started on the pretty print functions

Language/Gherkin.hs

@@ -2,8 +2,10 @@ module Language.Gherkin
        (
          module Language.Gherkin.AST
        , module Language.Gherkin.Parser
+       , module Language.Gherkin.Pretty
        )
        where
 
 import Language.Gherkin.AST
 import Language.Gherkin.Parser
+import Language.Gherkin.Pretty

Language/Gherkin/Pretty.hs

@@ -0,0 +1,16 @@
+{-# LANGUAGE NamedFieldPuns #-}
+
+module Language.Gherkin.Pretty where
+
+import Language.Gherkin.AST
+import Text.PrettyPrint
+
+pretty :: Feature -> Doc
+pretty Feature { -- feature_tags
+               feature_name
+               , feature_description
+               -- , feature_background
+               -- , feature_scenarios
+               } = text "Feature:" <+> text feature_name $$ nest 4 featureBody
+  where
+    featureBody = text feature_description

gherkin.cabal

@@ -22,6 +22,7 @@ test-suite test
     QuickCheck >= 2.4.0.0,
     parsec >= 3.1.1,
     gherkin >= 0.1,
+    pretty >= 1.0.2.1,
     MissingH >= 1.1.0.3
 
 Library
@@ -30,10 +31,12 @@ Library
   exposed-modules: 
     Language.Gherkin, 
     Language.Gherkin.AST,
-    Language.Gherkin.Parser       
+    Language.Gherkin.Parser,
+    Language.Gherkin.Pretty
   build-depends:
     base >= 4,
-    parsec >= 3.1.1
+    parsec >= 3.1.1,
+    pretty >= 1.0.2.1
 
   -- Modules not exported by this package.
   -- Other-modules:       

tests/Instances.hs

@@ -0,0 +1,15 @@
+module Instances where
+import Test.QuickCheck
+import Language.Gherkin
+
+newtype GF = GF Feature
+             deriving (Eq, Show)
+
+instance Arbitrary GF where
+  arbitrary = return $ GF $ Feature {
+    feature_tags = []
+    , feature_name = "feature"
+    , feature_description = "description"
+    , feature_background = Nothing
+    , feature_scenarios = []
+    }

tests/Main.hs

@@ -4,10 +4,14 @@ import Test.Framework
 import Test.Framework.Providers.QuickCheck2
 import Text.Parsec
 import Text.Parsec.String
+import Instances
 import Language.Gherkin
+import Text.PrettyPrint
 
 main :: IO ()
-main = defaultMain [testGroup "Parsing tests" tests]
+main = defaultMain [testGroup "Parsing tests" tests
+                   , testGroup "Pretty roundtrip" prettyTests 
+                   ]
 
 feature :: Feature
 feature = Feature { feature_tags = []
@@ -26,6 +30,13 @@ prop p str = case parse p "" str of
 l =.= r | l /= r = error $ "Expected '"  ++ show r ++ "'\nGot '" ++ show l
         | otherwise = True
 
+
+prettyTests :: [Test]
+prettyTests = [
+  testProperty "" $ \(GF f) ->
+   prop parseFeature (render $ pretty f) =.= f
+  ]
+
 tests :: [Test]
 tests = [
   testProperty "parse table" $