[logdog/common/types] add Valid method to StreamAddr.

logdog/common/types/streamaddr.go

 // Copyright 2017 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package types
 
 import (
         "flag"
         "net/url"
         "strings"
@@ skipping 21 matching lines @@
 // Set implements flag.Value
 func (s *StreamAddr) Set(v string) error {
         a, err := ParseURL(v)
         if err != nil {
                 return err
         }
         *s = *a
         return nil
 }
 
+// Validate returns an error if the supplied StreamAddr is not valid.
+func (s *StreamAddr) Validate() error {
+        if s.Host == "" {
+                return errors.New("cannot have empty Host")
+        }
+        if err := s.Project.Validate(); err != nil {
+                return err
+        }
+        if err := s.Path.Validate(); err != nil {
+                return err
+        }
+        return nil
+}
+
+// IsZero returns true iff all fields are empty.
+func (s *StreamAddr) IsZero() bool {
+        return s.Host == "" && s.Path == "" && s.Project == ""
+}
+
 // String returns a string representation of this address.
 func (s *StreamAddr) String() string { return s.URL().String() }
 
 // URL returns a LogDog URL that represents this Stream.
 func (s *StreamAddr) URL() *url.URL {
         return &url.URL{
                 Scheme: logDogURLScheme,
                 Host:   s.Host,
                 Path:   strings.Join([]string{"", string(s.Project), string(s.Path)}, "/"),
         }
@@ skipping 35 matching lines @@
         }
 
         if err := addr.Path.Validate(); err != nil {
                 return nil, errors.Annotate(err).Reason("invalid stream path: %(path)q").
                         D("path", addr.Path).
                         Err()
         }
 
         return &addr, nil
 }