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Fix ambiguity in nil DST flag

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Formerly nil meant both that DST was not in effect and that
the DST flag was unknown, and different functions interpreted
the flag differently.  Now the meaning is consistently nil for
DST not in effect, and -1 for DST flag not known.
* doc/lispref/os.texi (Time Conversion): The DST slot is
now three-valued, not two-.
* doc/misc/emacs-mime.texi (time-date): Adjust to new behavior.
* etc/NEWS: Mention this.
* lisp/calendar/parse-time.el (parse-time-string):
* src/editfns.c (Fdecode_time):
Return -1 for unknown DST flag.
* test/lisp/calendar/parse-time-tests.el (parse-time-tests):
Adjust tests to match new behavior, and add a new
test for nil vs -1.
This commit is contained in:
Paul Eggert 2018-09-21 14:24:42 -07:00
parent 167274d44f
commit 0bec064454
6 changed files with 32 additions and 17 deletions
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3
doc/lispref/os.texi
View file

@ -1423,7 +1423,8 @@ The year, an integer typically greater than 1900.
The day of week, as an integer between 0 and 6, where 0 stands for
Sunday.
@item dst
@code{t} if daylight saving time is effect, otherwise @code{nil}.
@code{t} if daylight saving time is effect, @code{nil} if it is not
in effect, and @minus{}1 if this information is not available.
@item utcoff
An integer indicating the Universal Time offset in seconds, i.e., the number of
seconds east of Greenwich.

2
doc/misc/emacs-mime.texi
View file

@ -1535,7 +1535,7 @@ Here's a bunch of time/date/second/day examples:
@example
(parse-time-string "Sat Sep 12 12:21:54 1998 +0200")
@result{} (54 21 12 12 9 1998 6 nil 7200)
@result{} (54 21 12 12 9 1998 6 -1 7200)
(date-to-time "Sat Sep 12 12:21:54 1998 +0200")
@result{} (13818 19266)

8
etc/NEWS
View file

@ -1060,6 +1060,14 @@ a multibyte string even if its second argument is an ASCII character.
** (format "%d" X) no longer mishandles a floating-point number X that
does not fit in a machine integer.
+++
** In the DST slot, encode-time and parse-time-string now return -1
if it is not known whether daylight saving time is in effect.
Formerly they were inconsistent: encode-time returned t in this
situation, whereas parse-time-string returned nil. Now they
consistently use use nil to mean that DST is not in effect, and use -1
to mean that it is not known whether DST is in effect.
** New JSON parsing and serialization functions 'json-serialize',
'json-insert', 'json-parse-string', and 'json-parse-buffer'. These
are implemented in C using the Jansson library.

10
lisp/calendar/parse-time.el
View file

@ -29,8 +29,9 @@
;; `parse-time-string' parses a time in a string and returns a list of 9
;; values, just like `decode-time', where unspecified elements in the
;; string are returned as nil. `encode-time' may be applied on these
;; values to obtain an internal time value.
;; string are returned as nil (except unspecfied DST is returned as -1).
;; `encode-time' may be applied on these values to obtain an internal
;; time value.
;;; Code:
@ -151,8 +152,9 @@ STRING should be on something resembling an RFC2822 string, a la
somewhat liberal in what format it accepts, and will attempt to
return a \"likely\" value even for somewhat malformed strings.
The values returned are identical to those of `decode-time', but
any values that are unknown are returned as nil."
(let ((time (list nil nil nil nil nil nil nil nil nil))
any unknown values other than DST are returned as nil, and an
unknown DST value is returned as -1."
(let ((time (list nil nil nil nil nil nil nil -1 nil))
(temp (parse-time-tokenize (downcase string))))
(while temp
(let ((parse-time-elt (pop temp))

6
src/editfns.c
View file

@ -2165,7 +2165,8 @@ between 0 and 23. DAY is an integer between 1 and 31. MONTH is an
integer between 1 and 12. YEAR is an integer indicating the
four-digit year. DOW is the day of week, an integer between 0 and 6,
where 0 is Sunday. DST is t if daylight saving time is in effect,
otherwise nil. UTCOFF is an integer indicating the UTC offset in
nil if it is not in effect, and -1 if this information is
not available. UTCOFF is an integer indicating the UTC offset in
seconds, i.e., the number of seconds east of Greenwich. (Note that
Common Lisp has different meanings for DOW and UTCOFF.)
@ -2194,7 +2195,8 @@ usage: (decode-time &optional TIME ZONE) */)
make_fixnum (local_tm.tm_mon + 1),
make_fixnum (local_tm.tm_year + tm_year_base),
make_fixnum (local_tm.tm_wday),
local_tm.tm_isdst ? Qt : Qnil,
(local_tm.tm_isdst < 0 ? make_fixnum (-1)
: local_tm.tm_isdst == 0 ? Qnil : Qt),
(HAVE_TM_GMTOFF
? make_fixnum (tm_gmtoff (&local_tm))
: gmtime_r (&time_spec, &gmt_tm)

20
test/lisp/calendar/parse-time-tests.el
View file

@ -28,21 +28,23 @@
(ert-deftest parse-time-tests ()
(should (equal (parse-time-string "Mon, 22 Feb 2016 19:35:42 +0100")
'(42 35 19 22 2 2016 1 nil 3600)))
'(42 35 19 22 2 2016 1 -1 3600)))
(should (equal (parse-time-string "22 Feb 2016 19:35:42 +0100")
'(42 35 19 22 2 2016 nil nil 3600)))
'(42 35 19 22 2 2016 nil -1 3600)))
(should (equal (parse-time-string "22 Feb 2016 +0100")
'(nil nil nil 22 2 2016 nil nil 3600)))
'(nil nil nil 22 2 2016 nil -1 3600)))
(should (equal (parse-time-string "Mon, 22 Feb 16 19:35:42 +0100")
'(42 35 19 22 2 2016 1 nil 3600)))
'(42 35 19 22 2 2016 1 -1 3600)))
(should (equal (parse-time-string "Mon, 22 February 2016 19:35:42 +0100")
'(42 35 19 22 2 2016 1 nil 3600)))
'(42 35 19 22 2 2016 1 -1 3600)))
(should (equal (parse-time-string "Mon, 22 feb 2016 19:35:42 +0100")
'(42 35 19 22 2 2016 1 nil 3600)))
'(42 35 19 22 2 2016 1 -1 3600)))
(should (equal (parse-time-string "Monday, 22 february 2016 19:35:42 +0100")
'(42 35 19 22 2 2016 1 nil 3600)))
(should (equal (parse-time-string "Monday, 22 february 2016 19:35:42 PDT")
'(42 35 19 22 2 2016 1 t -25200)))
'(42 35 19 22 2 2016 1 -1 3600)))
(should (equal (parse-time-string "Monday, 22 february 2016 19:35:42 PST")
'(42 35 19 22 2 2016 1 nil -28800)))
(should (equal (parse-time-string "Friday, 21 Sep 2018 13:47:58 PDT")
'(58 47 13 21 9 2018 5 t -25200)))
(should (equal (parse-iso8601-time-string "1998-09-12T12:21:54-0200")
'(13818 33666)))
(should (equal (parse-iso8601-time-string "1998-09-12T12:21:54-0230")