code review 957045: net: introduce net.Error interface

net: introduce net.Error interface

Adds two more methods, Timeout and Temporary.
Implemented by os.Errno too.  The intent is to make
the checks for os.EAGAIN a little less clunky.
It should also let us clean up a bug that Mike Solomon
pointed out: if a network server gets an "out of file descriptors"
error from Accept, the listener should not stop.
It will be able to check this because that error would
have Temporary() == true.

Also clean up some underscore names.

Fixes issue 442.

[rsc, 2010-04-25 00:50:07]

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

I'd like you to review this change.

[r, 2010-04-25 01:01:45]

LGTM

[rsc, 2010-04-25 01:12:22]

I'm going to sit on this for the weekend.
I think it might make sense to continue to return os.Error
even when a method is guaranteeing net.Error and there
is no interface to satisfy.  The problem is code like in
package http

func ListenAndServe(addr string, handler Handler) os.Error {
	l, e := net.Listen("tcp", addr)
	if e != nil {
		return e
	}
	e = Serve(l, handler)
	l.Close()
	return e
}

Here the e from net.Listen is a net.Error but the one from
Server is an os.Error and cannot be assigned to e.
The fix is to insert as the first line

    var e os.Error

but I don't really like that.

Russ

[r2, 2010-04-25 02:28:31]

yes.

i thought the plan was always to return the generic type and type-switch if we
care.

-rob

On Apr 24, 2010, at 6:12 PM, Russ Cox wrote:

> I'm going to sit on this for the weekend.
> I think it might make sense to continue to return os.Error
> even when a method is guaranteeing net.Error and there
> is no interface to satisfy.  The problem is code like in
> package http
> 
> func ListenAndServe(addr string, handler Handler) os.Error {
> 	l, e := net.Listen("tcp", addr)
> 	if e != nil {
> 		return e
> 	}
> 	e = Serve(l, handler)
> 	l.Close()
> 	return e
> }
> 
> Here the e from net.Listen is a net.Error but the one from
> Server is an os.Error and cannot be assigned to e.
> The fix is to insert as the first line
> 
>    var e os.Error
> 
> but I don't really like that.
> 
> Russ

[rsc, 2010-04-25 23:41:22]

PTAL

Everything is statically typed to os.Error again.

[rsc, 2010-04-26 17:39:19]

Do you want to look again (the "3" link on
http://codereview.appspot.com/957045/show)?
Mostly just lots of os. being added back.

On Sun, Apr 25, 2010 at 16:41, Russ Cox <rsc@golang.org> wrote:
> PTAL
>
> Everything is statically typed to os.Error again.
>

[r, 2010-04-26 18:35:10]

LGTM

[rsc, 2010-04-27 05:15:32]

*** Submitted as http://code.google.com/p/go/source/detail?r=f0e8b341ca6d ***

net: introduce net.Error interface

Adds two more methods, Timeout and Temporary.
Implemented by os.Errno too.  The intent is to make
the checks for os.EAGAIN a little less clunky.
It should also let us clean up a bug that Mike Solomon
pointed out: if a network server gets an "out of file descriptors"
error from Accept, the listener should not stop.
It will be able to check this because that error would
have Temporary() == true.

Also clean up some underscore names.

Fixes issue 442.

R=r
CC=golang-dev, msolo
http://codereview.appspot.com/957045