bug#72570: 31.0.50; Regression in date-to-time

[Ulrich Mueller <ulm@gentoo.org>]

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>>>>> On Tue, 13 Aug 2024, Paul Eggert wrote:

> If that's the only reason it's there, we can simply remove the call to
> timezone-make-date-arpa-standard. That would be better to coating the
> pig with even more lipstick.

The attached patch does the former, and also adds some test cases.


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From ccb2d7282cb792ae993b94821ae7bf1d79f4d348 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ulrich=20M=C3=BCller?= <ulm@gentoo.org>
Date: Wed, 14 Aug 2024 13:57:16 +0200
Subject: [PATCH] Drop fallback code in date-to-time, update documentation

* lisp/calendar/time-date.el (date-to-time): Drop fallback code.
Document that the default timezone is local time, rather than GMT.
* test/lisp/calendar/time-date-tests.el (test-date-to-time):
Add more test cases.
* doc/lispref/os.texi (Time Parsing): Document that 'date-to-time'
defaults to local time.  (Bug#72570)
---
 doc/lispref/os.texi                   |  4 ++--
 lisp/calendar/time-date.el            | 19 ++++---------------
 test/lisp/calendar/time-date-tests.el | 24 ++++++++++++++++++++++--
 3 files changed, 28 insertions(+), 19 deletions(-)

diff --git a/doc/lispref/os.texi b/doc/lispref/os.texi
index 5839de4a650..ddaa1de221c 100644
--- a/doc/lispref/os.texi
+++ b/doc/lispref/os.texi
@@ -1788,8 +1788,8 @@ Time Parsing
 This function parses the time-string @var{string} and returns the
 corresponding Lisp timestamp.  The argument @var{string} should represent
 a date-time, and should be in one of the forms recognized by
-@code{parse-time-string} (see below).  This function assumes Universal
-Time if @var{string} lacks explicit time zone information,
+@code{parse-time-string} (see below).  This function assumes local time
+if @var{string} lacks explicit time zone information,
 and assumes earliest values if @var{string} lacks month, day, or time.
 The operating system limits the range of time and zone values.
 @end defun
diff --git a/lisp/calendar/time-date.el b/lisp/calendar/time-date.el
index eca80f1e8b6..717cb4a5c5b 100644
--- a/lisp/calendar/time-date.el
+++ b/lisp/calendar/time-date.el
@@ -145,30 +145,19 @@ encode-time-value
 (autoload 'timezone-make-date-arpa-standard "timezone")
 
 ;;;###autoload
-;; `parse-time-string' isn't sufficiently general or robust.  It fails
-;; to grok some of the formats that timezone does (e.g. dodgy
-;; post-2000 stuff from some Elms) and either fails or returns bogus
-;; values.  timezone-make-date-arpa-standard should help.
 (defun date-to-time (date)
   "Parse a string DATE that represents a date-time and return a time value.
 DATE should be in one of the forms recognized by `parse-time-string'.
-If DATE lacks timezone information, GMT is assumed."
+If DATE lacks timezone information, local time is assumed."
   (condition-case err
       (let ((parsed (parse-time-string date)))
 	(when (decoded-time-year parsed)
 	  (decoded-time-set-defaults parsed))
 	(encode-time parsed))
     (error
-     (let ((overflow-error '(error "Specified time is not representable")))
-       (if (equal err overflow-error)
-	   (signal (car err) (cdr err))
-	 (condition-case err
-	     (encode-time (parse-time-string
-			   (timezone-make-date-arpa-standard date)))
-	   (error
-	    (if (equal err overflow-error)
-		(signal (car err) (cdr err))
-	      (error "Invalid date: %s" date)))))))))
+     (if (equal err '(error "Specified time is not representable"))
+	 (signal (car err) (cdr err))
+       (error "Invalid date: %s" date)))))
 
 ;;;###autoload
 (defalias 'time-to-seconds #'float-time)
diff --git a/test/lisp/calendar/time-date-tests.el b/test/lisp/calendar/time-date-tests.el
index 6512dd0bd07..f8e434e17b1 100644
--- a/test/lisp/calendar/time-date-tests.el
+++ b/test/lisp/calendar/time-date-tests.el
@@ -42,8 +42,28 @@ test-obsolete-encode-time-value
                  '(1 2 3 4))))
 
 (ert-deftest test-date-to-time ()
-  (should (equal (format-time-string "%F %T" (date-to-time "2021-12-04"))
-                 "2021-12-04 00:00:00")))
+  (let ((date-list
+         '(("2021-12-04"                   (00 00 00 04 12 2021 nil -1 nil))
+           ("2006-05-04T03:02:01Z"         (01 02 03 04 05 2006 nil nil 0))
+           ;; Test cases from timezone-parse-date docstring
+           ("14 Apr 89 03:20"              (00 20 03 14 04 1989 nil -1 nil))
+           ("14 Apr 89 03:20:12 GMT"       (12 20 03 14 04 1989 nil nil 0))
+           ("Fri, 17 Mar 89 4:01"          (00 01 04 17 03 1989 nil -1 nil))
+           ("Fri, 17 Mar 89 4:01:33 GMT"   (33 01 04 17 03 1989 nil nil 0))
+           ("Mon Jan 16 16:12 1989"        (00 12 16 16 01 1989 nil -1 nil))
+           ("Mon Jan 16 16:12:37 GMT 1989" (37 12 16 16 01 1989 nil nil 0))
+           ("Thu, 11 Apr 16:17:12 91"      (12 17 16 11 04 1991 nil -1 nil))
+           ("Mon, 6  Jul 16:47:20 T 1992"  (20 47 16 06 07 1992 nil -1 nil))
+           ("1996-06-24 21:13:12"          (12 13 21 24 06 1996 nil -1 nil))
+           ("19960624t211312"              (12 13 21 24 06 1996 nil -1 nil))
+           ;; These are parsed incorrectly:
+           ;; "6 May 1992 1641-JST (Wednesday)"
+           ;; "22-AUG-1993 10:59:12.82"
+           ;; "1996-06-24 21:13-ZONE"
+           )))
+    (dolist (date date-list)
+      (should (equal (date-to-time (car date))
+                     (encode-time (cadr date)))))))
 
 (ert-deftest test-days-between ()
   (should (equal (days-between "2021-10-22" "2020-09-29") 388)))
-- 
2.45.2