Add Timeout and IsTimeoutError functions.

This adds the API for controlling and checking for timeouts.
Timeouts aren't actually implemented yet.

Change-Id: I39f189711a058e255fe30b5a1dce3c7d821483c7

timeout.go

@@ -0,0 +1,49 @@
+// Copyright 2013 Google Inc. All rights reserved.
+// Use of this source code is governed by the Apache 2.0
+// license that can be found in the LICENSE file.
+
+package appengine
+
+import (
+	"time"
+
+	"code.google.com/p/goprotobuf/proto"
+
+	"github.com/golang/appengine/internal"
+)
+
+// IsTimeoutError reports whether err is a timeout error.
+func IsTimeoutError(err error) bool {
+	if t, ok := err.(interface {
+		IsTimeout() bool
+	}); ok {
+		return t.IsTimeout()
+	}
+	return false
+}
+
+// Timeout returns a replacement context that uses d as the default API RPC timeout.
+func Timeout(c Context, d time.Duration) Context {
+	return &timeoutContext{
+		Context: c,
+		d:       d,
+	}
+}
+
+type timeoutContext struct {
+	Context
+	d time.Duration
+}
+
+func (t *timeoutContext) Call(service, method string, in, out proto.Message, opts *internal.CallOptions) error {
+	// Only affect calls that don't have a timeout.
+	if opts == nil || opts.Timeout == 0 {
+		newOpts := new(internal.CallOptions)
+		if opts != nil {
+			*newOpts = *opts
+		}
+		newOpts.Timeout = t.d
+		opts = newOpts
+	}
+	return t.Context.Call(service, method, in, out, opts)
+}

timeout_test.go

@@ -0,0 +1,59 @@
+// Copyright 2013 Google Inc. All rights reserved.
+// Use of this source code is governed by the Apache 2.0
+// license that can be found in the LICENSE file.
+
+package appengine
+
+import (
+	"testing"
+	"time"
+
+	"code.google.com/p/goprotobuf/proto"
+
+	"github.com/golang/appengine/internal"
+)
+
+type timeoutRecorder struct {
+	Context
+	d time.Duration
+}
+
+func (tr *timeoutRecorder) Call(_, _ string, _, _ proto.Message, opts *internal.CallOptions) error {
+	tr.d = 5 * time.Second // default
+	if opts != nil {
+		tr.d = opts.Timeout
+	}
+	return nil
+}
+
+func TestTimeout(t *testing.T) {
+	tests := []struct {
+		desc string
+		opts *internal.CallOptions
+		want time.Duration
+	}{
+		{
+			"no opts",
+			nil,
+			6 * time.Second,
+		},
+		{
+			"empty opts",
+			&internal.CallOptions{},
+			6 * time.Second,
+		},
+		{
+			"set opts",
+			&internal.CallOptions{Timeout: 7 * time.Second},
+			7 * time.Second,
+		},
+	}
+	for _, test := range tests {
+		tr := new(timeoutRecorder)
+		c := Timeout(tr, 6*time.Second)
+		c.Call("service", "method", nil, nil, test.opts)
+		if tr.d != test.want {
+			t.Errorf("%s: timeout was %v, want %v", test.desc, tr.d, test.want)
+		}
+	}
+}