From 4168abcf1ed6cc23649853f1438f61ad6333414f Mon Sep 17 00:00:00 2001
From: Justin George <justin.george@gmail.com>
Date: Thu, 13 May 2010 14:07:40 -0700
Subject: [PATCH] add start event api to allow instrumentation of start events framework-wide [#4594 state:resolved]

Useful for places where we care about when things start more than how long they take
---
 activesupport/lib/active_support/notifications.rb  |    2 +-
 .../active_support/notifications/instrumenter.rb   |   11 +++++
 activesupport/test/notifications_test.rb           |   41 +++++++++++++++++++-
 3 files changed, 52 insertions(+), 2 deletions(-)

diff --git a/activesupport/lib/active_support/notifications.rb b/activesupport/lib/active_support/notifications.rb
index 3f1fe64..5448b9f 100644
--- a/activesupport/lib/active_support/notifications.rb
+++ b/activesupport/lib/active_support/notifications.rb
@@ -45,7 +45,7 @@ module ActiveSupport
     class << self
       attr_writer :notifier
       delegate :publish, :subscribe, :unsubscribe, :to => :notifier
-      delegate :instrument, :to => :instrumenter
+      delegate :instrument, :instrument_with_start, :to => :instrumenter
 
       def notifier
         @notifier ||= Notifier.new
diff --git a/activesupport/lib/active_support/notifications/instrumenter.rb b/activesupport/lib/active_support/notifications/instrumenter.rb
index 7e89402..3d40852 100644
--- a/activesupport/lib/active_support/notifications/instrumenter.rb
+++ b/activesupport/lib/active_support/notifications/instrumenter.rb
@@ -26,6 +26,17 @@ module ActiveSupport
         end
       end
 
+      def instrument_with_start(name, payload={})
+        if block_given?
+          instrument("#{name}.start", payload.dup)
+          instrument(name, payload) do
+            yield(payload)
+          end
+        else
+          instrument(name, payload)
+        end
+      end
+
       private
         def unique_id
           SecureRandom.hex(10)
diff --git a/activesupport/test/notifications_test.rb b/activesupport/test/notifications_test.rb
index e11de5f..277a49e 100644
--- a/activesupport/test/notifications_test.rb
+++ b/activesupport/test/notifications_test.rb
@@ -127,6 +127,45 @@ module Notifications
       end
   end
 
+  class InstrumentWithStartTest < TestCase
+    delegate :instrument_with_start, :to => ActiveSupport::Notifications
+
+    def test_instrument_with_start_returns_block_result
+      assert_equal 4, instrument_with_start(:even_better) { 2 + 2 }
+    end
+
+    def test_instrument_with_start_creates_one_event_with_no_block
+      instrument_with_start(:do_stuff_man)
+      drain
+      assert_equal 1, @events.size
+      assert_equal :do_stuff_man, @events.first.name
+    end
+
+    def test_instrument_with_start_creates_two_events_when_given_block
+      instrument_with_start(:do_stuff_man) { nil }
+      drain
+      assert_equal 2, @events.size
+    end
+
+    def test_instrument_with_start_uses_correct_start_event_name
+      instrument_with_start(:do_stuff_man) { nil }
+      drain
+      assert_equal 2, @events.size
+      assert_equal 'do_stuff_man.start', @events.first.name
+    end
+
+    def test_instrument_with_start_yields_payload_to_second_notification
+      assert_equal 4, instrument_with_start(:even_better) { |p| p[:result] = 2 + 2 }
+      drain
+
+      assert_equal 2, @events.size
+      assert_equal :even_better, @events.last.name
+      assert_equal Hash[:result => 4], @events.last.payload
+    end
+
+  end
+
+
   class InstrumentationTest < TestCase
     delegate :instrument, :to => ActiveSupport::Notifications
 
@@ -135,7 +174,7 @@ module Notifications
       drain
     end
 
-    def test_instrument_yields_the_paylod_for_further_modification
+    def test_instrument_yields_payload_for_further_modification
       assert_equal 2, instrument(:awesome) { |p| p[:result] = 1 + 1 }
       drain
 
-- 
1.7.0.3