Completion for instance and class variables.

Pry is now able to complete variable names for instance and class variables, as
well as being able to complete methods and the like on these variables.

Signed-off-by: Yorick Peterse <yorickpeterse@gmail.com>

lib/pry/completion.rb

@@ -180,7 +180,15 @@ class Pry
           select_message(receiver, message, candidates)
 
         else
-          candidates = eval("methods | private_methods | local_variables | self.class.constants", bind).collect{|m| m.to_s}
+          candidates = eval(
+            "methods | private_methods | local_variables | " \
+              "self.class.constants | instance_variables",
+            bind
+          ).collect{|m| m.to_s}
+
+          if eval("respond_to?(:class_variables)", bind)
+            candidates += eval("class_variables", bind).collect { |m| m.to_s }
+          end
 
           (candidates|ReservedWords|commands).grep(/^#{Regexp.quote(input)}/)
         end

test/test_completion.rb

@@ -22,5 +22,31 @@ describe Pry::InputCompleter do
       lambda{ completer.call "a.to_s." }.should.not.raise Exception
     end
   end
+
+  it 'should complete instance variables' do
+    object = Object.new
+
+    object.instance_variable_set(:'@name', 'Pry')
+    object.class.class_variable_set(:'@@number', 10)
+
+    object.instance_variables.include?(:'@name').should       == true
+    object.class.class_variables.include?(:'@@number').should == true
+
+    completer = Pry::InputCompleter.build_completion_proc(
+      Pry.binding_for(object)
+    )
+
+    # Complete instance variables.
+    completer.call('@na').include?('@name').should                 == true
+    completer.call('@name.down').include?('@name.downcase').should == true
+
+    # Complete class variables.
+    completer = Pry::InputCompleter.build_completion_proc(
+      Pry.binding_for(object.class)
+    )
+
+    completer.call('@@nu').include?('@@number').should              == true
+    completer.call('@@number.cl').include?('@@number.class').should == true
+  end
 end