From 3d02a8e1192a782a16ffdee4940612f69a12629f Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Mon, 18 Apr 2022 13:08:26 -0700
Subject: [PATCH 1/6] Support (encode-time (list s m h D M Y))

* src/timefns.c (Fencode_time): Add support for a 6-elt list arg.
Requested by Max Nikulin for Org (bug#54764).
* test/src/timefns-tests.el (encode-time-alternate-apis): New test.
---
 doc/lispref/os.texi       |  5 +++++
 etc/NEWS                  |  5 +++++
 src/timefns.c             | 21 +++++++++++++++------
 test/src/timefns-tests.el |  9 +++++++++
 4 files changed, 34 insertions(+), 6 deletions(-)

diff --git a/doc/lispref/os.texi b/doc/lispref/os.texi
index cabae08970..bfcd51318e 100644
--- a/doc/lispref/os.texi
+++ b/doc/lispref/os.texi
@@ -1660,6 +1660,11 @@ Time Conversion
 handle situations like this you can use a numeric @var{zone} to
 disambiguate instead.
 
+The first argument can also be a list @code{(@var{second} @var{minute}
+@var{hour} @var{day} @var{month} @var{year})}, which is treated like
+the list @code{(@var{second} @var{minute} @var{hour} @var{day}
+@var{month} @var{year} nil -1 nil)}.
+
 As an obsolescent calling convention, this function can be given six
 or more arguments.  The first six arguments @var{second},
 @var{minute}, @var{hour}, @var{day}, @var{month}, and @var{year}
diff --git a/etc/NEWS b/etc/NEWS
index 3e7788277d..c5a136ea68 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1950,6 +1950,11 @@ For example, '(time-add nil '(1 . 1000))' no longer warns that the
 '(1 . 1000)' acts like '(1000 . 1000000)'.  This warning, which was a
 temporary transition aid for Emacs 27, has served its purpose.
 
++++
+** 'encode-time' now also accepts a 6-element list with just time and date.
+(encode-time (list SECOND MINUTE HOUR DAY MONTH YEAR)) is now short for
+(encode-time (list SECOND MINUTE HOUR DAY MONTH YEAR nil -1 nil)).
+
 +++
 ** 'date-to-time' now assumes earliest values if its argument lacks
 month, day, or time.  For example, (date-to-time "2021-12-04") now
diff --git a/src/timefns.c b/src/timefns.c
index 7a4a7075ed..b0b84a438c 100644
--- a/src/timefns.c
+++ b/src/timefns.c
@@ -1620,6 +1620,9 @@ DEFUN ("encode-time", Fencode_time, Sencode_time, 1, MANY, 0,
 saving time, nil for standard time, and -1 to cause the daylight
 saving flag to be guessed.
 
+TIME can also be a list (SECOND MINUTE HOUR DAY MONTH YEAR), which is
+equivalent to (SECOND MINUTE HOUR DAY MONTH YEAR nil -1 nil).
+
 As an obsolescent calling convention, if this function is called with
 6 or more arguments, the first 6 arguments are SECOND, MINUTE, HOUR,
 DAY, MONTH, and YEAR, and specify the components of a decoded time.
@@ -1645,7 +1648,7 @@ DEFUN ("encode-time", Fencode_time, Sencode_time, 1, MANY, 0,
   if (nargs == 1)
     {
       Lisp_Object tail = a;
-      for (int i = 0; i < 9; i++, tail = XCDR (tail))
+      for (int i = 0; i < 6; i++, tail = XCDR (tail))
 	CHECK_CONS (tail);
       secarg = XCAR (a); a = XCDR (a);
       minarg = XCAR (a); a = XCDR (a);
@@ -1653,11 +1656,17 @@ DEFUN ("encode-time", Fencode_time, Sencode_time, 1, MANY, 0,
       mdayarg = XCAR (a); a = XCDR (a);
       monarg = XCAR (a); a = XCDR (a);
       yeararg = XCAR (a); a = XCDR (a);
-      a = XCDR (a);
-      Lisp_Object dstflag = XCAR (a); a = XCDR (a);
-      zone = XCAR (a);
-      if (SYMBOLP (dstflag) && !FIXNUMP (zone) && !CONSP (zone))
-	tm.tm_isdst = !NILP (dstflag);
+      if (! NILP (a))
+	{
+	  CHECK_CONS (a);
+	  a = XCDR (a);
+	  CHECK_CONS (a);
+	  Lisp_Object dstflag = XCAR (a); a = XCDR (a);
+	  CHECK_CONS (a);
+	  zone = XCAR (a);
+	  if (SYMBOLP (dstflag) && !FIXNUMP (zone) && !CONSP (zone))
+	    tm.tm_isdst = !NILP (dstflag);
+	}
     }
   else if (nargs < 6)
     xsignal2 (Qwrong_number_of_arguments, Qencode_time, make_fixnum (nargs));
diff --git a/test/src/timefns-tests.el b/test/src/timefns-tests.el
index e7c464472d..08d06f27d9 100644
--- a/test/src/timefns-tests.el
+++ b/test/src/timefns-tests.el
@@ -225,6 +225,15 @@ encode-time-dst-numeric-zone
              (encode-time '(29 31 17 30 4 2019 2 t 7200))
              '(23752 27217))))
 
+(ert-deftest encode-time-alternate-apis ()
+  (let* ((time '(30 30 12 15 6 1970))
+	 (time-1 (append time '(nil -1 nil)))
+	 (etime (encode-time time)))
+    (should (time-equal-p etime (encode-time time-1)))
+    (should (time-equal-p etime (apply #'encode-time time)))
+    (should (time-equal-p etime (apply #'encode-time time-1)))
+    (should (time-equal-p etime (apply #'encode-time (append time '(nil)))))))
+
 (ert-deftest float-time-precision ()
   (should (= (float-time '(0 1 0 4025)) 1.000000004025))
   (should (= (float-time '(1000000004025 . 1000000000000)) 1.000000004025))
-- 
2.35.1