bug#50195: [PATCH] Adding diary-offset to diary-lib.el

[Yuchen Pei]

Sorry, forgot the attach the patch. Here it is.

From 4df9db3eeb3b048579768050ae7bb413fefe9557 Mon Sep 17 00:00:00 2001
From: Yuchen Pei <hi@ypei.me>
Date: Wed, 25 Aug 2021 13:37:20 +1000
Subject: [PATCH] Adding diary-offset to diary-lib.el.

A new diary sexp that offsets another diary sexp (Bug#50195).

* doc/emacs/calendar.texi: Document the change.
* lisp/calendar/diary-lib.el (diary-offset):
* test/lisp/calendar/icalendar-tests.el: Add a test.
---
 doc/emacs/calendar.texi               | 14 ++++++++++++++
 etc/NEWS                              |  8 ++++++++
 lisp/calendar/diary-lib.el            | 11 +++++++++++
 test/lisp/calendar/icalendar-tests.el |  7 +++++++
 4 files changed, 40 insertions(+)

diff --git a/doc/emacs/calendar.texi b/doc/emacs/calendar.texi
index 3750e78e70..18de721e28 100644
--- a/doc/emacs/calendar.texi
+++ b/doc/emacs/calendar.texi
@@ -1363,6 +1363,20 @@ Special Diary Entries
 Thursday of January, February, and March.  If the month is @code{t}, the
 entry applies to all months of the year.
 
+@findex diary-offset
+@example
+%%(diary-offset '(diary-float t 3 4) 2) Monthly committee meeting
+@end example
+
+@noindent
+This entry applies to the Saturday after the third Thursday of each
+month.  The 2 specifies number of days after when the sexp
+@w{@code{'(diary-float t 3 4)}} would evaluate to @code{t}.  This is
+useful when for example your organization has a committee meeting two
+days after every monthly meeting which takes place on the third
+Thursday, or if you would like to attend a virtual meeting scheduled
+in a different timezone causing a difference in the date.
+
   Each of the standard sexp diary entries takes an optional parameter
 specifying the name of a face or a single-character string to use when
 marking the entry in the calendar.  Most generally, sexp diary entries
diff --git a/etc/NEWS b/etc/NEWS
index 07a78216b8..52774b3463 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -2800,6 +2800,14 @@ never be narrower than 19 characters.
 'gomoku-move-sw' and 'gomoku-move-ne' now work correctly, and
 horizontal movements now stop at the edge of the board.
 
++++
+*** New diary sexp 'diary-offset'.
+It offsets another diary sexp by a number of days.  This is useful
+when for example your organization has a committee meeting two days
+after every monthly meeting which takes place on the third Thursday,
+or if you would like to attend a virtual meeting scheduled in a
+different timezone causing a difference in the date.
+
 ** xterm-mouse mode
 
 ---
diff --git a/lisp/calendar/diary-lib.el b/lisp/calendar/diary-lib.el
index f57fe26058..f71392b97f 100644
--- a/lisp/calendar/diary-lib.el
+++ b/lisp/calendar/diary-lib.el
@@ -2014,6 +2014,17 @@ diary-cyclic
     (and (>= diff 0) (zerop (% diff n))
          (cons mark (format entry cycle (diary-ordinal-suffix cycle))))))
 
+;; To be called from diary-sexp-entry, where DATE, ENTRY are bound.
+(defun diary-offset (sexp days)
+  "Offsetted diary entry. Offsets SEXP by DAYS days.
+Entry applies if the date is DAYS days after another diary-sexp SEXP."
+  (with-no-warnings (defvar date))
+  (or (integerp days) (user-error "Days must be an integer"))
+  (let ((date
+        (calendar-gregorian-from-absolute
+         (- (calendar-absolute-from-gregorian date) days))))
+    (eval sexp)))
+
 (defun diary-day-of-year ()
   "Day of year and number of days remaining in the year of date diary entry."
   (with-no-warnings (defvar date))
diff --git a/test/lisp/calendar/icalendar-tests.el 
b/test/lisp/calendar/icalendar-tests.el
index 6973f7e5c9..de2a891758 100644
--- a/test/lisp/calendar/icalendar-tests.el
+++ b/test/lisp/calendar/icalendar-tests.el
@@ -1442,6 +1442,13 @@ icalendar-real-world
 SUMMARY:ff birthday (%d years old)")
 
 
+  (icalendar-tests--test-export
+   nil
+   nil
+   "%%(diary-offset '(diary-float t 3 4) 1) asdf"
+   nil)
+
+
   ;; FIXME!
 
   ;; export 2004-10-28 monthly, weekly entries
-- 
2.33.0


Yuchen Pei <hi@ypei.me> writes:

> Thanks for the comments.
> Eli Zaretskii <eliz@gnu.org> writes:
>
> > > From: Yuchen Pei <hi@ypei.me>
> > > Date: Wed, 25 Aug 2021 13:46:48 +1000
> > > See below my first patch to Emacs.  The copyright assignment 
> > > has already been done BTW.
> >
> > Congrats, and welcome aboard.
> >
> > > Let me know what you think.
> >
> > Some minor comments below.
> >
> > > Would you like me to add some tests?
> >
> > Adding more tests is always welcome, thanks.
>
> All diary sexp tests are in icalendar tests, but diary-offset 
> does not
> easily translate to icalendar events (exporting to icalendar for 
> this
> sexp is rather complicated if not impossible as it applies on 
> top of
> another arbitrary sexp), so I am just adding a simple no-op-like 
> test.
>
> > > Subject: [PATCH] Adding diary-offset, a diary-sexp offsetting
> > > another
> > >  diary-sexp.
> >
> > "git am" uses the Subject for the heading line, and this 
> > Subject is
> > too long for that.  Please consider making it shorter.
>
> Done.
>
> > > A bit like diary-remind, as a diary-sexp rather than reminder, 
> > > and
> > > also support both positive and negative offsets.
> > > This is useful when for example your organization has a 
> > > committee
> > > meeting two days after every monthly meeting which takes place 
> > > on
> > > the
> > > third Thursday, or if you would like to attend a virtual 
> > > meeting
> > > scheduled in a different timezone causing a difference in the 
> > > date.
> >
> > The commit log message should include a ChangeLog-style 
> > description
> > of
> > the files and functions where you made the changes.  See 
> > CONTRIBUTE
> > for more details about the format we prefer.
> >
> > Also, please in the next version include the bug number as part 
> > of
> > the
> > log message.
>
> Done.
>
> > > --- a/doc/emacs/calendar.texi
> > > +++ b/doc/emacs/calendar.texi
> > > @@ -1363,6 +1363,20 @@ Special Diary Entries
> > >  Thursday of January, February, and March.  If the month is
> > > @code{t}, the
> > >  entry applies to all months of the year.
> > >  +@findex diary-offset
> > > +@example
> > > +%%(diary-offset '(diary-float t 3 4) 2) Monthly post-event
> > > committee meeting
> >
> > That line is too long, and will overflow the page width in the
> > printed
> > version of the manual.  Please break it in two.
>
> Done. I made it shorter :)
>
> > > +@noindent
> > > +This entry applies to the Saturday after the third Thursday 
> > > of
> > > each
> > > +month.  The 2 specifies number of days after when the sexp
> > > +@samp{'(diary-float t 3 4)} would evaluate to @code{t}.  This 
> > > is
> >    ^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > This should be in @code, not @samp.  I'd also wrap it in 
> > @w{..}, so
> > that it doesn't get broken between two lines.
>
> Done.
>
> > > +(defun diary-offset (sexp days)
> > > +  "Offsetted diary entry.
> >
> > The first line of a doc string should preferably mention the
> > arguments, but without becoming too long, so it could still fit 
> > on a
> > single line.
>
> Done.
>
> > > +  (with-no-warnings (defvar date) (defvar entry))
> >
> > Why did you need this?
>
> The sexp diary-offset itself requires the date supplied by
> diary-sexp-entry.  The sexp passed to diary-offset will ask for 
> both date and entry.  Removed (defvar entry) as this is not 
> needed by
> diary-offset.  After the removel I tested it in org mode and org
> agenda and it works.
>
> > > +  (integerp days)
> >
> > Isn't it better to use an assertion?
>
> Done.  Added a user-error statement like in diary-cyclic.
>
> > Thanks.


--
Best,
Yuchen

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