[logdog/common/types] make StreamAddr implement flag.Value.

R=dnj@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/2895233004

logdog/common/types/streamaddr.go

@@ -5,6 +5,7 @@
 package types
 
 import (
+	"flag"
 	"net/url"
 	"strings"
 
@@ -26,6 +27,18 @@ type StreamAddr struct {
 	Path StreamPath
 }
 
+var _ flag.Value = (*StreamAddr)(nil)
+
+// Set implements flag.Value
+func (s *StreamAddr) Set(v string) error {
+	a, err := ParseURL(v)
+	if err != nil {
+		return err
+	}
+	*s = *a
+	return nil
+}
+
 // String returns a string representation of this address.
 func (s *StreamAddr) String() string { return s.URL().String() }
 

logdog/common/types/streamaddr_test.go

@@ -5,6 +5,7 @@
 package types
 
 import (
+	"flag"
 	"fmt"
 	"net/url"
 	"testing"
@@ -57,4 +58,25 @@ func TestStreamAddr(t *testing.T) {
 			})
 		}
 	})
+
+	Convey(`StreamAddr is a flag.Value`, t, func() {
+		fs := flag.NewFlagSet("testing", flag.ContinueOnError)
+		a := &StreamAddr{}
+
+		fs.Var(a, "addr", "its totally an address of a thing")
+
+		Convey(`good`, func() {
+			So(fs.Parse([]string{"-addr", "logdog://host/project/a/+/b"}), ShouldBeNil)
+			So(a, ShouldResemble, &StreamAddr{
+				"host",
+				"project",
+				"a/+/b",
+			})
+		})
+
+		Convey(`bad`, func() {
+			So(fs.Parse([]string{"-addr", "://host/project/a/+/b"}), ShouldErrLike,
+				"failed to parse URL")
+		})
+	})
 }