code review 4603041: http: fix serialization of 0-lengthed requests

http: fix handling of 0-lengthed http requests

Via Russ Ross' bug report on golang-nuts, it was not possible
to send an HTTP request with a zero length body with either a
Content-Length (it was stripped) or chunking (it wasn't set).

This means Go couldn't upload 0-length objects to Amazon S3.
(which aren't as silly as they might sound, as S3 objects can
have key/values associated with them, set in the headers)

Amazon further doesn't supported chunked uploads. (not Go's
problem, but we should be able to let users set an explicit
Content-Length, even if it's zero.)

To fix the ambiguity of an explicit zero Content-Length and
the Request struct's default zero value, users need to
explicit set TransferEncoding to []string{"identity"} to force
the Request.Write to include a Content-Length: 0.  identity is
in RFC 2616 but is ignored pretty much everywhere.  We don't
even then serialize it on the wire, since it's kinda useless,
except as an internal sentinel value.

The "identity" value is then documented, but most users can
ignore that because NewRequest now sets that.

And adds more tests.

[bradfitz, 2011-06-08 22:15:13]

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

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

[rsc, 2011-06-08 22:46:56]

LGTM

[bradfitz, 2011-06-08 22:59:30]

*** Submitted as http://code.google.com/p/go/source/detail?r=58a6bdac3d12 ***

http: fix handling of 0-lengthed http requests

Via Russ Ross' bug report on golang-nuts, it was not possible
to send an HTTP request with a zero length body with either a
Content-Length (it was stripped) or chunking (it wasn't set).

This means Go couldn't upload 0-length objects to Amazon S3.
(which aren't as silly as they might sound, as S3 objects can
have key/values associated with them, set in the headers)

Amazon further doesn't supported chunked uploads. (not Go's
problem, but we should be able to let users set an explicit
Content-Length, even if it's zero.)

To fix the ambiguity of an explicit zero Content-Length and
the Request struct's default zero value, users need to
explicit set TransferEncoding to []string{"identity"} to force
the Request.Write to include a Content-Length: 0.  identity is
in RFC 2616 but is ignored pretty much everywhere.  We don't
even then serialize it on the wire, since it's kinda useless,
except as an internal sentinel value.

The "identity" value is then documented, but most users can
ignore that because NewRequest now sets that.

And adds more tests.

R=golang-dev, rsc
CC=golang-dev
http://codereview.appspot.com/4603041

[rsc, 2011-06-09 00:53:13]

btw, it occurred to me a little later that this could just work
if with Content-Length 0 the code tried to read 1 byte before
deciding to use chunked.  it's not super clean but it's no more
ugly than having to remember to say {"identity"}, and less work
for users.

[bradfitz, 2011-06-09 00:57:39]

Cute!  I like it.

I can update the code.

On Wed, Jun 8, 2011 at 5:53 PM, Russ Cox <rsc@golang.org> wrote:

> btw, it occurred to me a little later that this could just work
> if with Content-Length 0 the code tried to read 1 byte before
> deciding to use chunked.  it's not super clean but it's no more
> ugly than having to remember to say {"identity"}, and less work
> for users.
>