master b40009e2f9 2/3: ISO 8601 strings sans "Z" don’t specify DST flag

[Paul Eggert]

branch: master
commit b40009e2f933c1c1e1c55ac7474df2797e4c7e17
Author: Paul Eggert <eggert@cs.ucla.edu>
Commit: Paul Eggert <eggert@cs.ucla.edu>

    ISO 8601 strings sans "Z" don’t specify DST flag
    
    * lisp/calendar/iso8601.el (iso8601--zone-dst): New function.
    (iso8601-parse, iso8601-parse-time): Use it.
    (iso8601--decoded-time): Default dst to -1, not nil.
    * test/lisp/calendar/iso8601-tests.el (test-iso8601-combined)
    (standard-test-time-of-day-zone): Adjust to new behavior.
---
 lisp/calendar/iso8601.el            | 12 +++++++++---
 test/lisp/calendar/iso8601-tests.el | 20 ++++++++++----------
 2 files changed, 19 insertions(+), 13 deletions(-)

diff --git a/lisp/calendar/iso8601.el b/lisp/calendar/iso8601.el
index e31120f52f..6827a957a6 100644
--- a/lisp/calendar/iso8601.el
+++ b/lisp/calendar/iso8601.el
@@ -114,6 +114,11 @@
          iso8601--duration-week-match
          iso8601--duration-combined-match)))
 
+;; "Z" dnd "z" are standard time; nil and [-+][0-9][0-9]... are local time
+;; with unknown DST.
+(defun iso8601--zone-dst (zone)
+  (if (= (length zone) 1) nil -1))
+
 (defun iso8601-parse (string &optional form)
   "Parse an ISO 8601 date/time string and return a `decode-time' structure.
 
@@ -140,7 +145,7 @@ See `decode-time' for the meaning of FORM."
         (setf (decoded-time-zone date)
               ;; The time zone in decoded times are in seconds.
              (* (iso8601-parse-zone zone-string) 60))
-       (setf (decoded-time-dst date) nil))
+       (setf (decoded-time-dst date) (iso8601--zone-dst zone-string)))
       date)))
 
 (defun iso8601-parse-date (string)
@@ -256,6 +261,7 @@ See `decode-time' for the meaning of FORM."
           (iso8601--decoded-time :hour hour
                                  :minute (or minute 0)
                                  :second (or second 0)
+                                :dst (iso8601--zone-dst zone)
                                  :zone (and zone
                                             (* 60 (iso8601-parse-zone
                                                    zone)))))))))
@@ -364,7 +370,7 @@ Return the number of minutes."
 
 (cl-defun iso8601--decoded-time (&key second minute hour
                                       day month year
-                                      dst zone)
+                                     (dst -1) zone)
   (list (iso8601--value second)
         (iso8601--value minute)
         (iso8601--value hour)
@@ -372,7 +378,7 @@ Return the number of minutes."
         (iso8601--value month)
         (iso8601--value year)
         nil
-       (if (or dst zone) dst -1)
+       dst
         zone))
 
 (defun iso8601--encode-time (time)
diff --git a/test/lisp/calendar/iso8601-tests.el 
b/test/lisp/calendar/iso8601-tests.el
index 6c9e85ec92..f64c498c02 100644
--- a/test/lisp/calendar/iso8601-tests.el
+++ b/test/lisp/calendar/iso8601-tests.el
@@ -82,9 +82,9 @@
   (should (equal (iso8601-parse "2008-03-02T13:47:30Z")
                  '(30 47 13 2 3 2008 nil nil 0)))
   (should (equal (iso8601-parse "2008-03-02T13:47:30+01:00")
-                 '(30 47 13 2 3 2008 nil nil 3600)))
+                 '(30 47 13 2 3 2008 nil -1 3600)))
   (should (equal (iso8601-parse "2008-03-02T13:47:30-01")
-                 '(30 47 13 2 3 2008 nil nil -3600))))
+                 '(30 47 13 2 3 2008 nil -1 -3600))))
 
 (ert-deftest test-iso8601-duration ()
   (should (equal (iso8601-parse-duration "P3Y6M4DT12H30M5S")
@@ -221,24 +221,24 @@
 
 (ert-deftest standard-test-time-of-day-zone ()
   (should (equal (iso8601-parse-time "152746+0100")
-                 '(46 27 15 nil nil nil nil nil 3600)))
+                 '(46 27 15 nil nil nil nil -1 3600)))
   (should (equal (iso8601-parse-time "15:27:46+0100")
-                 '(46 27 15 nil nil nil nil nil 3600)))
+                 '(46 27 15 nil nil nil nil -1 3600)))
 
   (should (equal (iso8601-parse-time "152746+01")
-                 '(46 27 15 nil nil nil nil nil 3600)))
+                 '(46 27 15 nil nil nil nil -1 3600)))
   (should (equal (iso8601-parse-time "15:27:46+01")
-                 '(46 27 15 nil nil nil nil nil 3600)))
+                 '(46 27 15 nil nil nil nil -1 3600)))
 
   (should (equal (iso8601-parse-time "152746-0500")
-                 '(46 27 15 nil nil nil nil nil -18000)))
+                 '(46 27 15 nil nil nil nil -1 -18000)))
   (should (equal (iso8601-parse-time "15:27:46-0500")
-                 '(46 27 15 nil nil nil nil nil -18000)))
+                 '(46 27 15 nil nil nil nil -1 -18000)))
 
   (should (equal (iso8601-parse-time "152746-05")
-                 '(46 27 15 nil nil nil nil nil -18000)))
+                 '(46 27 15 nil nil nil nil -1 -18000)))
   (should (equal (iso8601-parse-time "15:27:46-05")
-                 '(46 27 15 nil nil nil nil nil -18000))))
+                 '(46 27 15 nil nil nil nil -1 -18000))))
 
 
 (defun test-iso8601-format-time-string-zone-round-trip (offset-minutes 
z-format)