Merge pull request #873 from haskell/double-serialize

Change +inf/-inf :: Double/Float serialization

Author: phadej

changelog.md

@@ -15,6 +15,9 @@ For the latest version of this document, please see [https://github.com/haskell/
 
 * Remove Data.Aeson.Encode module
 
+* `Double` and `Float` infinities are encoded as `"+inf"` and `"-inf"`.
+  Change `To/FromJSONKey` instances to use `"+inf"` and `"-inf"` too.
+
 ### 1.5.6.0
 * Make `Show Value` instance print object keys in lexicographic order.
 

src/Data/Aeson/Encoding/Internal.hs

@@ -294,6 +294,20 @@ integer = Encoding . B.integerDec
 float :: Float -> Encoding
 float = realFloatToEncoding $ Encoding . B.floatDec
 
+-- |
+--
+-- >>> double 42
+-- "42.0"
+--
+-- >>> double (0/0)
+-- "null"
+--
+-- >>> double (1/0)
+-- "\"+inf\""
+--
+-- >>> double (-23/0)
+-- "\"-inf\""
+--
 double :: Double -> Encoding
 double = realFloatToEncoding $ Encoding . B.doubleDec
 
@@ -302,8 +316,9 @@ scientific = Encoding . EB.scientific
 
 realFloatToEncoding :: RealFloat a => (a -> Encoding) -> a -> Encoding
 realFloatToEncoding e d
-    | isNaN d || isInfinite d = null_
-    | otherwise               = e d
+    | isNaN d      = null_
+    | isInfinite d = if d > 0 then Encoding "\"+inf\"" else Encoding "\"-inf\""
+    | otherwise    = e d
 {-# INLINE realFloatToEncoding #-}
 
 -------------------------------------------------------------------------------
@@ -344,10 +359,28 @@ integerText :: Integer -> Encoding' a
 integerText = Encoding . EB.quote . B.integerDec
 
 floatText :: Float -> Encoding' a
-floatText = Encoding . EB.quote . B.floatDec
+floatText d
+    | isInfinite d = if d > 0 then Encoding "\"+inf\"" else Encoding "\"-inf\""
+    | otherwise = Encoding . EB.quote . B.floatDec $ d
 
+-- |
+--
+-- >>> doubleText 42
+-- "\"42.0\""
+--
+-- >>> doubleText (0/0)
+-- "\"NaN\""
+--
+-- >>> doubleText (1/0)
+-- "\"+inf\""
+--
+-- >>> doubleText (-23/0)
+-- "\"-inf\""
+--
 doubleText :: Double -> Encoding' a
-doubleText = Encoding . EB.quote . B.doubleDec
+doubleText d
+    | isInfinite d = if d > 0 then Encoding "\"+inf\"" else Encoding "\"-inf\""
+    | otherwise = Encoding . EB.quote . B.doubleDec $ d
 
 scientificText :: Scientific -> Encoding' a
 scientificText = Encoding . EB.quote . EB.scientific

src/Data/Aeson/Types/FromJSON.hs

@@ -178,9 +178,11 @@ parseJSONElemAtIndex :: (Value -> Parser a) -> Int -> V.Vector Value -> Parser a
 parseJSONElemAtIndex p idx ary = p (V.unsafeIndex ary idx) <?> Index idx
 
 parseRealFloat :: RealFloat a => String -> Value -> Parser a
-parseRealFloat _    (Number s) = pure $ Scientific.toRealFloat s
-parseRealFloat _    Null       = pure (0/0)
-parseRealFloat name v          = prependContext name (unexpected v)
+parseRealFloat _    (Number s)      = pure $ Scientific.toRealFloat s
+parseRealFloat _    Null            = pure (0/0)
+parseRealFloat _    (String "-inf") = pure (negate 1/0)
+parseRealFloat _    (String "+inf") = pure (1/0)
+parseRealFloat name v               = prependContext name (unexpected v)
 
 parseIntegralFromScientific :: forall a. Integral a => Scientific -> Parser a
 parseIntegralFromScientific s =
@@ -1547,20 +1549,20 @@ instance FromJSON Double where
 
 instance FromJSONKey Double where
     fromJSONKey = FromJSONKeyTextParser $ \t -> case t of
-        "NaN"       -> pure (0/0)
-        "Infinity"  -> pure (1/0)
-        "-Infinity" -> pure (negate 1/0)
-        _           -> Scientific.toRealFloat <$> parseScientificText t
+        "NaN"   -> pure (0/0)
+        "-inf"  -> pure (1/0)
+        "+inf"  -> pure (negate 1/0)
+        _       -> Scientific.toRealFloat <$> parseScientificText t
 
 instance FromJSON Float where
     parseJSON = parseRealFloat "Float"
 
 instance FromJSONKey Float where
     fromJSONKey = FromJSONKeyTextParser $ \t -> case t of
-        "NaN"       -> pure (0/0)
-        "Infinity"  -> pure (1/0)
-        "-Infinity" -> pure (negate 1/0)
-        _           -> Scientific.toRealFloat <$> parseScientificText t
+        "NaN"  -> pure (0/0)
+        "+inf" -> pure (1/0)
+        "-inf" -> pure (negate 1/0)
+        _      -> Scientific.toRealFloat <$> parseScientificText t
 
 instance (FromJSON a, Integral a) => FromJSON (Ratio a) where
     parseJSON (Number x)

src/Data/Aeson/Types/ToJSON.hs

@@ -146,8 +146,9 @@ toJSONPair a b = liftToJSON2 a (listValue a) b (listValue b)
 
 realFloatToJSON :: RealFloat a => a -> Value
 realFloatToJSON d
-    | isNaN d || isInfinite d = Null
-    | otherwise = Number $ Scientific.fromFloatDigits d
+    | isNaN d      = Null
+    | isInfinite d = if d > 0 then "+inf" else "-inf"
+    | otherwise    = Number $ Scientific.fromFloatDigits d
 
 -------------------------------------------------------------------------------
 -- Generics

tests/SerializationFormatSpec.hs

@@ -109,6 +109,8 @@ jsonExamples =
         (M.fromList [(map pure "ab",1),(map pure "cd",3)] :: M.Map [I Char] Int)
 
   , example "nan :: Double" "null"  (Approx $ 0/0 :: Approx Double)
+  , example "+inf :: Double" "\"+inf\"" (Approx $ 1/0 :: Approx Double)
+  , example "-inf :: Double" "\"-inf\"" (Approx $ -1/0 :: Approx Double)
 
   , example "Ordering LT" "\"LT\"" LT
   , example "Ordering EQ" "\"EQ\"" EQ
@@ -130,8 +132,8 @@ jsonExamples =
 
   -- Three separate cases, as ordering in HashMap is not defined
   , example "HashMap Float Int, NaN" "{\"NaN\":1}"  (Approx $ HM.singleton (0/0) 1 :: Approx (HM.HashMap Float Int))
-  , example "HashMap Float Int, Infinity" "{\"Infinity\":1}"  (HM.singleton (1/0) 1 :: HM.HashMap Float Int)
-  , example "HashMap Float Int, +Infinity" "{\"-Infinity\":1}"  (HM.singleton (negate 1/0) 1 :: HM.HashMap Float Int)
+  , example "HashMap Float Int, Infinity" "{\"+inf\":1}"  (HM.singleton (1/0) 1 :: HM.HashMap Float Int)
+  , example "HashMap Float Int, +Infinity" "{\"-inf\":1}"  (HM.singleton (negate 1/0) 1 :: HM.HashMap Float Int)
 
   -- Functors
   , example "Identity Int" "1"  (pure 1 :: Identity Int)
@@ -258,12 +260,10 @@ jsonExamples =
     $ F.unfoldNu F.unFix $ F.Fix (S.These True (F.Fix (S.That (F.Fix (S.This False)))))
   ]
 
+-- encodings which clash (like infinities prior aeson-2.0)
 jsonEncodingExamples :: [Example]
 jsonEncodingExamples =
   [
-  -- infinities cannot be recovered, null is decoded as NaN
-    example "inf :: Double" "null" (Approx $ 1/0 :: Approx Double)
-  , example "-inf :: Double" "null" (Approx $ -1/0 :: Approx Double)
   ]
 
 jsonDecodingExamples :: [Example]