Added application inclusion

examples/plugins/config.ru

@@ -0,0 +1,10 @@
+# frozen_string_literal: true
+
+$LOAD_PATH.unshift("#{File.dirname(__FILE__)}/lib")
+require 'hyde'
+
+app = Hyde::Server.new do
+  plugin "helloworld.ru"
+end
+
+run app

examples/plugins/helloworld.ru

@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+$LOAD_PATH.unshift("#{File.dirname(__FILE__)}/lib")
+require 'hyde'
+
+app = Hyde::Server.new do
+  get "/hello" do
+    header "content-type", "text/plain"
+    "Hello World!"
+  end
+end
+
+run app

examples/plugins/lib

@@ -0,0 +1 @@
+../../lib

lib/hyde/dsl/methods_path.rb

@@ -56,6 +56,20 @@ module Hyde
         @origin.filter(&block)
         block
       end
+
+      # Include an application as a child of path.
+      # @param filename [String]
+      def plugin(filename)
+        self.define_singleton_method(:run) do |object|
+          unless object.is_a? Hyde::Node
+            raise StandardError, "not a node instance or subclass instance"
+          end
+
+          object
+        end
+        @origin.children.append(self.instance_eval(File.read(filename)))
+        self.singleton_class.undef_method :run
+      end
     end
   end
 end