Add tabulated-list-groups and Buffer-menu-group-by (bug#69305)

* doc/lispref/modes.texi (Tabulated List Mode):
Add defvar tabulated-list-groups.

* lisp/buff-menu.el (Buffer-menu-group-by): New defcustom.
(Buffer-menu-unmark-all-buffers): Use tabulated-list-get-entry
to check whether the current line contains an entry.
(list-buffers-noselect): Enable outline-minor-mode
for tabulated-list-groups.
(list-buffers--refresh): When Buffer-menu-group-by is non-nil,
set tabulated-list-groups.
(Buffer-menu-group-by-mode, Buffer-menu-group-by-root):
New functions.

* lisp/emacs-lisp/tabulated-list.el (tabulated-list-groups):
New buffer-local variable.
(tabulated-list-print-fake-header): Add distinct overlay
property 'fake-header'.
(tabulated-list-header-overlay-p): Filter out overlays that
don't have the property 'fake-header'.
(tabulated-list-print): Use the variable 'tabulated-list-groups'
to sort entries in groups separately.
(tabulated-list-print-entries): New function factored out from
'tabulated-list-print'.

* test/lisp/emacs-lisp/tabulated-list-tests.el (tabulated-list-groups):
New test.

1 files changed, 41 insertions, 0 deletions

diff --git a/test/lisp/emacs-lisp/tabulated-list-tests.el b/test/lisp/emacs-lisp/tabulated-list-tests.el
index 8be2be3139e..e53268b3f14 100644
--- a/test/lisp/emacs-lisp/tabulated-list-tests.el
+++ b/test/lisp/emacs-lisp/tabulated-list-tests.el
@@ -130,4 +130,45 @@
    (should-error (tabulated-list-sort) :type 'user-error)
    (should-error (tabulated-list-sort 4) :type 'user-error)))
 
+(ert-deftest tabulated-list-groups ()
+  (with-temp-buffer
+    (tabulated-list-mode)
+    (setq tabulated-list-groups
+          (reverse
+           (seq-group-by (lambda (b) (concat "* " (aref (cadr b) 3)))
+                         tabulated-list--test-entries)))
+    (setq tabulated-list-format tabulated-list--test-format)
+    (setq tabulated-list-padding 7)
+    (tabulated-list-init-header)
+    (tabulated-list-print)
+    ;; Basic printing.
+    (should (string-equal
+             (buffer-substring-no-properties (point-min) (point-max))
+             "\
+* installed
+       zzzz-game  zzzz-game  2113      installed   play zzzz in Emacs
+       mode       mode       1128      installed   A simple mode for editing Actionscript 3 files
+* available
+       abc-mode   abc-mode   944       available   Major mode for editing abc music files
+* obsolete
+       4clojure   4clojure   1507      obsolete    Open and evaluate 4clojure.com questions
+"))
+    ;; Sort and preserve position.
+    (forward-line 2)
+    (let ((pos (thing-at-point 'line)))
+      (tabulated-list-next-column 2)
+      (tabulated-list-sort)
+      (should (equal (thing-at-point 'line) pos))
+      (should (string-equal
+               (buffer-substring-no-properties (point-min) (point-max))
+               "\
+* installed
+       mode       mode       1128      installed   A simple mode for editing Actionscript 3 files
+       zzzz-game  zzzz-game  2113      installed   play zzzz in Emacs
+* available
+       abc-mode   abc-mode   944       available   Major mode for editing abc music files
+* obsolete
+       4clojure   4clojure   1507      obsolete    Open and evaluate 4clojure.com questions
+")))))
+
 ;;; tabulated-list-tests.el ends here