If ec2 filtering exclude all instances for a reservation, remove the reservation from the results.

moto/ec2/utils.py

@@ -98,10 +98,13 @@ def passes_filter_dict(instance, filter_dict):
 
 
 def filter_reservations(reservations, filter_dict):
+    result = []
     for reservation in reservations:
         new_instances = []
         for instance in reservation.instances:
             if passes_filter_dict(instance, filter_dict):
                 new_instances.append(instance)
-        reservation.instances = new_instances
-    return reservations
+        if new_instances:
+            reservation.instances = new_instances
+            result.append(reservation)
+    return result

tests/test_ec2/test_instances.py

@@ -96,6 +96,9 @@ def test_get_instances_filtering_by_state():
     instance_ids = [instance.id for instance in reservations[0].instances]
     instance_ids.should.equal([instance2.id])
 
+    reservations = conn.get_all_instances([instance2.id], filters={'instance-state-name': 'terminating'})
+    list(reservations).should.equal([])
+
     # get_all_instances should still return all 3
     reservations = conn.get_all_instances()
     reservations[0].instances.should.have.length_of(3)