(derived-mode-p): Take MODES as a single argument

Looking at uses of `derived-mode-p` and `provide-mode-derived-p`,
I can't find a single use case where it wouldn't be preferable for
it to take a single argument instead of `&rest`: all the calls are
either passing a single argument anyway, or passing a fixed list of modes.
The use of `&rest` just makes the code less efficient and sometimes
more clunky (because of the need for `apply`).
So let's change that (while preserving backward compatibility, of course).

* doc/lispref/modes.texi (Derived Modes): Adjust accordingly.

* lisp/subr.el (provided-mode-derived-p, derived-mode-p): Take the
`modes` as a single argument.

3 files changed, 36 insertions, 12 deletions

diff --git a/doc/lispref/modes.texi b/doc/lispref/modes.texi
index 8670807cbdf..13090a13d71 100644
--- a/doc/lispref/modes.texi
+++ b/doc/lispref/modes.texi
@@ -932,9 +932,14 @@ Do not write an @code{interactive} spec in the definition;
 @code{define-derived-mode} does that automatically.
 @end defmac
 
-@defun derived-mode-p &rest modes
+@defun derived-mode-p modes
 This function returns non-@code{nil} if the current major mode is
-derived from any of the major modes given by the symbols @var{modes}.
+derived from any of the major modes given by the list of symbols
+in @var{modes}.
+Instead of a list, @var{modes} can also be a single mode symbol.
+
+Furthermore, we still support a deprecated calling convention where the
+@var{modes} were passed as separate arguments.
 @end defun
 
 The graph of major modes is accessed with the following lower-level
diff --git a/etc/NEWS b/etc/NEWS
index 8794239c148..c0f76ed052b 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1228,8 +1228,15 @@ values.
 Mostly used internally to do a kind of topological sort of
 inheritance hierarchies.
 
-** New API to control the graph of major modes.
-While 'define-derived-mode' still only support single inheritance,
+** New API for 'derived-mode-p' and control of the graph of major modes.
+
+*** 'derived-mode-p' now takes the list of modes as a single argument.
+The same holds for `provided-mode-derived-p`.
+The old calling convention where multiple modes are passed as
+separate arguments is deprecated.
+
+*** New functions to access the graph of major modes.
+While 'define-derived-mode' still only supports single inheritance,
 modes can declare additional parents (for tests like 'derived-mode-p')
 with `derived-mode-add-parents`.
 Accessing the 'derived-mode-parent' property directly is now
diff --git a/lisp/subr.el b/lisp/subr.el
index dcf49509177..304b71e6168 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -2782,19 +2782,31 @@ The returned list is not fresh, don't modify it.
             (cons mode (remq mode all-parents))
           (put mode 'derived-mode--all-parents (cons mode all-parents))))))))
 
-(defun provided-mode-derived-p (mode &rest modes)
-  "Non-nil if MODE is derived from one of MODES.
-If you just want to check `major-mode', use `derived-mode-p'."
-  (declare (side-effect-free t))
+(defun provided-mode-derived-p (mode &optional modes &rest old-modes)
+  "Non-nil if MODE is derived from a mode that is a member of the list MODES.
+MODES can also be a single mode instead of a list.
+If you just want to check `major-mode', use `derived-mode-p'.
+We also still support the deprecated calling convention:
+\(provided-mode-derived-p MODE &rest MODES)."
+  (declare (side-effect-free t)
+           (advertised-calling-convention (mode modes) "30.1"))
+  (cond
+   (old-modes (setq modes (cons modes old-modes)))
+   ((not (listp modes)) (setq modes (list modes))))
   (let ((ps (derived-mode-all-parents mode)))
     (while (and modes (not (memq (car modes) ps)))
       (setq modes (cdr modes)))
     (car modes)))
 
-(defun derived-mode-p (&rest modes)
-  "Non-nil if the current major mode is derived from one of MODES."
-  (declare (side-effect-free t))
-  (apply #'provided-mode-derived-p major-mode modes))
+(defun derived-mode-p (&optional modes &rest old-modes)
+ "Non-nil if the current major mode is derived from one of MODES.
+MODES should be a list of symbols or a single mode symbol instead of a list.
+We also still support the deprecated calling convention:
+\(derived-mode-p &rest MODES)."
+ (declare (side-effect-free t)
+          (advertised-calling-convention (modes) "30.1"))
+ (provided-mode-derived-p major-mode (if old-modes (cons modes old-modes)
+                                       modes)))
 
 (defun derived-mode-set-parent (mode parent)
   "Declare PARENT to be the parent of MODE."