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List:       git
Subject:    Re: Improve on 'approxidate'
From:       Jeff King <peff () peff ! net>
Date:       2009-08-31 1:58:17
Message-ID: 20090831015817.GA30454 () coredump ! intra ! peff ! net
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On Sun, Aug 30, 2009 at 06:35:58PM -0400, Jeff King wrote:

> > +	tm.tm_year = -1;
> > +	tm.tm_mon = -1;
> > +	tm.tm_mday = -1;
> 
> This breaks relative dates like "3.months.ago", because
> approxidate_alpha needs to see the "current" date in tm (and now it sees
> -1, subtracts from it, and assumes we are just crossing a year boundary
> because of the negative).  3.years.ago is also broken, but I don't think
> 3.days.ago is.
> 
> Probably we just need to pass "now" to approxidate_alpha, and it needs
> to call update_tm under the case for "months" and "years" (and I haven't
> quite figured out why those are not part of the "tl" list).
> Unfortunately, I'm out of time to look at it more right now, but I'll
> take a look tonight or tomorrow if you don't beat me to it.

OK, I looked at it.

The fix is pretty straightforward. We _do_ already pass "now" to
approxidate_alpha, and it looks like you already fixed the "typelen"
array case (which handles seconds, minutes, hours, days, and weeks) by
calling update_tm. But all of those units are convertible to seconds,
and months and years are not, which explains why they are handled
separately.

So I think we can just "cheat" and call update_tm to fill in the fields
from "now" as we would for the other units, and then tweak the "struct
tm" as we did before. I.e.,:

diff --git a/date.c b/date.c
index 8e57e5e..e9ee4aa 100644
--- a/date.c
+++ b/date.c
@@ -857,7 +857,9 @@ static const char *approxidate_alpha(const char *date, struct tm *tm, struct tm
 	}
 
 	if (match_string(date, "months") >= 5) {
-		int n = tm->tm_mon - *num;
+		int n;
+		update_tm(tm, now, 0); /* fill in date fields if needed */
+		n = tm->tm_mon - *num;
 		*num = 0;
 		while (n < 0) {
 			n += 12;
@@ -868,6 +870,7 @@ static const char *approxidate_alpha(const char *date, struct tm *tm, struct tm
 	}
 
 	if (match_string(date, "years") >= 4) {
+		update_tm(tm, now, 0); /* fill in date fields if needed */
 		tm->tm_year -= *num;
 		*num = 0;
 		return end;

I'll wrap this fix up in a commit message with tests and add it to the
"test approxidate" series I'm brewing.

-Peff
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