Return the expression source instead of nil (#116)

Author: svenwin

ruby/lib/cucumber/cucumber_expressions/cucumber_expression.rb

@@ -32,7 +32,7 @@ def regexp
       end
 
       def to_s
-        @source.inspect
+        source.inspect
       end
 
       private

ruby/spec/cucumber/cucumber_expressions/cucumber_expression_spec.rb

@@ -95,6 +95,11 @@ module CucumberExpressions
         expect(CucumberExpression.new(expr, ParameterTypeRegistry.new).source).to eq(expr)
       end
 
+      it "exposes source via #to_s" do
+        expr = "I have {int} cuke(s)"
+        expect(CucumberExpression.new(expr, ParameterTypeRegistry.new).to_s).to eq(expr.inspect)
+      end
+
       it "unmatched optional groups have undefined values" do
         parameter_type_registry = ParameterTypeRegistry.new
         parameter_type_registry.define_parameter_type(