buffer-match-p: Resolve backward compat concerns

* doc/lispref/buffers.texi (Buffer List): Document 'major-mode'
and 'derived-mode' predicates.  Fix some typos.

* lisp/subr.el (buffer-match-p): Use the structure initially
pioneered by project-kill-buffer-conditions as-is (bug#54296).

* lisp/progmodes/project.el (project-kill-buffer-conditions)
(project--buffer-check): Revert the latest change.
(project--buffer-check): Add support for lambda predicates.

1 files changed, 9 insertions, 3 deletions

diff --git a/lisp/subr.el b/lisp/subr.el
index 50ae357a136..c1c9759b03d 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -6855,9 +6855,11 @@ CONDITION is either:
   arguments, and returns non-nil if the buffer matches,
 - a cons-cell, where the car describes how to interpret the cdr.
   The car can be one of the following:
-  * `major-mode': the buffer matches if the buffer's major
-    mode is derived from the major mode denoted by the cons-cell's
-    cdr
+  * `derived-mode': the buffer matches if the buffer's major mode
+    is derived from the major mode in the cons-cell's cdr.
+  * `major-mode': the buffer matches if the buffer's major mode
+    is eq to the cons-cell's cdr.  Prefer using `derived-mode'
+    instead when both can work.
   * `not': the cdr is interpreted as a negation of a condition.
   * `and': the cdr is a list of recursive conditions, that all have
     to be met.
@@ -6877,6 +6879,10 @@ CONDITION is either:
                           (funcall condition buffer)
                         (funcall condition buffer arg)))
                      ((eq (car-safe condition) 'major-mode)
+                      (eq
+                       (buffer-local-value 'major-mode buffer)
+                       (cdr condition)))
+                     ((eq (car-safe condition) 'derived-mode)
                       (provided-mode-derived-p
                        (buffer-local-value 'major-mode buffer)
                        (cdr condition)))