Use JSON.pretty_generate

mrblib/rf/00filter/json.rb

@@ -24,7 +24,7 @@ def decorate(val)
         if raw? && val.instance_of?(String)
           val
         else
-          JSON.pretty_generate(val)
+          val.to_json
         end
       end
     end

mrblib/rf/features.rb

@@ -49,5 +49,11 @@ def add_features_to_hash
         key?(sym.to_s) || super
       end
     end
+
+    def add_features_to_json
+      Object.define_method(:to_json) do
+        JSON.pretty_generate(self)
+      end
+    end
   end
 end

mrblib/rf/runner.rb

@@ -37,6 +37,7 @@ def add_features
       Rf.add_features_to_integer
       Rf.add_features_to_float
       Rf.add_features_to_hash
+      Rf.add_features_to_json
     end
 
     def do_action

spec/feature_spec.rb

@@ -96,4 +96,14 @@
       it { expect(last_command_started).to have_output output_string_eq output }
     end
   end
+
+  describe 'to_json' do
+    let(:input) { load_fixture('json/hash.json') }
+    let(:output) do
+      before { run_rf("-j -q 'puts _.to_json'", input) }
+
+      it { expect(last_command_started).to be_successfully_executed }
+      it { expect(last_command_started).to have_output output_string_eq output }
+    end
+  end
 end