master 2476abc: Allow provided-mode-derived-p to work on aliases

[Lars Ingebrigtsen]

branch: master
commit 2476abc1f24f1b2385648cfb08cd9f178422497d
Author: Lars Ingebrigtsen <larsi@gnus.org>
Commit: Lars Ingebrigtsen <larsi@gnus.org>

    Allow provided-mode-derived-p to work on aliases
    
    * lisp/subr.el (provided-mode-derived-p): Allow this to work on
    modes that are aliases of other modes (bug#46331).  For instance:
    (provided-mode-derived-p 'javascript-mode 'prog-mode)
---
 lisp/subr.el | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lisp/subr.el b/lisp/subr.el
index 6e52bd2..c1624aa 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -2231,6 +2231,10 @@ Affects only hooks run in the current buffer."
   "Non-nil if MODE is derived from one of MODES or their aliases.
 Uses the `derived-mode-parent' property of the symbol to trace backwards.
 If you just want to check `major-mode', use `derived-mode-p'."
+  ;; If MODE is an alias, then look up the real mode function first.
+  (when-let ((alias (symbol-function mode)))
+    (when (symbolp alias)
+      (setq mode alias)))
   (while
       (and
        (not (memq mode modes))