From b494f59c1b99e7bf493b4a031291954e478cdfb0 Mon Sep 17 00:00:00 2001
From: Stephen Sawchuk <sawchuk@gmail.com>
Date: Fri, 7 Nov 2014 12:23:17 -0500
Subject: [PATCH] always return endcursor - fixes #288

---
 lib/datastore/request.js  | 21 ++++++++++-----------
 regression/datastore.js   | 22 ++++++++++------------
 test/datastore/request.js | 24 +++++++++++++++++++-----
 3 files changed, 39 insertions(+), 28 deletions(-)

diff --git a/lib/datastore/request.js b/lib/datastore/request.js
index 7580ef958f3..82b907ffadc 100644
--- a/lib/datastore/request.js
+++ b/lib/datastore/request.js
@@ -308,15 +308,15 @@ DatastoreRequest.prototype.delete = function(keys, callback) {
  * //-
  *
  * // Retrieve 5 companies.
- * transaction.runQuery(queryObject, function(err, entities, nextQuery) {
- *   // `nextQuery` is not null if there are more results.
- *   if (nextQuery) {
- *     transaction.runQuery(nextQuery, function(err, entities, nextQuery) {});
- *   }
+ * transaction.runQuery(queryObject, function(err, entities, endCursor) {
+ *   // Use `endCursor` as the starting cursor for your next query.
+ *   var nextQuery = queryObject.start(endCursor);
+ *   transaction.runQuery(nextQuery, function(err, entities, endCursor) {});
  * });
  */
 DatastoreRequest.prototype.runQuery = function(q, callback) {
   callback = callback || util.noop;
+
   var req = {
     read_options: {},
     query: entity.queryToQueryProto(q)
@@ -333,14 +333,13 @@ DatastoreRequest.prototype.runQuery = function(q, callback) {
       callback(err);
       return;
     }
-    var nextQuery = null;
+
+    var cursor = '';
     if (resp.batch.end_cursor) {
-      var cursor = resp.batch.end_cursor.toBase64();
-      if (cursor !== q.startVal) {
-        nextQuery = q.start(cursor).offset(0);
-      }
+      cursor = resp.batch.end_cursor.toBase64();
     }
-    callback(null, entity.formatArray(resp.batch.entity_result), nextQuery);
+
+    callback(null, entity.formatArray(resp.batch.entity_result), cursor);
   });
 };
 
diff --git a/regression/datastore.js b/regression/datastore.js
index 9c7920c9798..056c3c89420 100644
--- a/regression/datastore.js
+++ b/regression/datastore.js
@@ -231,19 +231,17 @@ describe('datastore', function() {
     it('should limit queries', function(done) {
       var q = ds.createQuery('Character').hasAncestor(ancestor)
           .limit(5);
-      ds.runQuery(q, function(err, firstEntities, secondQuery) {
+      ds.runQuery(q, function(err, firstEntities, firstEndCursor) {
         assert.ifError(err);
         assert.equal(firstEntities.length, 5);
-        assert(secondQuery);
-        ds.runQuery(secondQuery, function(err, secondEntities, thirdQuery) {
+        var secondQ = q.start(firstEndCursor);
+        ds.runQuery(secondQ, function(err, secondEntities, secondEndCursor) {
           assert.ifError(err);
           assert.equal(secondEntities.length, 3);
-          // TODO(silvano): it currently requires an additional request that
-          // brings an empty page and a null query
-          //assert.equal(thirdQuery, null)
-          ds.runQuery(thirdQuery, function(err, thirdEntities, fourthQuery) {
+          var thirdQ = q.start(secondEndCursor);
+          ds.runQuery(thirdQ, function(err, thirdEntities) {
             assert.ifError(err);
-            assert.equal(fourthQuery, null);
+            assert.equal(thirdEntities.length, 0);
             done();
           });
         });
@@ -324,11 +322,12 @@ describe('datastore', function() {
           .offset(2)
           .limit(3)
           .order('appearances');
-      ds.runQuery(q, function(err, entities, secondQuery) {
+      ds.runQuery(q, function(err, entities, endCursor) {
         assert.ifError(err);
         assert.equal(entities.length, 3);
         assert.equal(entities[0].data.name, 'Robb');
         assert.equal(entities[2].data.name, 'Catelyn');
+        var secondQuery = q.start(endCursor).offset(0);
         ds.runQuery(secondQuery, function(err, secondEntities) {
           assert.equal(secondEntities.length, 3);
           assert.equal(secondEntities[0].data.name, 'Sansa');
@@ -343,13 +342,12 @@ describe('datastore', function() {
           .offset(2)
           .limit(2)
           .order('appearances');
-      ds.runQuery(q, function(err, entities, nextQuery) {
+      ds.runQuery(q, function(err, entities, endCursor) {
         assert.ifError(err);
-        var startCursor = nextQuery.startVal;
         var cursorQuery =
             ds.createQuery('Character').hasAncestor(ancestor)
               .order('appearances')
-              .start(startCursor);
+              .start(endCursor);
         ds.runQuery(cursorQuery, function(err, secondEntities) {
           assert.ifError(err);
           assert.equal(secondEntities.length, 4);
diff --git a/test/datastore/request.js b/test/datastore/request.js
index 9841b60b76b..66ee13ff460 100644
--- a/test/datastore/request.js
+++ b/test/datastore/request.js
@@ -329,15 +329,29 @@ describe('Request', function() {
       });
     });
 
-    it('should return a new query if results remain', function() {
+    it('should return an empty string if no end cursor exists', function(done) {
       request.makeReq_ = function(method, req, callback) {
-        assert.equal(method, 'runQuery');
-        callback(null, mockResponse.withResultsAndEndCursor);
+        callback(null, mockResponse.withResults);
+      };
+
+      request.runQuery(query, function(err, entities, endCursor) {
+        assert.ifError(err);
+        assert.strictEqual(endCursor, '');
+        done();
+      });
+    });
+
+    it('should return the end cursor from the last query', function(done) {
+      var response = mockResponse.withResultsAndEndCursor;
+
+      request.makeReq_ = function(method, req, callback) {
+        callback(null, response);
       };
 
-      request.runQuery(query, function(err, entities, nextQuery) {
+      request.runQuery(query, function(err, entities, endCursor) {
         assert.ifError(err);
-        assert.equal(nextQuery.constructor.name, 'Query');
+        assert.equal(endCursor, response.batch.end_cursor.toBase64());
+        done();
       });
     });
   });