support instance variables from block context in multi-level dsl

lib/docile.rb

@@ -15,12 +15,12 @@ module Docile
   #
   # @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
+  # @return    [Object]  the dsl object, after execution of the block
   def dsl_eval(dsl, &block)
     block_context = eval("self", block.binding)
     proxy_context = FallbackContextProxy.new(dsl, block_context)
-    block_context.instance_variables.each { |ivar| proxy_context.instance_variable_set(ivar, block_context.instance_variable_get(ivar)) }
     begin
+      block_context.instance_variables.each { |ivar| proxy_context.instance_variable_set(ivar, block_context.instance_variable_get(ivar)) }
       proxy_context.instance_eval(&block)
     ensure
       block_context.instance_variables.each { |ivar| block_context.instance_variable_set(ivar, proxy_context.instance_variable_get(ivar)) }

lib/docile/fallback_context_proxy.rb

@@ -2,12 +2,14 @@ require 'set'
 
 module Docile
   class FallbackContextProxy
-    BASIC_METHODS = Set[:==, :equal?, :"!", :"!=",
-                        :instance_eval, :instance_variable_get, :instance_variable_set,
-                        :object_id, :__send__, :__id__]
+    NON_PROXIED_METHODS = Set[:object_id, :__send__, :__id__, :==, :equal?, :"!", :"!=", :instance_eval,
+                              :instance_variables, :instance_variable_get, :instance_variable_set,
+                              :remove_instance_variable]
+
+    NON_PROXIED_INSTANCE_VARIABLES = Set[:@__receiver__, :@__fallback__]
 
     instance_methods.each do |method|
-      unless BASIC_METHODS.include?(method.to_sym)
+      unless NON_PROXIED_METHODS.include?(method.to_sym)
         undef_method(method)
       end
     end
@@ -26,6 +28,11 @@ module Docile
       __proxy_method__(:sub, *args, &block)
     end
 
+    # Special case to allow proxy instance variables
+    def instance_variables
+      super - NON_PROXIED_INSTANCE_VARIABLES.to_a
+    end
+
     def method_missing(method, *args, &block)
       __proxy_method__(method, *args, &block)
     end

spec/docile_spec.rb

@@ -76,11 +76,17 @@ describe Docile do
         @iv1 = 'iv1'; outer { @iv1.should == 'iv1' }
       end
 
-      #it "should find instance variable from block definition in inner dsl scope" do
-      #  @iv2 = 'iv2'; outer { inner {
-      #    @iv2.should == 'iv2'
-      #  } }
-      #end
+      it "should write instance variable assigned in block into outer dsl scope" do
+        @iv1 = 'foo'; outer { @iv1 = 'bar' }; @iv1.should == 'bar'
+      end
+
+      it "should find instance variable from block definition in inner dsl scope" do
+        @iv2 = 'iv2'; outer { inner { @iv2.should == 'iv2' } }
+      end
+
+      it "should find instance variable from block definition in inner dsl scope" do
+        @iv2 = 'foo'; outer { inner { @iv2 = 'bar' } }; @iv2.should == 'bar'
+      end
     end
 
   end