Clean up callback interfaces.

impl/prod/raw_datastore.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 prod
 
 import (
         ds "github.com/luci/gae/service/datastore"
         "github.com/luci/gae/service/info"
         "github.com/luci/luci-go/common/errors"
@@ skipping 198 matching lines @@
         }
         tf := typeFilter{}
         for {
                 k, err := t.Next(&tf)
                 if err == datastore.Done {
                         return nil
                 }
                 if err != nil {
                         return err
                 }
-                if !cb(dsR2F(k), tf.pm, cfunc) {
-                        return nil
+                if err := cb(dsR2F(k), tf.pm, cfunc); err != nil {
+                        if err == ds.Stop {
+                                return nil
+                        }
+                        return err
                 }
         }
 }
 
 func (d rdsImpl) Count(fq *ds.FinalizedQuery) (int64, error) {
         q, err := d.fixQuery(fq)
         if err != nil {
                 return 0, err
         }
         ret, err := q.Count(d.aeCtx)
         return int64(ret), err
 }
 
 func (d rdsImpl) RunInTransaction(f func(c context.Context) error, opts *ds.TransactionOptions) error {
         ropts := (*datastore.TransactionOptions)(opts)
         return datastore.RunInTransaction(d.aeCtx, func(c context.Context) error {
                 return f(context.WithValue(d.userCtx, prodContextKey, c))
         }, ropts)
 }
 
 func (d rdsImpl) Testable() ds.Testable {
         return nil
 }