bug#49017: 28.0.50; fractions in iso8601-parse-time sometimes off

bug#49017: 28.0.50; fractions in iso8601-parse-time sometimes off

[J.P.]

[-- Attachment #1: Type: text/plain, Size: 4345 bytes --]

Severity: minor
Tags: patch

I think the function `iso8601-parse-time' may be giving questionable
output when fed a string containing fractional seconds.

  (car (iso8601-parse-time "10:20:30.000001" t))
    ⇒ (301 . 10)

  ;; (30000001 . 1000000) ; expected

I've attempted a fix by taking the dumbest possible route, but it may be
too dumb for the likes of Emacs (or just plain wrong). If that's the
case, please forgive. Thanks.


In GNU Emacs 28.0.50 (build 1, x86_64-redhat-linux-gnu, GTK+ Version 3.24.29, cairo version 1.17.4)
 of 2021-06-13 built on localhost
Repository revision: 2f7a115a9c876e69296974e8e02ece569df988e9
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12011000
System Description: Fedora 34 (Workstation Edition)

Configured using:
 'configure --enable-check-lisp-object-type --enable-checking=yes,glyphs
 --build=x86_64-redhat-linux-gnu --host=x86_64-redhat-linux-gnu
 --program-prefix= --prefix=/usr --exec-prefix=/usr --bindir=/usr/bin
 --sbindir=/usr/sbin --sysconfdir=/etc --datadir=/usr/share
 --includedir=/usr/include --libdir=/usr/lib64 --libexecdir=/usr/libexec
 --localstatedir=/var --sharedstatedir=/var/lib --mandir=/usr/share/man
 --infodir=/usr/share/info --with-dbus --with-gif --with-jpeg --with-png
 --with-rsvg --with-tiff --with-xft --with-xpm --with-x-toolkit=gtk3
 --with-gpm=no --with-xwidgets --with-modules --with-harfbuzz
 --with-cairo --with-json build_alias=x86_64-redhat-linux-gnu
 host_alias=x86_64-redhat-linux-gnu CC=gcc 'CFLAGS=-O0 -g3'
 LDFLAGS=-Wl,-z,relro
 PKG_CONFIG_PATH=:/usr/lib64/pkgconfig:/usr/share/pkgconfig'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GSETTINGS HARFBUZZ JPEG JSON
LCMS2 LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 M17N_FLT MODULES NOTIFY
INOTIFY PDUMPER PNG RSVG SECCOMP SOUND THREADS TIFF TOOLKIT_SCROLL_BARS
X11 XDBE XIM XPM XWIDGETS GTK3 ZLIB

Important settings:
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc puny dired dired-loaddefs
rfc822 mml mml-sec epa derived epg epg-config gnus-util rmail
rmail-loaddefs auth-source cl-seq eieio eieio-core cl-macs
eieio-loaddefs password-cache json map text-property-search time-date
subr-x seq byte-opt gv bytecomp byte-compile cconv mm-decode mm-bodies
mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader cl-loaddefs
cl-lib sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils
iso-transl tooltip eldoc electric uniquify ediff-hook vc-hooks
lisp-float-type mwheel term/x-win x-win term/common-win x-dnd tool-bar
dnd fontset image regexp-opt fringe tabulated-list replace newcomment
text-mode elisp-mode lisp-mode prog-mode register page tab-bar menu-bar
rfn-eshadow isearch easymenu timer select scroll-bar mouse jit-lock
font-lock syntax font-core term/tty-colors frame minibuffer cl-generic
cham georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao
korean japanese eucjp-ms cp51932 hebrew greek romanian slovak czech
european ethiopic indian cyrillic chinese composite charscript charprop
case-table epa-hook jka-cmpr-hook help simple abbrev obarray
cl-preloaded nadvice button loaddefs faces cus-face macroexp files
window text-properties overlay sha1 md5 base64 format env code-pages
mule custom widget hashtable-print-readable backquote threads
xwidget-internal dbusbind inotify lcms2 dynamic-setting
system-font-setting font-render-setting cairo move-toolbar gtk x-toolkit
x multi-tty make-network-process emacs)

Memory information:
((conses 16 51751 11269)
 (symbols 48 6606 1)
 (strings 32 18276 2432)
 (string-bytes 1 614395)
 (vectors 16 13358)
 (vector-slots 8 178597 13456)
 (floats 8 21 45)
 (intervals 56 279 0)
 (buffers 992 11))

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: 0001-Use-string-length-for-fraction-in-iso8601-parse-time.patch --]
[-- Type: text/x-patch, Size: 3451 bytes --]

From 22d1d026a5edc6cc6f85e4fe522ed29bf0a23f16 Mon Sep 17 00:00:00 2001
From: "F. Jason Park" <jp@neverwas.me>
Date: Sun, 13 Jun 2021 23:50:47 -0700
Subject: [PATCH] Use string length for fraction in iso8601-parse-time

* lisp/calendar/iso8601.el (iso8601-parse-time): Replace arithmetic
operation to count number of digits in fractional seconds of time
value.  Use number of text chars in regexp match (range 0-9)
instead.

* test/lisp/calendar/iso8601-tests.el
(nonstandard-test-time-of-day-decimals): Add test case for above.
---
 lisp/calendar/iso8601.el            | 21 ++++++++++-----------
 test/lisp/calendar/iso8601-tests.el |  4 +++-
 2 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/lisp/calendar/iso8601.el b/lisp/calendar/iso8601.el
index 44c4811984..a2f843e643 100644
--- a/lisp/calendar/iso8601.el
+++ b/lisp/calendar/iso8601.el
@@ -226,22 +226,21 @@ iso8601-parse-time
           (zone (match-string 2 string)))
       (if (not (iso8601--match iso8601--time-match time))
           (signal 'wrong-type-argument string)
-        (let ((hour (string-to-number (match-string 1 time)))
-              (minute (and (match-string 2 time)
-                           (string-to-number (match-string 2 time))))
-              (second (and (match-string 3 time)
-                           (string-to-number (match-string 3 time))))
-	      (fraction (and (not (zerop (length (match-string 4 time))))
-                             (string-to-number (match-string 4 time)))))
+        (let* ((hour (string-to-number (match-string 1 time)))
+               (minute (and (match-string 2 time)
+                            (string-to-number (match-string 2 time))))
+               (second (and (match-string 3 time)
+                            (string-to-number (match-string 3 time))))
+               (frac-prec (length (match-string 4 time)))
+               (fraction (and (not (zerop frac-prec))
+                              (string-to-number (match-string 4 time)))))
           (when (and fraction
                      (eq form t))
             (cond
              ;; Sub-second time.
              (second
-              (let ((digits (1+ (truncate (log fraction 10)))))
-                (setq second (cons (+ (* second (expt 10 digits))
-                                      fraction)
-                                   (expt 10 digits)))))
+              (setq second (cons (+ (* second (expt 10 frac-prec)) fraction)
+                                 (expt 10 frac-prec))))
              ;; Fractional minute.
              (minute
               (setq second (iso8601--decimalize fraction 60)))
diff --git a/test/lisp/calendar/iso8601-tests.el b/test/lisp/calendar/iso8601-tests.el
index 618e5b1238..59292c063c 100644
--- a/test/lisp/calendar/iso8601-tests.el
+++ b/test/lisp/calendar/iso8601-tests.el
@@ -183,7 +183,9 @@ nonstandard-test-time-of-day-decimals
   (should (equal (iso8601-parse-time "15:27:35.123" t)
 		  '((35123 . 1000) 27 15 nil nil nil nil -1 nil)))
   (should (equal (iso8601-parse-time "15:27:35.123456789" t)
-		  '((35123456789 . 1000000000) 27 15 nil nil nil nil -1 nil))))
+		 '((35123456789 . 1000000000) 27 15 nil nil nil nil -1 nil)))
+  (should (equal (iso8601-parse-time "15:27:35.012345678" t)
+		 '((35012345678 . 1000000000) 27 15 nil nil nil nil -1 nil))))
 
 (ert-deftest standard-test-time-of-day-beginning-of-day ()
   (should (equal (iso8601-parse-time "000000")
-- 
2.31.1

bug#49017: 28.0.50; fractions in iso8601-parse-time sometimes off

[Lars Ingebrigtsen]

"J.P." <jp@neverwas.me> writes:

> I think the function `iso8601-parse-time' may be giving questionable
> output when fed a string containing fractional seconds.
>
>   (car (iso8601-parse-time "10:20:30.000001" t))
>     ⇒ (301 . 10)
>
>   ;; (30000001 . 1000000) ; expected
>
> I've attempted a fix by taking the dumbest possible route, but it may be
> too dumb for the likes of Emacs (or just plain wrong). If that's the
> case, please forgive. Thanks.

:-)

It was almost perfect -- but didn't handle the case of trailing zeroes
correctly.  That is, it would give different results for these two:

(iso8601-parse-time "10:20:30.000001" t)
(iso8601-parse-time "10:20:30.000001000" t)

I've now pushed a fix based on your patch to Emacs 28.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no