From 86dd92c88edff6d59a08f4b955645795c15fa3df Mon Sep 17 00:00:00 2001
From: Jeremy Thurgood <jeremy@praekelt.com>
Date: Fri, 30 Jan 2015 21:29:04 +0200
Subject: [PATCH] The next_page() method on index pages now returns None if
 there is no next page.

---
 vumi/persist/riak_manager.py     | 2 ++
 vumi/persist/tests/test_model.py | 3 +++
 vumi/persist/txriak_manager.py   | 4 +++-
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/vumi/persist/riak_manager.py b/vumi/persist/riak_manager.py
index 2b3a4335c..15bf6cbc8 100644
--- a/vumi/persist/riak_manager.py
+++ b/vumi/persist/riak_manager.py
@@ -62,6 +62,8 @@ def next_page(self):
             A new :class:`VumiIndexPage` object containing the next page of
             results.
         """
+        if not self.has_next_page():
+            return None
         try:
             result = self._index_page.next_page()
         except RiakError as e:
diff --git a/vumi/persist/tests/test_model.py b/vumi/persist/tests/test_model.py
index 2932e8748..ec3a9c502 100644
--- a/vumi/persist/tests/test_model.py
+++ b/vumi/persist/tests/test_model.py
@@ -727,6 +727,9 @@ def test_index_keys_page(self):
         self.assertEqual(sorted(keys3), [])
         self.assertEqual(keys3.has_next_page(), False)
 
+        no_keys = yield keys3.next_page()
+        self.assertEqual(no_keys, None)
+
     @Manager.calls_manager
     def test_index_keys_page_explicit_continuation(self):
         indexed_model = self.manager.proxy(IndexedModel)
diff --git a/vumi/persist/txriak_manager.py b/vumi/persist/txriak_manager.py
index 66e730f89..3fac7848d 100644
--- a/vumi/persist/txriak_manager.py
+++ b/vumi/persist/txriak_manager.py
@@ -7,7 +7,7 @@
 from riak import RiakClient, RiakObject, RiakMapReduce, RiakError
 from twisted.internet.threads import deferToThread
 from twisted.internet.defer import (
-    inlineCallbacks, returnValue, gatherResults, maybeDeferred)
+    inlineCallbacks, returnValue, gatherResults, maybeDeferred, succeed)
 
 from vumi.persist.model import Manager, VumiRiakError
 
@@ -69,6 +69,8 @@ def next_page(self):
             A new :class:`VumiTxIndexPage` object containing the next page of
             results.
         """
+        if not self.has_next_page():
+            return succeed(None)
         d = deferToThread(self._index_page.next_page)
         d.addCallback(type(self))
         d.addErrback(riakErrorHandler)