New command 'project-list-buffers' bound to 'C-x p C-b' (bug#59153)

* doc/emacs/maintaining.texi (Project Buffer Commands):
Add 'project-list-buffers'.

* lisp/buff-menu.el (Buffer-menu-filter-predicate): New defvar-local.
(list-buffers-noselect): Add new optional arg 'filter-predicate'.
Set 'Buffer-menu-filter-predicate' to 'filter-predicate'.
(list-buffers--refresh): Use 'Buffer-menu-filter-predicate'.

* lisp/progmodes/project.el (project-prefix-map): Bind "\C-b" to
'project-list-buffers'.
(project-list-buffers): New command.

doc/emacs/maintaining.texi

@@ -1832,6 +1832,8 @@ directory.  @xref{Top,Eshell,Eshell, eshell, Eshell: The Emacs Shell}.
 @item C-x p b
 Switch to another buffer belonging to the current project
 (@code{project-switch-to-buffer}).
+@item C-x p C-b
+List the project buffers (@code{project-list-buffers}).
 @item C-x p k
 Kill all live buffers that belong to the current project
 (@code{project-kill-buffers}).
@@ -1847,6 +1849,11 @@ switch between buffers that belong to the current project by prompting
 for a buffer to switch and considering only the current project's
 buffers as candidates for completion.
 
+@findex project-list-buffers
+  Like the command @code{list-buffers} (@pxref{List Buffers}), the
+command @kbd{C-x p C-b} (@code{project-list-buffers}) displays a list
+of existing buffers, but only belonging to the current project.
+
 @findex project-kill-buffers
 @vindex project-kill-buffer-conditions
 @vindex project-kill-buffers-display-buffer-list

etc/NEWS

@@ -2212,6 +2212,10 @@ it with new 'term-{faint,italic,slow-blink,fast-blink}' faces.
 *** 'project-find-file' and 'project-or-external-find-file' now accept
 a prefix argument which is interpreted to mean "include all files".
 
++++
+*** New command 'project-list-buffers' bound to 'C-x p C-b'.
+This command displays a list of buffers from the current project.
+
 +++
 *** 'project-kill-buffers' can display the list of buffers to kill.
 Customize the user option 'project-kill-buffers-display-buffer-list'

lisp/buff-menu.el

@@ -100,6 +100,13 @@ as it is by default."
 This is set by the prefix argument to `buffer-menu' and related
 commands.")
 
+(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.
+The value should be a function of one argument; it will be
+called with the buffer.  If this function returns non-nil,
+then the buffer will be displayed in the buffer list.")
+
 (defvar-keymap Buffer-menu-mode-map
   :doc "Local keymap for `Buffer-menu-mode' buffers."
   :parent tabulated-list-mode-map
@@ -616,19 +623,23 @@ This behaves like invoking \\[read-only-mode] in that buffer."
 ;;; Functions for populating the Buffer Menu.
 
 ;;;###autoload
-(defun list-buffers-noselect (&optional files-only buffer-list)
+(defun list-buffers-noselect (&optional files-only buffer-list filter-predicate)
   "Create and return a Buffer Menu buffer.
 This is called by `buffer-menu' and others as a subroutine.
 
 If FILES-ONLY is non-nil, show only file-visiting buffers.
 If BUFFER-LIST is non-nil, it should be a list of buffers; it
-means list those buffers and no others."
+means list those buffers and no others.
+If FILTER-PREDICATE is non-nil, it should be a function
+that filters out buffers from the list of buffers.
+See more at `Buffer-menu-filter-predicate'."
   (let ((old-buffer (current-buffer))
 	(buffer (get-buffer-create "*Buffer List*")))
     (with-current-buffer buffer
       (Buffer-menu-mode)
       (setq Buffer-menu-files-only
 	    (and files-only (>= (prefix-numeric-value files-only) 0)))
+      (setq Buffer-menu-filter-predicate filter-predicate)
       (list-buffers--refresh buffer-list old-buffer)
       (tabulated-list-print))
     buffer))
@@ -650,6 +661,8 @@ means list those buffers and no others."
         (marked-buffers (Buffer-menu-marked-buffers))
         (buffer-menu-buffer (current-buffer))
 	(show-non-file (not Buffer-menu-files-only))
+	(filter-predicate (and (functionp Buffer-menu-filter-predicate)
+			       Buffer-menu-filter-predicate))
 	entries name-width)
     ;; Collect info for each buffer we're interested in.
     (dolist (buffer (or buffer-list
@@ -663,7 +676,9 @@ means list those buffers and no others."
 			 (and (or (not (string= (substring name 0 1) " "))
                                   file)
 			      (not (eq buffer buffer-menu-buffer))
-			      (or file show-non-file))))
+			      (or file show-non-file)
+			      (or (not filter-predicate)
+				  (funcall filter-predicate buffer)))))
 	    (push (list buffer
 			(vector (cond
                                  ((eq buffer old-buffer) ".")

lisp/progmodes/project.el

@@ -712,6 +712,7 @@ DIRS must contain directory names."
     (define-key map "G" 'project-or-external-find-regexp)
     (define-key map "r" 'project-query-replace-regexp)
     (define-key map "x" 'project-execute-extended-command)
+    (define-key map "\C-b" 'project-list-buffers)
     map)
   "Keymap for project commands.")
 
@@ -1222,6 +1223,28 @@ displayed."
   (interactive (list (project--read-project-buffer)))
   (display-buffer-other-frame buffer-or-name))
 
+;;;###autoload
+(defun project-list-buffers (&optional arg)
+  "Display a list of project buffers.
+The list is displayed in a buffer named \"*Buffer List*\".
+
+By default, all project buffers are listed except those whose names
+start with a space (which are for internal use).  With prefix argument
+ARG, show only buffers that are visiting files."
+  (interactive "P")
+  (let ((pr (project-current t)))
+    (display-buffer
+     (if (version< emacs-version "29.0.50")
+         (let ((buf (list-buffers-noselect arg (project-buffers pr))))
+           (with-current-buffer buf
+             (setq-local revert-buffer-function
+                         (lambda (&rest _ignored)
+                           (list-buffers--refresh (project-buffers pr))
+                           (tabulated-list-print t))))
+           buf)
+       (list-buffers-noselect
+        arg nil (lambda (buf) (memq buf (project-buffers pr))))))))
+
 (defcustom project-kill-buffer-conditions
   '(buffer-file-name    ; All file-visiting buffers are included.
     ;; Most of temp and logging buffers (aside from hidden ones):