Try not to register the exact same measuring method twice

Author: aycabta

lib/irb/cmd/measure.rb

@@ -20,11 +20,11 @@ def execute(type = nil, arg = nil)
         when :on
           IRB.conf[:MEASURE] = true
           added = IRB.set_measure_callback(type, arg)
-          puts "#{added[0]} is added."
+          puts "#{added[0]} is added." if added
         else
           IRB.conf[:MEASURE] = true
           added = IRB.set_measure_callback(type, arg)
-          puts "#{added[0]} is added."
+          puts "#{added[0]} is added." if added
         end
         nil
       end

lib/irb/init.rb

@@ -158,8 +158,18 @@ def IRB.set_measure_callback(type = nil, arg = nil)
     else
       added = [:TIME, IRB.conf[:MEASURE_PROC][:TIME], arg]
     end
-    IRB.conf[:MEASURE_CALLBACKS] << added if added
-    added
+    if added
+      found = IRB.conf[:MEASURE_CALLBACKS].find{ |m| m[0] == added[0] && m[2] == added[2] }
+      if found
+        # already added
+        nil
+      else
+        IRB.conf[:MEASURE_CALLBACKS] << added if added
+        added
+      end
+    else
+      nil
+    end
   end
 
   def IRB.unset_measure_callback(type = nil)