Don't encode controls as block strings

Fixes #39.

String containing control sequences should be encoded as simple strings
even if they contain newlines, since the block strings can contain only
SourceCharacters.

tests/Language/GraphQL/AST/EncoderSpec.hs

@@ -6,8 +6,10 @@ module Language.GraphQL.AST.EncoderSpec
 
 import Language.GraphQL.AST
 import Language.GraphQL.AST.Encoder
-import Test.Hspec (Spec, context, describe, it, shouldBe)
+import Test.Hspec (Spec, context, describe, it, shouldBe, shouldStartWith, shouldEndWith, shouldNotContain)
+import Test.QuickCheck (choose, oneof, forAll)
 import Text.RawString.QQ (r)
+import Data.Text.Lazy (cons, toStrict, unpack)
 
 spec :: Spec
 spec = do
@@ -20,21 +22,102 @@ spec = do
         context "minified" $ do
             it "escapes \\" $
                 value minified (String "\\") `shouldBe` "\"\\\\\""
-            it "escapes quotes" $
+            it "escapes double quotes" $
                 value minified (String "\"") `shouldBe` "\"\\\"\""
+            it "escapes \\f" $
+                value minified (String "\f") `shouldBe` "\"\\f\""
+            it "escapes \\n" $
+                value minified (String "\n") `shouldBe` "\"\\n\""
+            it "escapes \\r" $
+                value minified (String "\r") `shouldBe` "\"\\r\""
+            it "escapes \\t" $
+                value minified (String "\t") `shouldBe` "\"\\t\""
             it "escapes backspace" $
                 value minified (String "a\bc") `shouldBe` "\"a\\bc\""
-            it "escapes Unicode" $
-                value minified (String "\0") `shouldBe` "\"\\u0000\""
+            context "escapes Unicode for chars less than 0010" $ do
+                it "Null" $ value minified (String "\x0000") `shouldBe` "\"\\u0000\""
+                it "bell" $ value minified (String "\x0007") `shouldBe` "\"\\u0007\""
+            context "escapes Unicode for char less than 0020" $ do
+                it "DLE" $ value minified (String "\x0010") `shouldBe` "\"\\u0010\""
+                it "EM" $ value minified (String "\x0019") `shouldBe` "\"\\u0019\""
+            context "encodes without escape" $ do
+                it "space" $ value minified (String "\x0020") `shouldBe` "\" \""
+                it "~" $ value minified (String "\x007E") `shouldBe` "\"~\""
 
         context "pretty" $ do
             it "uses strings for short string values" $
                 value pretty (String "Short text") `shouldBe` "\"Short text\""
-            it "uses block strings for text with new lines" $
+            it "uses block strings for text with new lines, with newline symbol" $
                 value pretty (String "Line 1\nLine 2")
-                    `shouldBe` "\"\"\"\n  Line 1\n  Line 2\n\"\"\""
-            it "escapes \\ in short strings" $
-                value pretty (String "\\") `shouldBe` "\"\\\\\""
+                    `shouldBe` [r|"""
+  Line 1
+  Line 2
+"""|]
+            it "uses block strings for text with new lines, with CR symbol" $
+                value pretty (String "Line 1\rLine 2")
+                    `shouldBe` [r|"""
+  Line 1
+  Line 2
+"""|]
+            it "uses block strings for text with new lines, with CR symbol followed by newline" $
+                value pretty (String "Line 1\r\nLine 2")
+                    `shouldBe` [r|"""
+  Line 1
+  Line 2
+"""|]
+            it "encodes as one line string if has escaped symbols" $ do
+                let
+                  genNotAllowedSymbol = oneof
+                    [ choose ('\x0000', '\x0008')
+                    , choose ('\x000B', '\x000C')
+                    , choose ('\x000E', '\x001F')
+                    , pure '\x007F'
+                    ]
+
+                forAll genNotAllowedSymbol $ \x -> do
+                    let
+                      rawValue = "Short \n" <> cons x "text"
+                      encoded = value pretty (String $ toStrict rawValue)
+                    shouldStartWith (unpack encoded) "\""
+                    shouldEndWith (unpack encoded) "\""
+                    shouldNotContain (unpack encoded) "\"\"\""
+
+            it "Hello world" $ value pretty (String "Hello,\n  World!\n\nYours,\n  GraphQL.")
+              `shouldBe` [r|"""
+  Hello,
+    World!
+
+  Yours,
+    GraphQL.
+"""|]
+
+            it "has only newlines" $ value pretty (String "\n") `shouldBe` [r|"""
+
+
+"""|]
+            it "has newlines and one symbol at the begining" $
+              value pretty (String "a\n\n") `shouldBe` [r|"""
+  a
+
+
+"""|]
+            it "has newlines and one symbol at the end" $
+              value pretty (String "\n\na") `shouldBe` [r|"""
+
+
+  a
+"""|]
+            it "has newlines and one symbol in the middle" $
+              value pretty (String "\na\n") `shouldBe` [r|"""
+
+  a
+
+"""|]
+            it "skip trailing whitespaces" $ value pretty (String "  Short\ntext    ")
+              `shouldBe` [r|"""
+  Short
+  text
+"""|]
 
     describe "definition" $
         it "indents block strings in arguments" $