Allow rackup .rb files by getting a conventionally named constant as the app

This is written per spec in the rackup binary

Author: bmizerany

example/myapp.rb

@@ -0,0 +1 @@
+Myapp = lambda { |env| [200, {}, 'this is my app!'] }

lib/thin/controllers/controller.rb

@@ -161,8 +161,16 @@ def load_adapter
         end
 
         def load_rackup_config
-          rackup_code = File.read(@options[:rackup])
-          eval("Rack::Builder.new {( #{rackup_code}\n )}.to_app", TOPLEVEL_BINDING, @options[:rackup])
+          case @options[:rackup]
+          when /\.rb$/
+            Kernel.load(@options[:rackup])
+            Object.const_get(File.basename(@options[:rackup], '.rb').capitalize.to_sym)
+          when /\.ru$/
+            rackup_code = File.read(@options[:rackup])
+            eval("Rack::Builder.new {( #{rackup_code}\n )}.to_app", TOPLEVEL_BINDING, @options[:rackup])
+          else
+            raise "Invalid rackup file.  please specify either a .ru or .rb file"
+          end
         end
     end
   end

spec/controllers/controller_spec.rb

@@ -63,18 +63,33 @@
   end
 
   it "should load app from Rack config" do
-    @controller.options[:rackup] = 'example/config.ru'    
+    @controller.options[:rackup] = File.dirname(__FILE__) + '/../../example/config.ru'    
     @controller.start
 
     @server.app.class.should == Proc
   end
+
+  it "should load app from ruby file" do
+    @controller.options[:rackup] = filename = File.dirname(__FILE__) + '/../../example/myapp.rb'    
+    @controller.start
+    
+    @server.app.should == Myapp
+  end
+
+  it "should throwup if rackup is not a .ru or .rb file" do
+    proc do
+      @controller.options[:rackup] = filename = File.dirname(__FILE__) + '/../../example/myapp.foo'    
+      @controller.start
+    end.should raise_error(RuntimeError, /please/)
+  end
 
   it "should set server as threaded" do
     @controller.options[:threaded] = true
     @controller.start
 
     @server.threaded.should be_true
   end
+    
 end
 
 describe Controller do