;   (put 'erc-track-faces-normal-list 'erc-track--obsolete-faces t)
+;;
 (defun erc-track--massage-nick-button-faces (sym val &optional set-fn)
-  "Transform VAL of face-list option SYM to have new defaults.
-Use `set'-compatible SET-FN when given.  If an update was
-performed, set the symbol property `erc-track--obsolete-faces' of
-SYM to t."
-  (let* ((changedp nil)
-         (new (mapcar
-               (lambda (f)
-                 (if (and (eq (car-safe f) 'erc-nick-default-face)
-                          (equal f '(erc-nick-default-face erc-default-face)))
-                     (progn
-                       (setq changedp t)
-                       (put sym 'erc-track--obsolete-faces t)
-                       (cons 'erc-button-nick-default-face (cdr f)))
-                   f))
-               val)))
-    (if set-fn
-        (funcall set-fn sym (if changedp new val))
-      (set-default sym (if changedp new val)))))
+  "Transform VAL of face-list option SYM to remove/replace obsolete items.
+Use `set'-compatible SET-FN when given.  Record any migrations as cons
+cells of (OLD . NEW) in the symbol property `erc-track--obsolete-faces'
+of SYM."
+  (let* ((oldface '(erc-nick-default-face erc-default-face))
+         (newface '(erc-button-nick-default-face erc-default-face))
+         (migrations (get sym 'erc-track--obsolete-faces))
+         (new (if migrations
+                  val
+                (delq nil
+                      (mapcar
+                       (lambda (f)
+                         (if (equal f oldface)
+                             (setf (alist-get oldface migrations
+                                              nil nil #'equal)
+                                   (and (not (member newface val)) newface))
+                           f))
+                       val)))))
+    (when migrations
+      (put sym 'erc-track--obsolete-faces migrations))
+    (if set-fn (funcall set-fn sym new) (set-default sym new))))
 
 (defcustom erc-track-faces-priority-list
   '(erc-error-face
@@ -191,6 +199,7 @@ SYM to t."
     (erc-button erc-default-face)
     erc-dangerous-host-face
     erc-nick-default-face
+    (erc-button-nick-default-face erc-nick-default-face)
     (erc-button-nick-default-face erc-default-face)
     erc-default-face
     erc-action-face
@@ -204,7 +213,7 @@ be highlighted using that face.  The first matching face is used.
 
 Note that ERC prioritizes certain faces reserved for critical
 messages regardless of this option's value."
-  :package-version '(ERC . "5.6")
+  :package-version '(ERC . "5.6.1")
   :set #'erc-track--massage-nick-button-faces
   :type (erc--with-dependent-type-match
          (repeat (choice face (repeat :tag "Combination" face)))
@@ -229,8 +238,10 @@ setting this variable might not be very useful."
   '((erc-button erc-default-face)
     erc-dangerous-host-face
     erc-nick-default-face
+    (erc-button-nick-default-face erc-nick-default-face)
     (erc-button-nick-default-face erc-default-face)
     erc-default-face
+    erc-notice-face
     erc-action-face)
   "A list of faces considered to be part of normal conversations.
 This list is used to highlight active buffer names in the mode line.
@@ -246,7 +257,7 @@ module.  To see your changes reflected mid-session, cycle
 \\[erc-track-mode].
 
 The effect may be disabled by setting this variable to nil."
-  :package-version '(ERC . "5.6")
+  :package-version '(ERC . "5.6.1")
   :set #'erc-track--massage-nick-button-faces
   :type (erc--with-dependent-type-match
          (repeat (choice face (repeat :tag "Combination" face)))
@@ -636,49 +647,79 @@ keybindings will not do anything useful."
 	       (erc-track-enable))
 	   (set sym val))))
 
+(defvar-local erc-track--priority-faces nil
+  "Local copy of `erc-track-faces-priority-list' as a hash table.
+Keys are faces and values are rank integers (smaller is more important).")
+
 (defvar-local erc-track--normal-faces nil
-  "Local copy of `erc-track-faces-normal-list' as a hash table.")
+  "Local copy of `erc-track-faces-normal-list' as a hash table.
+Keys and values are faces.  The table is weak valued so it can double as
+a buttonizing cache.  See `erc-button-add-button' and `erc--merge-prop'.")
 
 (defun erc-track--setup ()
   "Initialize a buffer for use with the `track' module.
-If this is a server buffer or `erc-track-faces-normal-list' is
-locally bound, create a new `erc-track--normal-faces' for the
-current buffer.  Otherwise, set the local value to the server
-buffer's."
+If this is a server buffer or either `erc-track-faces-normal-list' or
+`erc-track-faces-priority-list' is locally bound, create a new cache
+table with corresponding local variable `erc-track--normal-faces' or
+`erc-track--priority-faces'.  Otherwise, in target buffers with no local
+binding, set the cache variable's local value to that of server's."
   (if erc-track-mode
-      (let ((existing (erc-with-server-buffer erc-track--normal-faces))
-            (localp (and erc--target
-                         (local-variable-p 'erc-track-faces-normal-list)))
-            (opts '(erc-track-faces-normal-list erc-track-faces-priority-list))
-            warnp table)
+      (let (warnp)
         ;; Don't bother warning users who've disabled `button'.
-        (unless (or erc--target (not (or (bound-and-true-p erc-button-mode)
-                                         (memq 'button erc-modules))))
-          (when (or localp (local-variable-p 'erc-track-faces-priority-list))
-            (dolist (opt opts)
+        (unless (or erc--target
+                    (not (or (bound-and-true-p erc-button-mode)
+                             (memq 'button erc-modules))))
+          (dolist (opt '(erc-track-faces-normal-list
+                         erc-track-faces-priority-list))
+            (when (local-variable-p opt)
               (erc-track--massage-nick-button-faces opt (symbol-value opt)
-                                                    #'set)))
-          (dolist (opt opts)
-            (when (get opt 'erc-track--obsolete-faces)
-              (push opt warnp)
+                                                    #'set))
+            (when-let ((migrations (get opt 'erc-track--obsolete-faces))
+                       ((consp migrations)))
+              (push (cons opt
+                          (mapcar (pcase-lambda (`(,old . ,new))
+                                    (format (if new "changed %s to %s"
+                                              "removed %s")
+                                            old new))
+                                  migrations))
+                    warnp)
               (put opt 'erc-track--obsolete-faces nil)))
           (when warnp
-            (erc--warn-once-before-connect 'erc-track-mode
-              (if (cdr warnp) "Options " "Option ")
-              (mapconcat (lambda (o) (format "`%S'" o)) warnp " and ")
-              (if (cdr warnp) " contain" " contains")
-              " an obsolete item, %S, intended to match buttonized nicknames."
-              " ERC has changed it to %S for the current session."
-              " Please save the current value to silence this message."
-              '(erc-nick-default-face erc-default-face)
-              '(erc-button-nick-default-face erc-default-face))))
-        (when (or (null existing) localp)
-          (setq table (map-into (mapcar (lambda (f) (cons f f))
-                                        erc-track-faces-normal-list)
-                                '(hash-table :test equal :weakness value))))
-        (setq erc-track--normal-faces (or table existing))
-        (unless (or localp existing)
-          (erc-with-server-buffer (setq erc-track--normal-faces table))))
+            (pcase-dolist (`(,opt . ,migrations) warnp)
+              (erc--warn-once-before-connect 'erc-track-mode
+                "Option `%S' contains "
+                (if (cdr migrations) "obsolete items." "an obsolete item.")
+                " ERC has done the following for the current session: %s."
+                " Please review these changes and, if convinced,"
+                " silence this message by saving the current value."
+                opt (string-join migrations ", ")))))
+        ;; Set `erc-track--priority-faces' cache to new or shared value.
+        (let* ((localp (and erc--target
+                            (local-variable-p 'erc-track-faces-priority-list)))
+               (existing (erc-with-server-buffer erc-track--priority-faces))
+               (table (or (and (not localp) existing)
+                          (let ((p 0))
+                            (map-into
+                             (mapcar (lambda (f) (cons f (cl-incf p)))
+                                     (append erc-track--attn-faces
+                                             erc-track-faces-priority-list))
+                             `(hash-table :test equal))))))
+          (setq erc-track--priority-faces table)
+          (unless (or localp existing)
+            (erc-with-server-buffer (setq erc-track--priority-faces table))))
+        ;; Likewise for `erc-track--normal-faces' cache.
+        (let* ((localp (and erc--target
+                            (local-variable-p 'erc-track-faces-normal-list)))
+               (existing (erc-with-server-buffer erc-track--normal-faces))
+               (table (or (and (not localp) existing)
+                          (map-into (mapcar (lambda (f) (cons f f))
+                                            erc-track-faces-normal-list)
+                                    `(hash-table :test equal
+                                                 :weakness value)))))
+          (setq erc-track--normal-faces table)
+          (unless (or localp existing)
+            (erc-with-server-buffer (setq erc-track--normal-faces table)))))
+    (kill-local-variable 'erc-track--priority-faces)
     (kill-local-variable 'erc-track--normal-faces)))
 
 ;;; Visibility
@@ -915,44 +956,54 @@ them, it can't be replaced."
 (defvar erc-track--alt-normals-function nil
   "A function to possibly elect a \"normal\" face.
 Called with the current incumbent and the worthiest new contender
-followed by all new contending faces and so-called \"normal\"
-faces.  See `erc-track--select-mode-line-face' for their meanings
-and expected types.  This function should return a face or nil.")
+followed by all new contending faces, ranked faces, and so-called
+\"normal\" faces.  See `erc-track--select-mode-line-face' for their
+meanings and expected types.  This function should return a face or nil.")
 
 (defun erc-track--select-mode-line-face (cur-face new-faces ranks normals)
   "Return CUR-FACE or a replacement for displaying in the mode-line, or nil.
-Expect RANKS to be a list of faces and both NORMALS and the car
-of NEW-FACES to be hash tables mapping faces to non-nil values.
-Assume the latter's makeup and that of RANKS to resemble
-`erc-track-faces-normal-list' and `erc-track-faces-priority-list'.
-If NEW-FACES has a cdr, expect it to be its car's contents
-ordered from most recently seen (later in the buffer) to
-earliest.  In general, act like `erc-track-select-mode-line-face'
-except appeal to `erc-track--alt-normals-function' if it's
-non-nil, falling back on reconsidering NEW-FACES when CUR-FACE
-outranks all its members.  That is, choose the first among RANKS
-in NEW-FACES not equal to CUR-FACE.  Failing that, choose the
-first face in NEW-FACES that's also in NORMALS, assuming
-NEW-FACES has a cdr."
+Expect NEW-FACES to be a cons cell whose car is a hash table mapping
+faces present in the applicable region to t and whose cdr is its car's
+contents ordered from most recently seen (later in the buffer) to
+earliest.  Expect RANKS to be a cons cell whose car is a hash table
+similar to `erc-track--priority-faces' and whose cdr is a list of
+prioritized faces resembling `erc-track-faces-priority-list'.  Expect
+NORMALS to be a hash table mapping faces to themselves.  In general, act
+identically to `erc-track-select-mode-line-face', except appeal to
+`erc-track--alt-normals-function' if it's non-nil, and fall back on
+reconsidering only NEW-FACES appearing in NORMALS when CUR-FACE is
+itself \"normal\" and outranks all NEW-FACES.  That is, choose the first
+among RANKS in both NEW-FACES and NORMALS not equal to CUR-FACE.
+Failing that, choose the first face in both NEW-FACES and NORMALS."
   (cl-check-type erc-track-ignore-normal-contenders-p null)
   (cl-check-type new-faces cons)
+  ;; Choose the highest ranked face in `erc-track-faces-priority-list'
+  ;; that's either `cur-face' itself or one appearing in the region
+  ;; being processed.
   (when-let ((choice (catch 'face
-                       (dolist (candidate ranks)
+                       (dolist (candidate (cdr ranks))
                          (when (or (equal candidate cur-face)
                                    (gethash candidate (car new-faces)))
                            (throw 'face candidate))))))
     (or (and erc-track--alt-normals-function
              (funcall erc-track--alt-normals-function
-                      cur-face choice new-faces normals))
+                      cur-face choice new-faces ranks normals))
+        ;; If `choice' is still `cur-face' and also a "normal", attempt
+        ;; to choose another normal in order to produce the flickering
+        ;; effect mentioned in the doc of `erc-track-faces-normal-list'.
         (and (equal choice cur-face)
              (gethash choice normals)
              (catch 'face
+               ;; If ranked "normal" faces other than `choice' appear in
+               ;; the region, return the most important one.
                (progn
-                 (dolist (candidate ranks)
+                 (dolist (candidate (cdr ranks))
                    (when (and (not (equal candidate choice))
                               (gethash candidate (car new-faces))
                               (gethash choice normals))
                      (throw 'face candidate)))
+                 ;; Otherwise, go with any "normal" face other than
+                 ;; `choice' in the region.
                  (dolist (candidate (cdr new-faces))
                    (when (and (not (equal candidate choice))
                               (gethash candidate normals))
@@ -996,14 +1047,24 @@ the current buffer is in `erc-mode'."
              (normals erc-track--normal-faces)
              (erc-track-faces-priority-list
               `(,@erc-track--attn-faces ,@erc-track-faces-priority-list))
-             (ranks erc-track-faces-priority-list)
+             (ranks (cons erc-track--priority-faces
+                          erc-track-faces-priority-list))
              ((not (and
                     (or (eq erc-track-priority-faces-only 'all)
                         (member this-channel erc-track-priority-faces-only))
-                    (not (catch 'found
-                           (dolist (f ranks)
-                             (when (gethash f (or (car-safe faces) faces))
-                               (throw 'found t)))))))))
+                    ;; Iterate over the shorter of `ranks' and `faces'.
+                    (let* ((r>fp (or erc-track-ignore-normal-contenders-p
+                                     (> (hash-table-count (car ranks))
+                                        (hash-table-count (car faces)))))
+                           (elems (cond ((not r>fp) (cdr ranks)) ; f>=r
+                                        (erc-track-ignore-normal-contenders-p
+                                         faces)
+                                        ((cdr faces))))
+                           (table (if r>fp (car ranks) (car faces))))
+                      (not (catch 'found
+                             (dolist (f elems)
+                               (when (gethash f table)
+                                 (throw 'found t))))))))))
           (progn ; FIXME remove `progn' on next major edit
 	    (if (not (assq (current-buffer) erc-modified-channels-alist))
 		;; Add buffer, faces and counts
@@ -1017,7 +1078,7 @@ the current buffer is in `erc-mode'."
                                         nil faces ranks normals))))
 			    erc-modified-channels-alist))
 	      ;; Else modify the face for the buffer, if necessary.
-	      (when faces
+              (when (or erc-track-ignore-normal-contenders-p (cdr faces))
 		(let* ((cell (assq (current-buffer)
 				   erc-modified-channels-alist))
 		       (old-face (cddr cell))