Fix bugs in service/datastore

service/datastore/index.go

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package datastore
 
 import (
         "bytes"
         "fmt"
         "strings"
@@ skipping 199 matching lines @@
 // indexes.
 func (id *IndexDefinition) Builtin() bool {
         return !id.Ancestor && len(id.SortBy) <= 1
 }
 
 // Compound returns true iff this IndexDefinition is a valid compound index
 // definition.
 //
 // NOTE: !Builtin() does not imply Compound().
 func (id *IndexDefinition) Compound() bool {
-        if id.Kind == "" || len(id.SortBy) <= 1 {
+        if id.Kind == "" || id.Builtin() {
                 return false
         }
         for _, sb := range id.SortBy {
                 if sb.Property == "" || sb.Property == "__ancestor__" {
                         return false
                 }
         }
         return true
 }
 
 // YAMLString returns the YAML representation of this IndexDefinition.
 //
 // If the index definition is Builtin() or not Compound(), this will return
 // an error.
 func (id *IndexDefinition) YAMLString() (string, error) {
         if id.Builtin() || !id.Compound() {
-                return "", fmt.Errorf("cannot generate YAML for this IndexDefinition")
+                return "", fmt.Errorf("cannot generate YAML for %s", id)
         }
 
         ret := bytes.Buffer{}
 
         first := true
         ws := func(s string, indent int) {
                 nl := "\n"
                 if first {
                         nl = ""
                         first = false
@@ skipping 43 matching lines @@
         }
         for _, sb := range id.SortBy {
                 wr('/')
                 if sb.Descending {
                         wr('-')
                 }
                 ws(sb.Property)
         }
         return ret.String()
 }