simplest: instance_eval

Rakefile

@@ -5,5 +5,5 @@ require "yard/rake/yardoc_task"
 YARD::Rake::YardocTask.new do |t|
   OTHER_PATHS = %w(README.md LICENSE)
   t.files   = ['lib/**/*.rb', OTHER_PATHS]
-  t.options = ['--main README.md']
+  t.options = ['--main', 'README.md']
 end

lib/docile.rb

@@ -1,5 +1,23 @@
 require "docile/version"
 
 module Docile
-  # Your code goes here...
+  # Executes a block in the context of an object whose interface represents a DSL.
+  #
+  #   Docile.dsl_eval([]) do
+  #     push 1
+  #     push 2
+  #     pop
+  #     push 3
+  #   end
+  #   #=> [1, 3]
+  #
+  # @param dsl [Object]  an object whose methods represent a DSL
+  # @param block [Proc]  a block to execute in the DSL context
+  # @return [Object]     the given DSL object
+  def dsl_eval(dsl, &block)
+    block_context = eval("self", block.binding)
+    dsl.instance_eval(&block)
+    dsl
+  end
+  module_function :dsl_eval
 end

spec/docile_spec.rb

@@ -0,0 +1,75 @@
+require "spec_helper"
+
+describe Docile do
+
+  context :dsl_eval do
+
+    class InnerDSL
+      def initialize; @b = 'b'; end
+      attr_accessor :b
+    end
+
+    class OuterDSL
+      def initialize; @a = 'a'; end
+      attr_accessor :a
+      def inner(&block)
+        Docile.dsl_eval(InnerDSL.new, &block)
+      end
+    end
+
+    def outer(&block)
+      Docile.dsl_eval(OuterDSL.new, &block)
+    end
+
+    it "should return the DSL object" do
+      Docile.dsl_eval([]) do
+        push 1
+        push 2
+        pop
+        push 3
+      end.should == [1, 3]
+    end
+
+    context "methods"
+
+      it "should find method of outer dsl in outer dsl scope" do
+        outer { a.should == 'a' }
+      end
+
+      it "should find method of inner dsl in inner dsl scope" do
+        outer { inner { b.should == 'b' } }
+      end
+
+      #it "should find method of outer dsl in inner dsl scope" do
+      #  outer { inner { a.should == 'a' } }
+      #end
+      #
+      #it "should find method of block's context in outer dsl scope" do
+      #  def c; 'c'; end
+      #  outer { c.should == 'c' }
+      #end
+      #
+      #it "should find method of block's context in inner dsl scope" do
+      #  def c; 'c'; end
+      #  outer { inner { c.should == 'c' } }
+      #end
+    end
+
+  #  it "should find local variable from block context in outer dsl scope" do
+  #    foo = 'foo'
+  #    outer { foo.should == 'foo' }
+  #  end
+  #
+  #
+  #
+  #  it "should find local variable from block definition in inner dsl scope" do
+  #    bar = 'bar'
+  #    outer { inner { bar.should == 'bar' } }
+  #  end
+  #
+  #  it "should find instance variable from block definition in inner dsl scope" do
+  #    @iv1 = 'iv1'; outer { inner { @iv1.should == 'iv1' } }
+  #  end
+  #end
+
+end

spec/spec_helper.rb

@@ -0,0 +1,10 @@
+require 'rubygems'
+require 'rspec'
+
+test_dir = File.dirname(__FILE__)
+$LOAD_PATH.unshift test_dir unless $LOAD_PATH.include?(test_dir)
+
+lib_dir = File.join(File.dirname(test_dir), 'lib')
+$LOAD_PATH.unshift lib_dir unless $LOAD_PATH.include?(lib_dir)
+
+require 'docile'