Fix PlainBackend about to use top-level include

[Fix GH-303]

Author: mrkn

lib/iruby/backend.rb

@@ -40,6 +40,7 @@ def initialize
       require 'irb/completion'
       IRB.setup(nil)
       @main = TOPLEVEL_BINDING.eval("self").dup
+      init_main_object(@main)
       @workspace = IRB::WorkSpace.new(@main)
       @irb = IRB::Irb.new(@workspace)
       @eval_path = @irb.context.irb_path
@@ -58,6 +59,16 @@ def eval(code, store_history)
     def complete(code)
       IRB::InputCompletor::CompletionProc.call(code)
     end
+
+    private
+
+    def init_main_object(main)
+      wrapper_module = Module.new
+      main.extend(wrapper_module)
+      main.define_singleton_method(:include) do |mod|
+        wrapper_module.include(mod)
+      end
+    end
   end
 
   class PryBackend

test/iruby/backend_test.rb

@@ -8,6 +8,12 @@ def test_eval_one_plus_two
       assert_equal 3, @plainbackend.eval('1+2', false)
     end
 
+    def test_include_module
+      assert_nothing_raised do
+        @plainbackend.eval("include Math", false)
+      end
+    end
+
     def test_complete_req
       assert_includes @plainbackend.complete('req'), 'require'
     end
@@ -26,6 +32,12 @@ def test_eval_one_plus_two
       assert_equal 3, @prybackend.eval('1+2', false)
     end
 
+    def test_include_module
+      assert_nothing_raised do
+        @prybackend.eval("include Math", false)
+      end
+    end
+
     def test_complete_req
       assert_includes @prybackend.complete('req'), 'require'
     end