Optionally show internal buffers in Buffer Menu mode

Internal buffers were never shown before but they can be of interest
to Elisp developers, especially since there is no general mechanism to
remove unused buffers.

* lisp/buff-menu.el (Buffer-menu-show-internal)
(Buffer-menu--selection-message, Buffer-menu-toggle-internal): New.
(Buffer-menu-mode-map): Bind to `I`.
(Buffer-menu-mode-menu): Add menu entry.
(list-buffers--refresh): Extend filtering logic.
* etc/NEWS: Announce.

(cherry picked from commit f6225d125c07bbde8c828b40eb6e81333e051c2a)

diff --git a/etc/NEWS b/etc/NEWS
index 4b0bfa1c15ce7f37f30898173d971cbb4a2bcb52..b429419f7c8c06d016477052139561e5618466f5 100644 (file)
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1414,6 +1414,12 @@ This user option lets you customize the sample text that
 "*Completions*" buffer.  By default this is set to the string
 "SAMPLE", which retains compatibility with Emacs 29.
 
+---
+*** New command 'Buffer-menu-toggle-internal', locally bound to 'I'.
+This command toggles the display of internal buffers in Buffer Menu mode;
+that is, buffers not visiting a file and whose names start with a space.
+Previously, such buffers were never shown.
+
 ** Customize
 
 +++

diff --git a/lisp/buff-menu.el b/lisp/buff-menu.el
index 5796544c5342ca29f63b9857bc6b35b400214630..9561141f0c3cc520a3e608f6a8f8e19a6d241bee 100644 (file)
--- a/lisp/buff-menu.el
+++ b/lisp/buff-menu.el
@@ -100,6 +100,10 @@ as it is by default."
 This is set by the prefix argument to `buffer-menu' and related
 commands.")
 
+(defvar-local Buffer-menu-show-internal nil
+  "Non-nil if the current Buffer Menu lists internal buffers.
+Internal buffers are those whose names start with a space.")
+
 (defvar-local Buffer-menu-filter-predicate nil
   "Function to filter out buffers in the buffer list.
 Buffers that don't satisfy the predicate will be skipped.
@@ -140,6 +144,7 @@ then the buffer will be displayed in the buffer list.")
   "V"           #'Buffer-menu-view
   "O"           #'Buffer-menu-view-other-window
   "T"           #'Buffer-menu-toggle-files-only
+  "I"           #'Buffer-menu-toggle-internal
   "M-s a C-s"   #'Buffer-menu-isearch-buffers
   "M-s a C-M-s" #'Buffer-menu-isearch-buffers-regexp
   "M-s a C-o"   #'Buffer-menu-multi-occur
@@ -197,6 +202,10 @@ then the buffer will be displayed in the buffer list.")
      :help "Toggle whether the current buffer-menu displays only file buffers"
      :style toggle
      :selected Buffer-menu-files-only]
+    ["Show Internal Buffers" Buffer-menu-toggle-internal
+     :help "Toggle whether the current buffer-menu displays internal buffers"
+     :style toggle
+     :selected Buffer-menu-show-internal]
     "---"
     ["Refresh" revert-buffer
      :help "Refresh the *Buffer List* buffer contents"]
@@ -317,6 +326,11 @@ ARG, show only buffers that are visiting files."
   (interactive "P")
   (display-buffer (list-buffers-noselect arg)))
 
+(defun Buffer-menu--selection-message ()
+  (message (cond (Buffer-menu-files-only "Showing only file-visiting buffers.")
+                 (Buffer-menu-show-internal "Showing all buffers.")
+                (t "Showing all non-internal buffers."))))
+
 (defun Buffer-menu-toggle-files-only (arg)
   "Toggle whether the current `buffer-menu' displays only file buffers.
 With a positive ARG, display only file buffers.  With zero or
@@ -325,9 +339,18 @@ negative ARG, display other buffers as well."
   (setq Buffer-menu-files-only
        (cond ((not arg) (not Buffer-menu-files-only))
              ((> (prefix-numeric-value arg) 0) t)))
-  (message (if Buffer-menu-files-only
-              "Showing only file-visiting buffers."
-            "Showing all non-internal buffers."))
+  (Buffer-menu--selection-message)
+  (revert-buffer))
+
+(defun Buffer-menu-toggle-internal (arg)
+  "Toggle whether the current `buffer-menu' displays internal buffers.
+With a positive ARG, display non-internal buffers only.  With zero or
+negative ARG, display internal buffers as well."
+  (interactive "P" Buffer-menu-mode)
+  (setq Buffer-menu-show-internal
+       (cond ((not arg) (not Buffer-menu-show-internal))
+             ((> (prefix-numeric-value arg) 0) t)))
+  (Buffer-menu--selection-message)
   (revert-buffer))
 
 (define-obsolete-function-alias 'Buffer-menu-sort 'tabulated-list-sort
@@ -667,6 +690,7 @@ See more at `Buffer-menu-filter-predicate'."
         (marked-buffers (Buffer-menu-marked-buffers))
         (buffer-menu-buffer (current-buffer))
        (show-non-file (not Buffer-menu-files-only))
+        (show-internal Buffer-menu-show-internal)
        (filter-predicate (and (functionp Buffer-menu-filter-predicate)
                               Buffer-menu-filter-predicate))
        entries name-width)
@@ -686,7 +710,8 @@ See more at `Buffer-menu-filter-predicate'."
               (file buffer-file-name))
          (when (and (buffer-live-p buffer)
                     (or buffer-list
-                        (and (or (not (string= (substring name 0 1) " "))
+                        (and (or show-internal
+                                  (not (string= (substring name 0 1) " "))
                                   file)
                              (not (eq buffer buffer-menu-buffer))
                              (or file show-non-file)