Detach before executing callbacks.

This allows to make queries in callbacks.

lib/mysql2/em.rb

@@ -13,12 +13,12 @@ module Mysql2
         end
 
         def notify_readable
+          detach
           begin
             @deferable.succeed(@client.async_result)
           rescue Exception => e
             @deferable.fail(e)
           end
-          detach
         end
       end
 

spec/em/em_spec.rb

@@ -23,4 +23,23 @@ describe Mysql2::EM::Client do
     results[0].keys.should include("second_query")
     results[1].keys.should include("first_query")
   end
+
+  it "should support queries in callbacks" do
+    results = []
+    EM.run do
+      client = Mysql2::EM::Client.new
+      defer1 = client.query "SELECT sleep(0.025) as first_query"
+      defer1.callback do |result|
+        results << result.first
+        defer2 = client.query "SELECT sleep(0.025) as second_query"
+        defer2.callback do |result|
+          results << result.first
+          EM.stop_event_loop
+        end
+      end
+    end
+
+    results[0].keys.should include("first_query")
+    results[1].keys.should include("second_query")
+  end
 end