Make rawdatastore API safer for writing filters.

impl/prod/info.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 (
         "time"
 
         "github.com/luci/gae/service/info"
         "golang.org/x/net/context"
         "google.golang.org/appengine"
 )
 
+type key int
+
+var namespaceCopyKey key
+
 // useGI adds a gae.GlobalInfo implementation to context, accessible
 // by gae.GetGI(c)
 func useGI(c context.Context) context.Context {
+        // TODO(iannucci): make a better way to get the initial namespace?
+        c = context.WithValue(c, namespaceCopyKey, "")
         return info.SetFactory(c, func(ci context.Context) info.Interface {
                 return giImpl{ci}
         })
 }
 
 type giImpl struct{ context.Context }
 
 func (g giImpl) AccessToken(scopes ...string) (token string, expiry time.Time, err error) {
         return appengine.AccessToken(g, scopes...)
 }
 func (g giImpl) AppID() string {
         return appengine.AppID(g)
 }
+func (g giImpl) GetNamespace() string {
+        return g.Value(namespaceCopyKey).(string)
+}
 func (g giImpl) Datacenter() string {
         return appengine.Datacenter(g)
 }
 func (g giImpl) DefaultVersionHostname() string {
         return appengine.DefaultVersionHostname(g)
 }
 func (g giImpl) InstanceID() string {
         return appengine.InstanceID()
 }
 func (g giImpl) IsDevAppServer() bool {
         return appengine.IsDevAppServer()
 }
 func (g giImpl) IsOverQuota(err error) bool {
         return appengine.IsOverQuota(err)
 }
 func (g giImpl) IsTimeoutError(err error) bool {
         return appengine.IsTimeoutError(err)
 }
 func (g giImpl) ModuleHostname(module, version, instance string) (string, error) {
         return appengine.ModuleHostname(g, module, version, instance)
 }
 func (g giImpl) ModuleName() (name string) {
         return appengine.ModuleName(g)
 }
 func (g giImpl) Namespace(namespace string) (context.Context, error) {
-        return appengine.Namespace(g, namespace)
+        c, err := appengine.Namespace(g, namespace)
+        if err != nil {
+                return c, err
+        }
+        return context.WithValue(c, namespaceCopyKey, namespace), nil
 }
 func (g giImpl) PublicCertificates() ([]info.Certificate, error) {
         certs, err := appengine.PublicCertificates(g)
         if err != nil {
                 return nil, err
         }
         ret := make([]info.Certificate, len(certs))
         for i, c := range certs {
                 ret[i] = info.Certificate(c)
         }
         return ret, nil
 }
 func (g giImpl) RequestID() string {
         return appengine.RequestID(g)
 }
 func (g giImpl) ServerSoftware() string {
         return appengine.ServerSoftware()
 }
 func (g giImpl) ServiceAccount() (string, error) {
         return appengine.ServiceAccount(g)
 }
 func (g giImpl) SignBytes(bytes []byte) (keyName string, signature []byte, err error) {
         return appengine.SignBytes(g, bytes)
 }
 func (g giImpl) VersionID() string {
         return appengine.VersionID(g)
 }