adding Enlighten::Trigger exception which records caller binding

lib/enlighten.rb

@@ -1 +1,2 @@
-require "enlighten/middleware"
+require "enlighten/middleware"
+require "enlighten/trigger"

lib/enlighten/trigger.rb

@@ -0,0 +1,23 @@
+module Enlighten
+  class Trigger < Exception
+    attr_reader :binding_of_caller
+
+    # From: http://stackoverflow.com/questions/106920/how-can-i-get-source-and-variable-values-in-ruby-tracebacks
+    def initialize
+      expected_file, expected_line = caller(1).first.split(':')[0,2]
+      expected_line = expected_line.to_i
+      return_count = 5
+
+      set_trace_func(proc do |event, file, line, id, binding, kls|
+        if file == expected_file && line == expected_line
+          @binding_of_caller = binding
+          set_trace_func(nil)
+        end
+
+        if event == :return
+          set_trace_func(nil) if (return_count -= 1) <= 0
+        end
+      end)
+    end
+  end
+end

spec/enlighten/trigger_spec.rb

@@ -0,0 +1,16 @@
+require "spec_helper"
+
+describe Enlighten::Trigger do
+  def trigger
+    something = "foo"
+    raise Enlighten::Trigger
+  end
+
+  it "should contain caller's binding" do
+    begin
+      trigger
+    rescue Enlighten::Trigger => e
+      eval("something", e.binding_of_caller).should == "foo"
+    end
+  end
+end