bug#5563: zealously reacquiring orphaned erc buffers

[Vivek Dasmohapatra <vivek@etla.org>]

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Tags: patch

This patch should address the case you are seeing - you'll still get
orphaned buffers if you connect to the same server on different ports,
but the patch is trivially extendable to cover that case, should we
decide we care about it.

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diff --git a/lisp/erc/erc.el b/lisp/erc/erc.el
--- a/lisp/erc/erc.el
+++ b/lisp/erc/erc.el
@@ -1566,26 +1566,33 @@ symbol, it may have these values:
 (defun erc-generate-new-buffer-name (server port target &optional proc)
   "Create a new buffer name based on the arguments."
   (when (numberp port) (setq port (number-to-string port)))
-  (let* ((buf-name (or target
-		       (or (let ((name (concat server ":" port)))
-			     (when (> (length name) 1)
-			       name))
-			   ; This fallback should in fact never happen
-			   "*erc-server-buffer*"))))
+  (let ((buf-name (or target
+                      (or (let ((name (concat server ":" port)))
+                            (when (> (length name) 1)
+                              name))
+                          ;; This fallback should in fact never happen
+                          "*erc-server-buffer*")))
+        buffer-name)
     ;; Reuse existing buffers, but not if the buffer is a connected server
     ;; buffer and not if its associated with a different server than the
     ;; current ERC buffer.
-    (if (and erc-reuse-buffers
-	     (get-buffer buf-name)
-	     (or target
-		 (with-current-buffer (get-buffer buf-name)
-		   (and (erc-server-buffer-p)
-			(not (erc-server-process-alive)))))
-	     (with-current-buffer (get-buffer buf-name)
-	       (and (string= erc-session-server server)
-		    (erc-port-equal erc-session-port port))))
-	buf-name
-      (generate-new-buffer-name buf-name))))
+    ;; if buf-name is taken by a different connection (or by something !erc)
+    ;; then see if "buf-name/server" meets the same criteria
+    (dolist (candidate (list buf-name (concat buf-name "/" server))) 
+      (if (and (not buffer-name)
+               erc-reuse-buffers
+               (get-buffer candidate)
+               (or target
+                   (with-current-buffer (get-buffer candidate)
+                     (and (erc-server-buffer-p)
+                          (not (erc-server-process-alive)))))
+               (with-current-buffer (get-buffer candidate)
+                 (and (string= erc-session-server server)
+                      (erc-port-equal erc-session-port port))))
+          (setq buffer-name candidate)))
+    ;; if buffer-name is unset, neither candidate worked out for us,
+    ;; fallback to the old <N> uniquification method:
+    (or buffer-name (generate-new-buffer-name buf-name)) ))
 
 (defun erc-get-buffer-create (server port target &optional proc)
   "Create a new buffer based on the arguments."