fix sorted set when for non existent key

from: guilleiguaran#95

lib/redis/connection/memory.rb

@@ -900,6 +900,17 @@ def zremrangebyscore(key, min, max)
         range.size
       end
 
+      def zremrangebyrank(key, start, stop)
+        data_type_check(key, ZSet)
+        return 0 unless data[key]
+
+        sorted_elements = data[key].sort_by { |k, v| v }
+        start = sorted_elements.length if start > sorted_elements.length
+        elements_to_delete = sorted_elements[start..stop]
+        elements_to_delete.each { |elem, rank| data[key].delete(elem) }
+        elements_to_delete.size
+      end
+
       def zinterstore(out, *args)
         data_type_check(out, ZSet)
         args_handler = SortedSetArgumentHandler.new(args)
@@ -914,14 +925,6 @@ def zunionstore(out, *args)
         data[out].size
       end
 
-      def zremrangebyrank(key, start, stop)
-        sorted_elements = data[key].sort_by { |k, v| v }
-        start = sorted_elements.length if start > sorted_elements.length
-        elements_to_delete = sorted_elements[start..stop]
-        elements_to_delete.each { |elem, rank| data[key].delete(elem) }
-        elements_to_delete.size
-      end
-
       private
         def raise_argument_error(command, match_string=command)
           error_message = if %w(hmset mset_odd).include?(match_string.downcase)

spec/sorted_sets_spec.rb

@@ -333,6 +333,10 @@ module FakeRedis
         @client.zremrangebyrank("key", 25, -1).should be == 0
         @client.zcard('key').should be == 3
       end
+
+      it "should return 0 if the key didn't exist" do
+        @client.zremrangebyrank("key", 0, 1).should be == 0
+      end
     end
 
     describe "#zunionstore" do