net/http: update some comments

And move some code to make control flow more obvious.
No functional change.

Change-Id: Iefaa96f664070ab2accade1857e1946e56df6902
Reviewed-on: https://go-review.googlesource.com/34285
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

diff --git a/src/net/http/client.go b/src/net/http/client.go
index fe2b0196ef66840049e8886cc98c18684876079a..7deccff5876e979936f8636412a9a0a4a2970f8d 100644 (file)
--- a/src/net/http/client.go
+++ b/src/net/http/client.go
@@ -274,6 +274,11 @@ func send(ireq *Request, rt RoundTripper, deadline time.Time) (*Response, error)
 // setRequestCancel sets the Cancel field of req, if deadline is
 // non-zero. The RoundTripper's type is used to determine whether the legacy
 // CancelRequest behavior should be used.
+//
+// As background, there are three ways to cancel a request:
+// First was Transport.CancelRequest. (deprecated)
+// Second was Request.Cancel (this mechanism).
+// Third was Request.Context.
 func setRequestCancel(req *Request, rt RoundTripper, deadline time.Time) (stopTimer func(), didTimeout func() bool) {
        if deadline.IsZero() {
                return nop, alwaysFalse
@@ -285,7 +290,7 @@ func setRequestCancel(req *Request, rt RoundTripper, deadline time.Time) (stopTi
        req.Cancel = cancel
 
        doCancel := func() {
-               // The new way:
+               // The newer way (the second way in the func comment):
                close(cancel)
 
                // The legacy compatibility way, used only

diff --git a/src/net/http/transport.go b/src/net/http/transport.go
index f2743efdd7ff66a4a085a9d7e5a11d53c932cff9..571943d6e5cd9935d43005c138e7211a97820964 100644 (file)
--- a/src/net/http/transport.go
+++ b/src/net/http/transport.go
@@ -923,6 +923,9 @@ func (t *Transport) getConn(treq *transportRequest, cm connectMethod) (*persistC
                // value.
                select {
                case <-req.Cancel:
+                       // It was an error due to cancelation, so prioritize that
+                       // error value. (Issue 16049)
+                       return nil, errRequestCanceledConn
                case <-req.Context().Done():
                        return nil, req.Context().Err()
                case err := <-cancelc:
@@ -935,9 +938,6 @@ func (t *Transport) getConn(treq *transportRequest, cm connectMethod) (*persistC
                        // return the original error message:
                        return nil, v.err
                }
-               // It was an error due to cancelation, so prioritize that
-               // error value. (Issue 16049)
-               return nil, errRequestCanceledConn
        case pc := <-idleConnCh:
                // Another request finished first and its net.Conn
                // became available before our dial. Or somebody