code review 5634051: time: clean up MarshalJSON, add RFC3339 method

time: clean up MarshalJSON, add RFC3339 method
encoding/xml: handle time.Time as recognized type

The long term plan is to define an interface that time.Time
can implement and that encoding/xml can call, but we are
not going to try to define that interface before Go 1.
Instead, special-case time.Time in package xml, because
it is such a fundamental type, as a stop-gap.
The eventual methods will behave this way.

Fixes issue 2793.

[rsc, 2012-02-06 21:54:40]

Hello golang-dev@googlegroups.com,

I'd like you to review this change to
https://go.googlecode.com/hg/

[rsc, 2012-02-06 21:55:04]

(Fixes issue 2793)

[r, 2012-02-07 00:10:59]

http://codereview.appspot.com/5634051/diff/2001/src/pkg/time/time.go
File src/pkg/time/time.go (right):

http://codereview.appspot.com/5634051/diff/2001/src/pkg/time/time.go#newcode843
src/pkg/time/time.go:843: // Trailing zeros are trimmed from the fraction in the
result.
i'm unclear why this format gets its own method.
if it's just for XML and/or JSON, fine, but it should say so here.
i don't want to establish a precedent for lots of fiddly formatting methods.

http://codereview.appspot.com/5634051/diff/2001/src/pkg/time/time_test.go
File src/pkg/time/time_test.go (right):

http://codereview.appspot.com/5634051/diff/2001/src/pkg/time/time_test.go#new...
src/pkg/time/time_test.go:230: {"call-RFC3339", "call-RFC3339",
"2009-02-04T21:00:57.012345678-08:00"},
please add a test for zero-padding the year. include negative cases.

[rsc, 2012-02-07 01:43:28]

On Mon, Feb 6, 2012 at 19:10,  <r@golang.org> wrote:
> i'm unclear why this format gets its own method.
> if it's just for XML and/or JSON, fine, but it should say so here.
> i don't want to establish a precedent for lots of fiddly formatting
> methods.

Maybe instead we should define a format that means
"as many decimals as it takes" for the fraction.
Any ideas about what the syntax would be?

Russ

[r2, 2012-02-07 02:17:14]

On Feb 7, 2012, at 12:43 PM, Russ Cox wrote:

> On Mon, Feb 6, 2012 at 19:10,  <r@golang.org> wrote:
>> i'm unclear why this format gets its own method.
>> if it's just for XML and/or JSON, fine, but it should say so here.
>> i don't want to establish a precedent for lots of fiddly formatting
>> methods.
> 
> Maybe instead we should define a format that means
> "as many decimals as it takes" for the fraction.
> Any ideas about what the syntax would be?

It's already true that

	.000

means "three digits of fractional second, including trailing zeros". The docs
are clear that it's zeros only. What if we made

	.999

mean "three digits of fractional second, with trailing zeros trimmed"? Keeps
compatibility and his mild mnemonic value (if there are trailing zeros in the
format, you see trailing zeros in the output).

Not sure it's a good idea, but it's a suggestion. 

-rob

[rsc, 2012-02-07 22:01:58]

Hello golang-dev@googlegroups.com, r@golang.org, r@google.com (cc:
golang-dev@googlegroups.com),

Please take another look.

[niemeyer, 2012-02-08 00:12:24]

LGTM

Makes me wonder how we can enable the developer to tweak the format so they can
format according to a given specification needs. I guess a custom type would
work.

[r, 2012-02-08 00:18:44]

LGTM
that turned out well

http://codereview.appspot.com/5634051/diff/9009/src/pkg/time/format.go
File src/pkg/time/format.go (right):

http://codereview.appspot.com/5634051/diff/9009/src/pkg/time/format.go#newcod...
src/pkg/time/format.go:172: case '.': // .000 or .999 - multiple digits of zeros
(only) for fractional seconds.
the rest of the comment is wrong now, but needlessly precise.

// .000 or .999 - repeated digits for fractional seconds.

[rsc, 2012-02-08 04:37:28]

*** Submitted as a4dc8322859a ***

time: clean up MarshalJSON, add RFC3339 method
encoding/xml: handle time.Time as recognized type

The long term plan is to define an interface that time.Time
can implement and that encoding/xml can call, but we are
not going to try to define that interface before Go 1.
Instead, special-case time.Time in package xml, because
it is such a fundamental type, as a stop-gap.
The eventual methods will behave this way.

Fixes issue 2793.

R=golang-dev, r, r, n13m3y3r
CC=golang-dev
http://codereview.appspot.com/5634051