Removing cursor and more results from query object.

This is a follow up to a discussion in #423 and #425.

Also
- Adding fetch_page() method to return the needed properties
  no longer available on the Query object.
- Made fetch_page() fail if more_results is `NOT_FINISHED`, which
  seems to be intended for batched requests.
- Added start_cursor and end_cursor properties to Query.
- Updated docstrings to reflect change
- Updated tests to ensure the returned cursor was always set.
- Streamlined fetch()/fetch_page() tests to run via a single
  tweakable helper.
- Updated a datastore.connection test to construct and return an
  initialized QueryResultBatch to simulate a valid cursor.
- Updated regression.clear_datastore and regression.datastore to
  reflect changed API surface.

gcloud/datastore/connection.py

@@ -289,10 +289,13 @@ def run_query(self, dataset_id, query_pb, namespace=None):
 
         Using the `fetch`` method...
 
-        >>> query.fetch()
+        >>> entities, cursor, more_results = query.fetch_page()
+        >>> entities
         [<list of Entity unmarshalled from protobuf>]
-        >>> query.cursor()
+        >>> cursor
         <string containing cursor where fetch stopped>
+        >>> more_results
+        <boolean of more results>
 
         Under the hood this is doing...
 
@@ -318,7 +321,7 @@ def run_query(self, dataset_id, query_pb, namespace=None):
                              datastore_pb.RunQueryResponse)
         return (
             [e.entity for e in response.batch.entity_result],
-            response.batch.end_cursor,
+            response.batch.end_cursor,  # Assume response always has cursor.
             response.batch.more_results,
             response.batch.skipped_results,
         )

gcloud/datastore/query.py

@@ -56,6 +56,8 @@ class Query(object):
     :param dataset: The namespace to which to restrict results.
     """
 
+    _MORE_RESULTS = datastore_pb.QueryResultBatch.MORE_RESULTS_AFTER_LIMIT
+    _NO_MORE_RESULTS = datastore_pb.QueryResultBatch.NO_MORE_RESULTS
     OPERATORS = {
         '<=': datastore_pb.PropertyFilter.LESS_THAN_OR_EQUAL,
         '>=': datastore_pb.PropertyFilter.GREATER_THAN_OR_EQUAL,
@@ -69,7 +71,6 @@ def __init__(self, kind=None, dataset=None, namespace=None):
         self._dataset = dataset
         self._namespace = namespace
         self._pb = datastore_pb.Query()
-        self._cursor = self._more_results = None
         self._offset = 0
 
         if kind:
@@ -84,8 +85,6 @@ def _clone(self):
         clone = self.__class__(dataset=self._dataset,
                                namespace=self._namespace)
         clone._pb.CopyFrom(self._pb)
-        clone._cursor = self._cursor
-        clone._more_results = self._more_results
         return clone
 
     def namespace(self):
@@ -239,8 +238,8 @@ def kind(self, *kinds):
         :type kinds: string
         :param kinds: The entity kinds for which to query.
 
-        :rtype: string or :class:`Query`
-        :returns: If no arguments, returns the kind.
+        :rtype: string, list of strings, or :class:`Query`
+        :returns: If no arguments, returns the kind or list of kinds.
                   If a kind is provided, returns a clone of the :class:`Query`
                   with those kinds set.
         """
@@ -250,7 +249,13 @@ def kind(self, *kinds):
                 clone._pb.kind.add().name = kind
             return clone
         else:
-            return self._pb.kind
+            # In the proto definition for Query, `kind` is repeated.
+            kind_names = [kind_expr.name for kind_expr in self._pb.kind]
+            num_kinds = len(kind_names)
+            if num_kinds == 1:
+                return kind_names[0]
+            elif num_kinds > 1:
+                return kind_names
 
     def limit(self, limit=None):
         """Get or set the limit of the Query.
@@ -302,8 +307,12 @@ def dataset(self, dataset=None):
         else:
             return self._dataset
 
-    def fetch(self, limit=None):
-        """Executes the Query and returns all matching entities.
+    def fetch_page(self, limit=None):
+        """Executes the Query and returns matching entities, and paging info.
+
+        In addition to the fetched entities, it also returns a cursor to allow
+        paging through a results set and a boolean `more_results` indicating
+        if there are any more.
 
         This makes an API call to the Cloud Datastore, sends the Query
         as a protobuf, parses the responses to Entity protobufs, and
@@ -315,10 +324,10 @@ def fetch(self, limit=None):
           >>> from gcloud import datastore
           >>> dataset = datastore.get_dataset('dataset-id')
           >>> query = dataset.query('Person').filter('name', '=', 'Sally')
-          >>> query.fetch()
-          [<Entity object>, <Entity object>, ...]
-          >>> query.fetch(1)
-          [<Entity object>]
+          >>> query.fetch_page()
+          [<Entity object>, <Entity object>, ...], 'cursorbase64', True
+          >>> query.fetch_page(1)
+          [<Entity object>], 'cursorbase64', True
           >>> query.limit()
           None
 
@@ -328,8 +337,13 @@ def fetch(self, limit=None):
                       but the limit will be applied to the query
                       before it is executed.
 
-        :rtype: list of :class:`gcloud.datastore.entity.Entity`'s
-        :returns: The list of entities matching this query's criteria.
+        :rtype: tuple of mixed types
+        :returns: The first entry is a :class:`gcloud.datastore.entity.Entity`
+                  list matching this query's criteria. The second is a base64
+                  encoded cursor for paging and the third is a boolean
+                  indicating if there are more results.
+        :raises: `ValueError` if more_results is not one of the enums
+                 MORE_RESULTS_AFTER_LIMIT or NO_MORE_RESULTS.
         """
         clone = self
 
@@ -350,46 +364,71 @@ def fetch(self, limit=None):
         #       results. See
         #       https://github.com/GoogleCloudPlatform/gcloud-python/issues/280
         #       for discussion.
-        entity_pbs, self._cursor, self._more_results = query_results[:3]
+        entity_pbs, cursor_as_bytes, more_results_enum = query_results[:3]
 
-        return [helpers.entity_from_protobuf(entity, dataset=self.dataset())
-                for entity in entity_pbs]
+        entities = [helpers.entity_from_protobuf(entity,
+                                                 dataset=self.dataset())
+                    for entity in entity_pbs]
 
-    def cursor(self):
-        """Returns cursor ID from most recent ``fetch()``.
+        cursor = base64.b64encode(cursor_as_bytes)
 
-        .. warning:: Invoking this method on a query that has not yet
-           been executed will raise a RuntimeError.
+        if more_results_enum == self._MORE_RESULTS:
+            more_results = True
+        elif more_results_enum == self._NO_MORE_RESULTS:
+            more_results = False
+        else:
+            # Note this covers the value NOT_FINISHED since this fetch does
+            # not occur within a batch, we don't expect to see NOT_FINISHED.
+            raise ValueError('Unexpected value returned for `more_results`.')
 
-        :rtype: string
-        :returns: base64-encoded cursor ID string denoting the last position
-                  consumed in the query's result set.
-        """
-        if not self._cursor:
-            raise RuntimeError('No cursor')
-        return base64.b64encode(self._cursor)
+        return entities, cursor, more_results
 
-    def more_results(self):
-        """Returns ``more_results`` flag from most recent ``fetch()``.
+    def fetch(self, limit=None):
+        """Executes the Query and returns matching entities
 
-        .. warning:: Invoking this method on a query that has not yet
-           been executed will raise a RuntimeError.
+        This calls `fetch_page()` but does not use the paging information.
 
-        .. note::
+        For example::
+
+          >>> from gcloud import datastore
+          >>> dataset = datastore.get_dataset('dataset-id')
+          >>> query = dataset.query('Person').filter('name', '=', 'Sally')
+          >>> query.fetch()
+          [<Entity object>, <Entity object>, ...]
+          >>> query.fetch(1)
+          [<Entity object>]
+          >>> query.limit()
+          None
 
-           The `more_results` is not currently useful because it is
-           always returned by the back-end as ``MORE_RESULTS_AFTER_LIMIT``
-           even if there are no more results. See
-           https://github.com/GoogleCloudPlatform/gcloud-python/issues/280
-           for discussion.
+        :type limit: integer
+        :param limit: An optional limit to apply temporarily to this query.
+                      That is, the Query itself won't be altered,
+                      but the limit will be applied to the query
+                      before it is executed.
 
-        :rtype: :class:`gcloud.datastore.datastore_v1_pb2.
-                                QueryResultBatch.MoreResultsType`
-        :returns: enumerated value:  are there more results available.
+        :rtype: list of :class:`gcloud.datastore.entity.Entity`'s
+        :returns: The list of entities matching this query's criteria.
         """
-        if self._more_results is None:
-            raise RuntimeError('No results')
-        return self._more_results
+        entities, _, _ = self.fetch_page(limit=limit)
+        return entities
+
+    @property
+    def start_cursor(self):
+        """Property to encode start cursor bytes as base64."""
+        if not self._pb.HasField('start_cursor'):
+            return None
+
+        start_as_bytes = self._pb.start_cursor
+        return base64.b64encode(start_as_bytes)
+
+    @property
+    def end_cursor(self):
+        """Property to encode end cursor bytes as base64."""
+        if not self._pb.HasField('end_cursor'):
+            return None
+
+        end_as_bytes = self._pb.end_cursor
+        return base64.b64encode(end_as_bytes)
 
     def with_cursor(self, start_cursor, end_cursor=None):
         """Specifies the starting / ending positions in a query's result set.

gcloud/datastore/test_connection.py

@@ -449,8 +449,13 @@ def test_run_query_wo_namespace_empty_result(self):
 
         DATASET_ID = 'DATASET'
         KIND = 'Nonesuch'
+        CURSOR = b'\x00'
         q_pb = Query(KIND, DATASET_ID).to_protobuf()
         rsp_pb = datastore_pb.RunQueryResponse()
+        rsp_pb.batch.end_cursor = CURSOR
+        no_more = datastore_pb.QueryResultBatch.NO_MORE_RESULTS
+        rsp_pb.batch.more_results = no_more
+        rsp_pb.batch.entity_result_type = datastore_pb.EntityResult.FULL
         conn = self._makeOne()
         URI = '/'.join([
             conn.API_BASE_URL,
@@ -463,7 +468,7 @@ def test_run_query_wo_namespace_empty_result(self):
         http = conn._http = Http({'status': '200'}, rsp_pb.SerializeToString())
         pbs, end, more, skipped = conn.run_query(DATASET_ID, q_pb)
         self.assertEqual(pbs, [])
-        self.assertEqual(end, '')
+        self.assertEqual(end, CURSOR)
         self.assertTrue(more)
         self.assertEqual(skipped, 0)
         cw = http._called_with