Bury new ERC buffers by default

* lisp/erc/erc.el (erc-join-buffer): Change default value to `bury'.
(erc-setup-buffer): Make `window-noselect' behave more like its
description and abstain from ever replacing the current buffer.
* test/lisp/erc/erc-scenarios-base-reconnect.el
(erc-scenarios-common-base-reconnect-options): Update helper to handle
new default value for option `erc-join-buffer'.
(erc-scenarios-base-reconnect-options--buffer): Update and rename
function `erc-scenarios-base-reconnect-options--default'.
(erc-scenarios-base-reconnect-options--default): Update and rename
function `erc-scenarios-base-reconnect-options--bury'.
* etc/ERC-NEWS: Update existing display-buffers section for 5.5.
(Bug#51753)

etc/ERC-NEWS

@@ -59,9 +59,17 @@ which, when present, becomes the first argument passed to the "USER"
 IRC command.  The traditional way of setting this globally, via
 'erc-email-userid', is still honored.
 
-** Additional display options for updated buffers.
-Additional flexibility is now available for controlling the behavior
-of newly created target buffers, especially during reconnection.
+** Changes to display options for new ERC buffers.
+The default value for the option 'erc-join-buffer', which determines
+how new buffers are displayed, has been changed to 'bury' for security
+reasons.  Although the old value of 'buffer' is still accessible,
+along with its original behavior, users wanting a safer alternative
+can now opt for an improved 'window-noselect' instead.  It still
+offers the same pronounced visual cue when connecting and joining but
+now avoids any hijacking of the active window as well.
+
+Beyond this, additional flexibility is now available for controlling
+the behavior of newly created target buffers during reconnection.
 
 ** Improved handling of multiline prompt input.
 This means better detection and handling of intervening and trailing

lisp/erc/erc.el

@@ -1651,7 +1651,7 @@ Defaults to the server buffer."
   "IRC port to use for encrypted connections if it cannot be \
 detected otherwise.")
 
-(defcustom erc-join-buffer 'buffer
+(defcustom erc-join-buffer 'bury
   "Determines how to display a newly created IRC buffer.
 
 The available choices are:
@@ -1662,6 +1662,7 @@ The available choices are:
   `bury'            - bury it in a new buffer,
   `buffer'          - in place of the current buffer,
   any other value  - in place of the current buffer."
+  :package-version '(ERC . "5.4.1") ; FIXME increment upon publishing to ELPA
   :group 'erc-buffers
   :type '(choice (const :tag "Split window and select" window)
                  (const :tag "Split window, don't select" window-noselect)
@@ -2148,7 +2149,7 @@ removed from the list will be disabled."
          (display-buffer buffer)
        (switch-to-buffer-other-window buffer)))
     ('window-noselect
-     (display-buffer buffer))
+     (display-buffer buffer '(nil (inhibit-same-window . t))))
     ('bury
      nil)
     ('frame

test/lisp/erc/erc-scenarios-base-reconnect.el

@@ -99,10 +99,11 @@
 
     (funcall test)
 
+    ;; A manual /JOIN command tells ERC we're done auto-reconnecting
     (with-current-buffer "FooNet" (erc-cmd-JOIN "#spam"))
 
-    (erc-d-t-wait-for 5 "Channel #spam shown when autojoined"
-      (eq (window-buffer) (get-buffer "#spam")))
+    (erc-d-t-ensure-for 1 "Newly joined chan ignores `erc-reconnect-display'"
+      (not (eq (window-buffer) (get-buffer "#spam"))))
 
     (ert-info ("Wait for auto reconnect")
       (with-current-buffer erc-server-buffer
@@ -114,43 +115,43 @@
       (with-current-buffer (erc-d-t-wait-for 10 (get-buffer "#spam"))
         (funcall expect 10 "her elves come here anon")))))
 
-(ert-deftest erc-scenarios-base-reconnect-options--default ()
+(ert-deftest erc-scenarios-base-reconnect-options--buffer ()
   :tags '(:expensive-test)
-  (should (eq erc-join-buffer 'buffer))
+  (should (eq erc-join-buffer 'bury))
   (should-not erc-reconnect-display)
 
   ;; FooNet (the server buffer) is not switched to because it's
   ;; already current (but not shown) when `erc-open' is called.  See
   ;; related conditional guard towards the end of that function.
 
-  (erc-scenarios-common--base-reconnect-options
-   (lambda ()
-     (pop-to-buffer-same-window "*Messages*")
-
-     (erc-d-t-ensure-for 1 "Server buffer not shown"
-       (not (eq (window-buffer) (get-buffer "FooNet"))))
-
-     (erc-d-t-wait-for 5 "Channel #chan shown when autojoined"
-       (eq (window-buffer) (get-buffer "#chan"))))))
-
-(ert-deftest erc-scenarios-base-reconnect-options--bury ()
-  :tags '(:expensive-test)
-  (should (eq erc-join-buffer 'buffer))
-  (should-not erc-reconnect-display)
-
-  (let ((erc-reconnect-display 'bury))
+  (let ((erc-reconnect-display 'buffer))
     (erc-scenarios-common--base-reconnect-options
-
      (lambda ()
        (pop-to-buffer-same-window "*Messages*")
 
        (erc-d-t-ensure-for 1 "Server buffer not shown"
          (not (eq (window-buffer) (get-buffer "FooNet"))))
 
-       (erc-d-t-ensure-for 3 "Channel #chan not shown"
-         (not (eq (window-buffer) (get-buffer "#chan"))))
+       (erc-d-t-wait-for 5 "Channel #chan shown when autojoined"
+         (eq (window-buffer) (get-buffer "#chan")))))))
 
-       (eq (window-buffer) (messages-buffer))))))
+(ert-deftest erc-scenarios-base-reconnect-options--default ()
+  :tags '(:expensive-test)
+  (should (eq erc-join-buffer 'bury))
+  (should-not erc-reconnect-display)
+
+  (erc-scenarios-common--base-reconnect-options
+
+   (lambda ()
+     (pop-to-buffer-same-window "*Messages*")
+
+     (erc-d-t-ensure-for 1 "Server buffer not shown"
+       (not (eq (window-buffer) (get-buffer "FooNet"))))
+
+     (erc-d-t-ensure-for 3 "Channel #chan not shown"
+       (not (eq (window-buffer) (get-buffer "#chan"))))
+
+     (eq (window-buffer) (messages-buffer)))))
 
 ;; Upon reconnecting, playback for channel and target buffers is
 ;; routed correctly.  Autojoin is irrelevant here, but for the