From 7155fbd9f4afe9c9fd9dd2c89e28830a9d6612d7 Mon Sep 17 00:00:00 2001
From: "F. Jason Park" <jp@neverwas.me>
Date: Mon, 23 May 2022 00:15:18 -0700
Subject: [PATCH 0/1] *** NOT A PATCH ***

*** BLURB HERE ***

F. Jason Park (1):
  Allow erc-reuse-frames to favor connections

 lisp/erc/erc.el            |  52 +++++++++++++---
 test/lisp/erc/erc-tests.el | 119 +++++++++++++++++++++++++++++++++++++
 2 files changed, 163 insertions(+), 8 deletions(-)

Interdiff:
diff --git a/lisp/erc/erc.el b/lisp/erc/erc.el
index f82fb07a66..13ac0ec979 100644
--- a/lisp/erc/erc.el
+++ b/lisp/erc/erc.el
@@ -1538,11 +1538,12 @@ erc-frame-dedicated-flag
 (defcustom erc-reuse-frames t
   "Non-nil means only create a frame for undisplayed buffers.
 For new target buffers, a value of 'displayed' extends this to mean use
-the frame of any buffer from the same server connection, visible or not.
-When this option is nil, a new frame is always created.  Regardless of
-its value, this option is ignored unless `erc-join-buffer' is set to
-`frame'.  Note that like most options in the `erc-buffer' customize
-group, this has no effect on server buffers while reconnecting."
+the frame of any buffer from the same server connection, visible or not,
+or, as a last resort, a frame showing any ERC buffer.  When this option
+is nil, a new frame is always created.  Regardless of its value, this
+option is ignored unless `erc-join-buffer' is set to `frame'.  Note that
+like most options in the `erc-buffer' customize group, this has no
+effect on server buffers while reconnecting."
   :package-version '(ERC . "5.4.1") ; FIXME update when publishing to ELPA
   :group 'erc-buffers
   :type '(choice boolean
@@ -1948,18 +1949,30 @@ erc-update-modules
             (funcall sym 1)
           (error "`%s' is not a known ERC module" mod))))))
 
-(defun erc--setup-buffer-frame-displayed (buffer)
+(defun erc--setup-buffer-first-win (frame a b)
+  (catch 'found
+    (walk-window-tree
+     (lambda (w)
+       (when (eq (buffer-local-value a (window-buffer w)) b)
+         (throw 'found t)))
+     frame nil 0)))
+
+(defun erc--display-buffer-use-some-frame (buffer alist)
   "Maybe display BUFFER in an existing frame for the same connection.
-If performed, return window used; otherwise, return nil."
+If performed, return window used; otherwise, return nil.  Forward ALIST
+to display-buffer machinery."
   (when-let*
-      ((bs (erc-buffer-list nil erc-server-process))
-       (visit (lambda (w) (when (memq (window-buffer w) bs) (throw 'found t))))
-       (test (lambda (fr) (catch 'found (walk-windows visit 0 fr))))
-       ((or (cdr (frame-list)) (funcall test (selected-frame)))))
-    (display-buffer buffer `((display-buffer-use-some-frame)
-                             (inhibit-switch-frame . t)
-                             (inhibit-same-window . t)
-                             (frame-predicate . ,test)))))
+      ((same-proc-p (lambda (fr)
+                      (erc--setup-buffer-first-win fr 'erc-server-process
+                                                   erc-server-process)))
+       (same-mode-p (lambda (fr)
+                      (erc--setup-buffer-first-win fr 'major-mode 'erc-mode)))
+       ((or (cdr (frame-list)) (funcall same-mode-p (selected-frame))))
+       (frame (car (or (filtered-frame-list same-proc-p)
+                       (filtered-frame-list same-mode-p))))
+       (window (get-lru-window frame nil t)))
+    ;; FIXME don't rely on internal window.el function (tab-bar also does it)
+    (window--display-buffer buffer window 'reuse alist)))
 
 (defun erc-setup-buffer (buffer)
   "Consults `erc-join-buffer' to find out how to display `BUFFER'."
@@ -1975,9 +1988,9 @@ erc-setup-buffer
     ('frame
      (cond
       ((and (eq erc-reuse-frames 'displayed)
-            erc-default-recipients ; change this to `erc--target' after bug#48598
-            (not (get-buffer-window buffer t))
-            (erc--setup-buffer-frame-displayed buffer)))
+            (not (get-buffer-window buffer t)))
+       (display-buffer buffer `((erc--display-buffer-use-some-frame)
+                                (inhibit-same-window . t))))
       ((or (not erc-reuse-frames)
            (not (get-buffer-window buffer t)))
        (let ((frame (make-frame (or erc-frame-alist
diff --git a/test/lisp/erc/erc-tests.el b/test/lisp/erc/erc-tests.el
index 1eac6b22c9..686db3bb2e 100644
--- a/test/lisp/erc/erc-tests.el
+++ b/test/lisp/erc/erc-tests.el
@@ -173,6 +173,10 @@ erc--switch-to-buffer
 
 (ert-deftest erc-reuse-frames ()
   ;; TODO run this in a pseudo terminal subprocess for EMBA
+  ;;
+  ;; TODO case that simulates automatic reconnecting, with an
+  ;; existing, unselected frame containing two windows, one with a
+  ;; dead ERC buffer and the other a non-ERC buffer
   (skip-unless (not noninteractive))
   (should-not erc-frame-dedicated-flag)
   (let ((erc-join-buffer 'frame)
-- 
2.36.1