@@ -5,19 +5,16 @@
55{-# LANGUAGE FlexibleInstances #-}
66{-# LANGUAGE GADTs #-}
77{-# LANGUAGE MultiParamTypeClasses #-}
8−{-# LANGUAGE NamedFieldPuns #-}
8+{-# LANGUAGE NoImplicitPrelude #-}
99{-# LANGUAGE OverloadedStrings #-}
10+{-# LANGUAGE PolyKinds #-}
1011{-# LANGUAGE RecordWildCards #-}
1112{-# LANGUAGE ScopedTypeVariables #-}
1213{-# LANGUAGE TypeOperators #-}
13−{-# LANGUAGE TypeSynonymInstances #-}
14+{-# LANGUAGE TupleSections #-}
1415{-# LANGUAGE UndecidableInstances #-}
1516{-# LANGUAGE ViewPatterns #-}
1617
17−#if __GLASGOW_HASKELL__ >= 706
18−{-# LANGUAGE PolyKinds #-}
19−#endif
20−
2118#include "incoherent-compat.h"
2219#include "overlapping-compat.h"
2320
@@ -45,6 +42,9 @@ module Data.Aeson.Types.FromJSON
4542 , coerceFromJSONKeyFunction
4643 , mapFromJSONKeyFunction
4744
45+ , GFromJSONKey()
46+ , genericFromJSONKey
47+
4848 -- * List functions
4949 , listParser
5050
@@ -52,34 +52,42 @@ module Data.Aeson.Types.FromJSON
5252 , withObject
5353 , withText
5454 , withArray
55− , withNumber
5655 , withScientific
5756 , withBool
57+ , withEmbeddedJSON
5858
5959 -- * Functions
6060 , fromJSON
6161 , ifromJSON
62+ , typeMismatch
63+ , unexpected
64+ , parseField
65+ , parseFieldMaybe
66+ , parseFieldMaybe'
67+ , explicitParseField
68+ , explicitParseFieldMaybe
69+ , explicitParseFieldMaybe'
70+ , parseIndexedJSON
71+ -- ** Operators
6272 , (.:)
6373 , (.:?)
6474 , (.:!)
6575 , (.!=)
66− , typeMismatch
6776
6877 -- * Internal
6978 , parseOptionalFieldWith
7079 ) where
7180
72−import Prelude ()
7381import Prelude.Compat
7482
75−import Control.Applicative ((<|>), Const(..))
76−import Control.Monad ((<=<), zipWithM)
83+import Control.Applicative ((<|>), Const(..), liftA2)
84+import Control.Monad (zipWithM)
7785import Data.Aeson.Internal.Functions (mapKey)
86+import Data.Aeson.Parser.Internal (eitherDecodeWith, jsonEOF)
7887import Data.Aeson.Types.Generic
7988import Data.Aeson.Types.Internal
80−import Data.Attoparsec.Number (Number(..))
8189import Data.Bits (unsafeShiftR)
82−import Data.Fixed (Fixed, HasResolution)
90+import Data.Fixed (Fixed, HasResolution (resolution), Nano)
8391import Data.Functor.Compose (Compose(..))
8492import Data.Functor.Identity (Identity(..))
8593import Data.Functor.Product (Product(..))
@@ -88,26 +96,31 @@ import Data.Hashable (Hashable(..))
8896import Data.Int (Int16, Int32, Int64, Int8)
8997import Data.List.NonEmpty (NonEmpty(..))
9098import Data.Maybe (fromMaybe)
91−import Data.Monoid ((<>))
99+import Data.Semigroup ((<>))
92100import Data.Proxy (Proxy(..))
93101import Data.Ratio ((%), Ratio)
94−import Data.Scientific (Scientific)
102+import Data.Scientific (Scientific, base10Exponent)
95103import Data.Tagged (Tagged(..))
96104import Data.Text (Text, pack, unpack)
97−import Data.Time (Day, LocalTime, NominalDiffTime, TimeOfDay, UTCTime, ZonedTime)
98−import Data.Time.Format (parseTime)
99−import Data.Time.Locale.Compat (defaultTimeLocale)
105+import Data.Time (Day, DiffTime, LocalTime, NominalDiffTime, TimeOfDay, UTCTime, ZonedTime)
106+import Data.Time.Calendar.Compat (CalendarDiffDays (..), DayOfWeek (..))
107+import Data.Time.LocalTime.Compat (CalendarDiffTime (..))
108+import Data.Time.Clock.System.Compat (SystemTime (..))
109+import Data.Time.Format.Compat (parseTimeM, defaultTimeLocale)
100110import Data.Traversable as Tr (sequence)
101111import Data.Vector (Vector)
102112import Data.Version (Version, parseVersion)
113+import Data.Void (Void)
103114import Data.Word (Word16, Word32, Word64, Word8)
104115import Foreign.Storable (Storable)
116+import Foreign.C.Types (CTime (..))
105117import GHC.Generics
106118import Numeric.Natural (Natural)
107119import Text.ParserCombinators.ReadP (readP_to_S)
108120import Unsafe.Coerce (unsafeCoerce)
109121import qualified Data.Aeson.Parser.Time as Time
110122import qualified Data.Attoparsec.ByteString.Char8 as A (endOfInput, parseOnly, scientific)
123+import qualified Data.ByteString.Lazy as L
111124import qualified Data.DList as DList
112125import qualified Data.HashMap.Strict as H
113126import qualified Data.HashSet as HashSet
@@ -130,18 +143,20 @@ import qualified Data.Vector.Primitive as VP
130143import qualified Data.Vector.Storable as VS
131144import qualified Data.Vector.Unboxed as VU
132145
133−#ifndef HAS_COERCIBLE
134−#define HAS_COERCIBLE (__GLASGOW_HASKELL__ >= 707)
146+import qualified GHC.Exts as Exts
147+import qualified Data.Primitive.Array as PM
148+import qualified Data.Primitive.SmallArray as PM
149+import qualified Data.Primitive.Types as PM
150+
151+#if MIN_VERSION_primitive(0,6,4)
152+#if !MIN_VERSION_primitive(0,7,0)
153+import qualified Data.Primitive.UnliftedArray as PM
154+#endif
155+import qualified Data.Primitive.PrimArray as PM
135156#endif
136157
137−#if HAS_COERCIBLE
158+
138159import Data.Coerce (Coercible, coerce)
139−coerce' :: Coercible a b => a -> b
140−coerce' = coerce
141−#else
142−coerce' :: a -> b
143−coerce' = unsafeCoerce
144−#endif
145160
146161parseIndexedJSON :: (Value -> Parser a) -> Int -> Value -> Parser a
147162parseIndexedJSON p idx value = p value <?> Index idx
@@ -150,7 +165,7 @@ parseIndexedJSON p idx value = p value <?> Index idx
150165parseIndexedJSONPair :: (Value -> Parser a) -> (Value -> Parser b) -> Int -> Value -> Parser (a, b)
151166parseIndexedJSONPair keyParser valParser idx value = p value <?> Index idx
152167 where
153− p = withArray "(k,v)" $ \ab ->
168+ p = withArray "(k, v)" $ \ab ->
154169 let n = V.length ab
155170 in if n == 2
156171 then (,) <$> parseJSONElemAtIndex keyParser 0 ab
@@ -162,43 +177,34 @@ parseIndexedJSONPair keyParser valParser idx value = p value <?> Index idx
162177parseJSONElemAtIndex :: (Value -> Parser a) -> Int -> V.Vector Value -> Parser a
163178parseJSONElemAtIndex p idx ary = p (V.unsafeIndex ary idx) <?> Index idx
164179
165−scientificToNumber :: Scientific -> Number
166−scientificToNumber s
167− | e < 0 = D $ Scientific.toRealFloat s
168− | otherwise = I $ c * 10 ^ e
169− where
170− e = Scientific.base10Exponent s
171− c = Scientific.coefficient s
172−{-# INLINE scientificToNumber #-}
173−
174180parseRealFloat :: RealFloat a => String -> Value -> Parser a
175−parseRealFloat _ (Number s) = pure $ Scientific.toRealFloat s
176−parseRealFloat _ Null = pure (0/0)
177−parseRealFloat expected v = typeMismatch expected v
181+parseRealFloat _ (Number s) = pure $ Scientific.toRealFloat s
182+parseRealFloat _ Null = pure (0/0)
183+parseRealFloat name v = prependContext name (unexpected v)
178184{-# INLINE parseRealFloat #-}
179185
180−parseIntegralFromScientific :: forall a. Integral a => String -> Scientific -> Parser a
181−parseIntegralFromScientific expected s =
186+parseIntegralFromScientific :: forall a. Integral a => Scientific -> Parser a
187+parseIntegralFromScientific s =
182188 case Scientific.floatingOrInteger s :: Either Double a of
183189 Right x -> pure x
184− Left _ -> fail $ "Floating number specified for " ++ expected ++ ": " ++ show s
190+ Left _ -> fail $ "unexpected floating number " ++ show s
185191{-# INLINE parseIntegralFromScientific #-}
186192
187193parseIntegral :: Integral a => String -> Value -> Parser a
188−parseIntegral expected =
189− withScientific expected $ parseIntegralFromScientific expected
194+parseIntegral name =
195+ prependContext name . withBoundedScientific' parseIntegralFromScientific
190196{-# INLINE parseIntegral #-}
191197
192−parseBoundedIntegralFromScientific :: (Bounded a, Integral a) => String -> Scientific -> Parser a
193−parseBoundedIntegralFromScientific expected s = maybe
194− (fail $ expected ++ " is either floating or will cause over or underflow: " ++ show s)
198+parseBoundedIntegralFromScientific :: (Bounded a, Integral a) => Scientific -> Parser a
199+parseBoundedIntegralFromScientific s = maybe
200+ (fail $ "value is either floating or will cause over or underflow " ++ show s)
195201 pure
196202 (Scientific.toBoundedInteger s)
197203{-# INLINE parseBoundedIntegralFromScientific #-}
198204
199205parseBoundedIntegral :: (Bounded a, Integral a) => String -> Value -> Parser a
200−parseBoundedIntegral expected =
201− withScientific expected $ parseBoundedIntegralFromScientific expected
206+parseBoundedIntegral name =
207+ prependContext name . withScientific' parseBoundedIntegralFromScientific
202208{-# INLINE parseBoundedIntegral #-}
203209
204210parseScientificText :: Text -> Parser Scientific
@@ -208,13 +214,20 @@ parseScientificText
208214 . T.encodeUtf8
209215
210216parseIntegralText :: Integral a => String -> Text -> Parser a
211−parseIntegralText expected t =
212− parseScientificText t >>= parseIntegralFromScientific expected
217+parseIntegralText name t =
218+ prependContext name $
219+ parseScientificText t
220+ >>= rejectLargeExponent
221+ >>= parseIntegralFromScientific
222+ where
223+ rejectLargeExponent :: Scientific -> Parser Scientific
224+ rejectLargeExponent s = withBoundedScientific' pure (Number s)
213225{-# INLINE parseIntegralText #-}
214226
215227parseBoundedIntegralText :: (Bounded a, Integral a) => String -> Text -> Parser a
216−parseBoundedIntegralText expected t =
217− parseScientificText t >>= parseBoundedIntegralFromScientific expected
228+parseBoundedIntegralText name t =
229+ prependContext name $
230+ parseScientificText t >>= parseBoundedIntegralFromScientific
218231
219232parseOptionalFieldWith :: (Value -> Parser (Maybe a))
220233 -> Object -> Text -> Parser (Maybe a)
@@ -274,14 +287,21 @@ genericLiftParseJSON opts pj pjl = fmap to1 . gParseJSON opts (From1Args pj pjl)
274287--
275288-- The basic ways to signal a failed conversion are as follows:
276289--
277−-- * 'empty' and 'mzero' work, but are terse and uninformative
290+-- * 'fail' yields a custom error message: it is the recommended way of
291+-- reporting a failure;
292+--
293+-- * 'Control.Applicative.empty' (or 'Control.Monad.mzero') is uninformative:
294+-- use it when the error is meant to be caught by some @('<|>')@;
278295--
279−-- * 'fail' yields a custom error message
296+-- * 'typeMismatch' can be used to report a failure when the encountered value
297+-- is not of the expected JSON type; 'unexpected' is an appropriate alternative
298+-- when more than one type may be expected, or to keep the expected type
299+-- implicit.
280300--
281−-- * 'typeMismatch' produces an informative message for cases when the
282−-- value encountered is not of the expected type
301+-- 'prependFailure' (or 'modifyFailure') add more information to a parser's
302+-- error messages.
283303--
284−-- An example type and instance:
304+-- An example type and instance using 'typeMismatch' and 'prependFailure':
285305--
286306-- @
287307-- \-- Allow ourselves to write 'Text' literals.
@@ -289,15 +309,30 @@ genericLiftParseJSON opts pj pjl = fmap to1 . gParseJSON opts (From1Args pj pjl)
289309--
290310-- data Coord = Coord { x :: Double, y :: Double }
291311--
292−-- instance FromJSON Coord where
293−-- parseJSON ('Object' v) = Coord '<$>'
294−-- v '.:' \"x\" '<*>'
295−-- v '.:' \"y\"
312+-- instance 'FromJSON' Coord where
313+-- 'parseJSON' ('Object' v) = Coord
314+-- '<$>' v '.:' \"x\"
315+-- '<*>' v '.:' \"y\"
316+--
317+-- \-- We do not expect a non-'Object' value here.
318+-- \-- We could use 'Control.Applicative.empty' to fail, but 'typeMismatch'
319+-- \-- gives a much more informative error message.
320+-- 'parseJSON' invalid =
321+-- 'prependFailure' "parsing Coord failed, "
322+-- ('typeMismatch' \"Object\" invalid)
323+-- @
324+--
325+-- For this common case of only being concerned with a single
326+-- type of JSON value, the functions 'withObject', 'withScientific', etc.
327+-- are provided. Their use is to be preferred when possible, since
328+-- they are more terse. Using 'withObject', we can rewrite the above instance
329+-- (assuming the same language extension and data type) as:
296330--
297−-- \-- We do not expect a non-'Object' value here.
298−-- \-- We could use 'mzero' to fail, but 'typeMismatch'
299−-- \-- gives a much more informative error message.
300−-- parseJSON invalid = 'typeMismatch' \"Coord\" invalid
331+-- @
332+-- instance 'FromJSON' Coord where
333+-- 'parseJSON' = 'withObject' \"Coord\" $ \\v -> Coord
334+-- '<$>' v '.:' \"x\"
335+-- '<*>' v '.:' \"y\"
301336-- @
302337--
303338-- Instead of manually writing your 'FromJSON' instance, there are two options
@@ -305,7 +340,7 @@ genericLiftParseJSON opts pj pjl = fmap to1 . gParseJSON opts (From1Args pj pjl)
305340--
306341-- * "Data.Aeson.TH" provides Template Haskell functions which will derive an
307342-- instance at compile time. The generated instance is optimized for your type
308−-- so will probably be more efficient than the following two options:
343+-- so it will probably be more efficient than the following option.
309344--
310345-- * The compiler can provide a default generic implementation for
311346-- 'parseJSON'.
@@ -323,18 +358,21 @@ genericLiftParseJSON opts pj pjl = fmap to1 . gParseJSON opts (From1Args pj pjl)
323358--
324359-- data Coord = Coord { x :: Double, y :: Double } deriving 'Generic'
325360--
326−-- instance FromJSON Coord
361+-- instance 'FromJSON' Coord
327362-- @
328363--
329−-- If @DefaultSignatures@ doesn't give exactly the results you want,
330−-- you can customize the generic decoding with only a tiny amount of
331−-- effort, using 'genericParseJSON' with your preferred 'Options':
364+-- The default implementation will be equivalent to
365+-- @parseJSON = 'genericParseJSON' 'defaultOptions'@; if you need different
366+-- options, you can customize the generic decoding by defining:
332367--
333368-- @
334−-- instance FromJSON Coord where
335−-- parseJSON = 'genericParseJSON' 'defaultOptions'
369+-- customOptions = 'defaultOptions'
370+-- { 'fieldLabelModifier' = 'map' 'Data.Char.toUpper'
371+-- }
372+--
373+-- instance 'FromJSON' Coord where
374+-- 'parseJSON' = 'genericParseJSON' customOptions
336375-- @
337−
338376class FromJSON a where
339377 parseJSON :: Value -> Parser a
340378
@@ -342,13 +380,11 @@ class FromJSON a where
342380 parseJSON = genericParseJSON defaultOptions
343381
344382 parseJSONList :: Value -> Parser [a]
345− parseJSONList (Array a)
346− = zipWithM (parseIndexedJSON parseJSON) [0..]
383+ parseJSONList = withArray "[]" $ \a ->
384+ zipWithM (parseIndexedJSON parseJSON) [0..]
347385 . V.toList
348386 $ a
349387
350− parseJSONList v = typeMismatch "[a]" v
351−
352388-------------------------------------------------------------------------------
353389-- Classes and types for map keys
354390-------------------------------------------------------------------------------
@@ -360,6 +396,16 @@ class FromJSON a where
360396-- > newtype SomeId = SomeId { getSomeId :: Text }
361397-- > deriving (Eq,Ord,Hashable,FromJSONKey)
362398--
399+-- If you have a sum of nullary constructors, you may use the generic
400+-- implementation:
401+--
402+-- @
403+-- data Color = Red | Green | Blue
404+-- deriving Generic
405+--
406+-- instance 'FromJSONKey' Color where
407+-- 'fromJSONKey' = 'genericFromJSONKey' 'defaultJSONKeyOptions'
408+-- @
363409class FromJSONKey a where
364410 -- | Strategy for parsing the key of a map-like container.
365411 fromJSONKey :: FromJSONKeyFunction a
@@ -382,11 +428,7 @@ class FromJSONKey a where
382428-- At the moment this type is intentionally not exported. 'FromJSONKeyFunction'
383429-- can be inspected, but cannot be constructed.
384430data CoerceText a where
385−#if HAS_COERCIBLE
386431 CoerceText :: Coercible Text a => CoerceText a
387−#else
388− CoerceText :: CoerceText a
389−#endif
390432
391433-- | This type is related to 'ToJSONKeyFunction'. If 'FromJSONKeyValue' is used in the
392434-- 'FromJSONKey' instance, then 'ToJSONKeyValue' should be used in the 'ToJSONKey'
@@ -406,7 +448,7 @@ data FromJSONKeyFunction a
406448
407449-- | Only law abiding up to interpretation
408450instance Functor FromJSONKeyFunction where
409− fmap h (FromJSONKeyCoerce CoerceText) = FromJSONKeyText (h . coerce')
451+ fmap h (FromJSONKeyCoerce CoerceText) = FromJSONKeyText (h . coerce)
410452 fmap h (FromJSONKeyText f) = FromJSONKeyText (h . f)
411453 fmap h (FromJSONKeyTextParser f) = FromJSONKeyTextParser (fmap h . f)
412454 fmap h (FromJSONKeyValue f) = FromJSONKeyValue (fmap h . f)
@@ -420,9 +462,7 @@ instance Functor FromJSONKeyFunction where
420462--
421463-- On pre GHC 7.8 this is unconstrainted function.
422464fromJSONKeyCoerce ::
423−#if HAS_COERCIBLE
424465 Coercible Text a =>
425−#endif
426466 FromJSONKeyFunction a
427467fromJSONKeyCoerce = FromJSONKeyCoerce CoerceText
428468
@@ -430,60 +470,91 @@ fromJSONKeyCoerce = FromJSONKeyCoerce CoerceText
430470--
431471-- See note on 'fromJSONKeyCoerce'.
432472coerceFromJSONKeyFunction ::
433−#if HAS_COERCIBLE
434473 Coercible a b =>
435−#endif
436474 FromJSONKeyFunction a -> FromJSONKeyFunction b
437−#if HAS_COERCIBLE
438475coerceFromJSONKeyFunction = coerce
439−#else
440−coerceFromJSONKeyFunction (FromJSONKeyCoerce CoerceText) = FromJSONKeyCoerce CoerceText
441−coerceFromJSONKeyFunction (FromJSONKeyText f) = FromJSONKeyText (coerce' . f)
442−coerceFromJSONKeyFunction (FromJSONKeyTextParser f) = FromJSONKeyTextParser (fmap coerce' . f)
443−coerceFromJSONKeyFunction (FromJSONKeyValue f) = FromJSONKeyValue (fmap coerce' . f)
444−#endif
445476
446477{-# RULES
447478 "FromJSONKeyCoerce: fmap id" forall (x :: FromJSONKeyFunction a).
448479 fmap id x = x
449480 #-}
450−#if HAS_COERCIBLE
451481{-# RULES
452482 "FromJSONKeyCoerce: fmap coerce" forall x .
453483 fmap coerce x = coerceFromJSONKeyFunction x
454484 #-}
455−#endif
456485
457486-- | Same as 'fmap'. Provided for the consistency with 'ToJSONKeyFunction'.
458487mapFromJSONKeyFunction :: (a -> b) -> FromJSONKeyFunction a -> FromJSONKeyFunction b
459488mapFromJSONKeyFunction = fmap
460489
490+-- | 'fromJSONKey' for 'Generic' types.
491+-- These types must be sums of nullary constructors, whose names will be used
492+-- as keys for JSON objects.
493+--
494+-- See also 'genericToJSONKey'.
495+--
496+-- === __Example__
497+--
498+-- @
499+-- data Color = Red | Green | Blue
500+-- deriving 'Generic'
501+--
502+-- instance 'FromJSONKey' Color where
503+-- 'fromJSONKey' = 'genericFromJSONKey' 'defaultJSONKeyOptions'
504+-- @
505+genericFromJSONKey :: forall a. (Generic a, GFromJSONKey (Rep a))
506+ => JSONKeyOptions
507+ -> FromJSONKeyFunction a
508+genericFromJSONKey opts = FromJSONKeyTextParser $ \t ->
509+ case parseSumFromString (keyModifier opts) t of
510+ Nothing -> fail $
511+ "invalid key " ++ show t ++ ", expected one of " ++ show cnames
512+ Just k -> pure (to k)
513+ where
514+ cnames = unTagged2 (constructorTags (keyModifier opts) :: Tagged2 (Rep a) [String])
515+
516+class (ConstructorNames f, SumFromString f) => GFromJSONKey f where
517+instance (ConstructorNames f, SumFromString f) => GFromJSONKey f where
518+
461519-------------------------------------------------------------------------------
462520-- Functions needed for documentation
463521-------------------------------------------------------------------------------
464522
465523-- | Fail parsing due to a type mismatch, with a descriptive message.
466524--
467−-- Example usage:
525+-- The following wrappers should generally be prefered:
526+-- 'withObject', 'withArray', 'withText', 'withBool'.
468527--
469−-- @
470−-- instance FromJSON Coord where
471−-- parseJSON ('Object' v) = {- type matches, life is good -}
472−-- parseJSON wat = 'typeMismatch' \"Coord\" wat
473−-- @
474−typeMismatch :: String -- ^ The name of the type you are trying to parse.
528+-- ==== Error message example
529+--
530+-- > typeMismatch "Object" (String "oops")
531+-- > -- Error: "expected Object, but encountered String"
532+typeMismatch :: String -- ^ The name of the JSON type being parsed
533+ -- (@\"Object\"@, @\"Array\"@, @\"String\"@, @\"Number\"@,
534+ -- @\"Boolean\"@, or @\"Null\"@).
475535 -> Value -- ^ The actual value encountered.
476536 -> Parser a
477537typeMismatch expected actual =
478− fail $ "expected " ++ expected ++ ", encountered " ++ name
479− where
480− name = case actual of
481− Object _ -> "Object"
482− Array _ -> "Array"
483− String _ -> "String"
484− Number _ -> "Number"
485− Bool _ -> "Boolean"
486− Null -> "Null"
538+ fail $ "expected " ++ expected ++ ", but encountered " ++ typeOf actual
539+
540+-- | Fail parsing due to a type mismatch, when the expected types are implicit.
541+--
542+-- ==== Error message example
543+--
544+-- > unexpected (String "oops")
545+-- > -- Error: "unexpected String"
546+unexpected :: Value -> Parser a
547+unexpected actual = fail $ "unexpected " ++ typeOf actual
548+
549+-- | JSON type of a value, name of the head constructor.
550+typeOf :: Value -> String
551+typeOf v = case v of
552+ Object _ -> "Object"
553+ Array _ -> "Array"
554+ String _ -> "String"
555+ Number _ -> "Number"
556+ Bool _ -> "Boolean"
557+ Null -> "Null"
487558
488559-------------------------------------------------------------------------------
489560-- Lifings of FromJSON and ToJSON to unary and binary type constructors
@@ -496,7 +567,7 @@ typeMismatch expected actual =
496567--
497568-- * "Data.Aeson.TH" provides Template Haskell functions which will derive an
498569-- instance at compile time. The generated instance is optimized for your type
499−-- so will probably be more efficient than the following two options:
570+-- so it will probably be more efficient than the following option.
500571--
501572-- * The compiler can provide a default generic implementation for
502573-- 'liftParseJSON'.
@@ -514,16 +585,20 @@ typeMismatch expected actual =
514585--
515586-- data Pair a b = Pair { pairFst :: a, pairSnd :: b } deriving 'Generic1'
516587--
517−-- instance FromJSON a => FromJSON1 (Pair a)
588+-- instance 'FromJSON' a => 'FromJSON1' (Pair a)
518589-- @
519590--
520−-- If @DefaultSignatures@ doesn't give exactly the results you want,
591+-- If the default implementation doesn't give exactly the results you want,
521592-- you can customize the generic decoding with only a tiny amount of
522593-- effort, using 'genericLiftParseJSON' with your preferred 'Options':
523594--
524595-- @
525−-- instance FromJSON a => FromJSON1 (Pair a) where
526−-- liftParseJSON = 'genericLiftParseJSON' 'defaultOptions'
596+-- customOptions = 'defaultOptions'
597+-- { 'fieldLabelModifier' = 'map' 'Data.Char.toUpper'
598+-- }
599+--
600+-- instance 'FromJSON' a => 'FromJSON1' (Pair a) where
601+-- 'liftParseJSON' = 'genericLiftParseJSON' customOptions
527602-- @
528603class FromJSON1 f where
529604 liftParseJSON :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser (f a)
@@ -560,9 +635,8 @@ class FromJSON2 f where
560635 -> (Value -> Parser b)
561636 -> (Value -> Parser [b])
562637 -> Value -> Parser [f a b]
563− liftParseJSONList2 fa ga fb gb v = case v of
564− Array vals -> fmap V.toList (V.mapM (liftParseJSON2 fa ga fb gb) vals)
565− _ -> typeMismatch "[a]" v
638+ liftParseJSONList2 fa ga fb gb = withArray "[]" $ \vals ->
639+ fmap V.toList (V.mapM (liftParseJSON2 fa ga fb gb) vals)
566640
567641-- | Lift the standard 'parseJSON' function through the type constructor.
568642parseJSON2 :: (FromJSON2 f, FromJSON a, FromJSON b) => Value -> Parser (f a b)
@@ -576,7 +650,7 @@ parseJSON2 = liftParseJSON2 parseJSON parseJSONList parseJSON parseJSONList
576650-- | Helper function to use with 'liftParseJSON'. See 'Data.Aeson.ToJSON.listEncoding'.
577651listParser :: (Value -> Parser a) -> Value -> Parser [a]
578652listParser f (Array xs) = fmap V.toList (V.mapM f xs)
579−listParser _ v = typeMismatch "[a]" v
653+listParser _ v = typeMismatch "Array" v
580654{-# INLINE listParser #-}
581655
582656-------------------------------------------------------------------------------
@@ -594,48 +668,139 @@ instance (FromJSON a) => FromJSON [a] where
594668-- Functions
595669-------------------------------------------------------------------------------
596670
597−-- | @withObject expected f value@ applies @f@ to the 'Object' when @value@ is an @Object@
598−-- and fails using @'typeMismatch' expected@ otherwise.
671+-- | Add context to a failure message, indicating the name of the structure
672+-- being parsed.
673+--
674+-- > prependContext "MyType" (fail "[error message]")
675+-- > -- Error: "parsing MyType failed, [error message]"
676+prependContext :: String -> Parser a -> Parser a
677+prependContext name = prependFailure ("parsing " ++ name ++ " failed, ")
678+
679+-- | @'withObject' name f value@ applies @f@ to the 'Object' when @value@
680+-- is an 'Data.Aeson.Object' and fails otherwise.
681+--
682+-- ==== Error message example
683+--
684+-- > withObject "MyType" f (String "oops")
685+-- > -- Error: "parsing MyType failed, expected Object, but encountered String"
599686withObject :: String -> (Object -> Parser a) -> Value -> Parser a
600−withObject _ f (Object obj) = f obj
601−withObject expected _ v = typeMismatch expected v
687+withObject _ f (Object obj) = f obj
688+withObject name _ v = prependContext name (typeMismatch "Object" v)
602689{-# INLINE withObject #-}
603690
604−-- | @withText expected f value@ applies @f@ to the 'Text' when @value@ is a @String@
605−-- and fails using @'typeMismatch' expected@ otherwise.
691+-- | @'withText' name f value@ applies @f@ to the 'Text' when @value@ is a
692+-- 'Data.Aeson.String' and fails otherwise.
693+--
694+-- ==== Error message example
695+--
696+-- > withText "MyType" f Null
697+-- > -- Error: "parsing MyType failed, expected String, but encountered Null"
606698withText :: String -> (Text -> Parser a) -> Value -> Parser a
607−withText _ f (String txt) = f txt
608−withText expected _ v = typeMismatch expected v
699+withText _ f (String txt) = f txt
700+withText name _ v = prependContext name (typeMismatch "String" v)
609701{-# INLINE withText #-}
610702
611−-- | @withArray expected f value@ applies @f@ to the 'Array' when @value@ is an @Array@
612−-- and fails using @'typeMismatch' expected@ otherwise.
703+-- | @'withArray' expected f value@ applies @f@ to the 'Array' when @value@ is
704+-- an 'Data.Aeson.Array' and fails otherwise.
705+--
706+-- ==== Error message example
707+--
708+-- > withArray "MyType" f (String "oops")
709+-- > -- Error: "parsing MyType failed, expected Array, but encountered String"
613710withArray :: String -> (Array -> Parser a) -> Value -> Parser a
614−withArray _ f (Array arr) = f arr
615−withArray expected _ v = typeMismatch expected v
711+withArray _ f (Array arr) = f arr
712+withArray name _ v = prependContext name (typeMismatch "Array" v)
616713{-# INLINE withArray #-}
617714
618−-- | @withNumber expected f value@ applies @f@ to the 'Number' when @value@ is a 'Number'.
619−-- and fails using @'typeMismatch' expected@ otherwise.
620−withNumber :: String -> (Number -> Parser a) -> Value -> Parser a
621−withNumber expected f = withScientific expected (f . scientificToNumber)
622−{-# INLINE withNumber #-}
623−{-# DEPRECATED withNumber "Use withScientific instead" #-}
624−
625−-- | @withScientific expected f value@ applies @f@ to the 'Scientific' number when @value@ is a 'Number'.
626−-- and fails using @'typeMismatch' expected@ otherwise.
715+-- | @'withScientific' name f value@ applies @f@ to the 'Scientific' number
716+-- when @value@ is a 'Data.Aeson.Number' and fails using 'typeMismatch'
717+-- otherwise.
718+--
719+-- /Warning/: If you are converting from a scientific to an unbounded
720+-- type such as 'Integer' you may want to add a restriction on the
721+-- size of the exponent (see 'withBoundedScientific') to prevent
722+-- malicious input from filling up the memory of the target system.
723+--
724+-- ==== Error message example
725+--
726+-- > withScientific "MyType" f (String "oops")
727+-- > -- Error: "parsing MyType failed, expected Number, but encountered String"
627728withScientific :: String -> (Scientific -> Parser a) -> Value -> Parser a
628−withScientific _ f (Number scientific) = f scientific
629−withScientific expected _ v = typeMismatch expected v
729+withScientific _ f (Number scientific) = f scientific
730+withScientific name _ v = prependContext name (typeMismatch "Number" v)
630731{-# INLINE withScientific #-}
631732
632−-- | @withBool expected f value@ applies @f@ to the 'Bool' when @value@ is a @Bool@
633−-- and fails using @'typeMismatch' expected@ otherwise.
733+-- | A variant of 'withScientific' which doesn't use 'prependContext', so that
734+-- such context can be added separately in a way that also applies when the
735+-- continuation @f :: Scientific -> Parser a@ fails.
736+--
737+-- /Warning/: If you are converting from a scientific to an unbounded
738+-- type such as 'Integer' you may want to add a restriction on the
739+-- size of the exponent (see 'withBoundedScientific') to prevent
740+-- malicious input from filling up the memory of the target system.
741+--
742+-- ==== Error message examples
743+--
744+-- > withScientific' f (String "oops")
745+-- > -- Error: "unexpected String"
746+-- >
747+-- > prependContext "MyType" (withScientific' f (String "oops"))
748+-- > -- Error: "parsing MyType failed, unexpected String"
749+withScientific' :: (Scientific -> Parser a) -> Value -> Parser a
750+withScientific' f v = case v of
751+ Number n -> f n
752+ _ -> typeMismatch "Number" v
753+{-# INLINE withScientific' #-}
754+
755+-- | @'withBoundedScientific' name f value@ applies @f@ to the 'Scientific' number
756+-- when @value@ is a 'Number' with exponent less than or equal to 1024.
757+withBoundedScientific :: String -> (Scientific -> Parser a) -> Value -> Parser a
758+withBoundedScientific name f v = withBoundedScientific_ (prependContext name) f v
759+{-# INLINE withBoundedScientific #-}
760+
761+-- | A variant of 'withBoundedScientific' which doesn't use 'prependContext',
762+-- so that such context can be added separately in a way that also applies
763+-- when the continuation @f :: Scientific -> Parser a@ fails.
764+withBoundedScientific' :: (Scientific -> Parser a) -> Value -> Parser a
765+withBoundedScientific' f v = withBoundedScientific_ id f v
766+{-# INLINE withBoundedScientific' #-}
767+
768+-- | A variant of 'withBoundedScientific_' parameterized by a function to apply
769+-- to the 'Parser' in case of failure.
770+withBoundedScientific_ :: (Parser a -> Parser a) -> (Scientific -> Parser a) -> Value -> Parser a
771+withBoundedScientific_ whenFail f (Number scientific) =
772+ if exp10 > 1024
773+ then whenFail (fail msg)
774+ else f scientific
775+ where
776+ exp10 = base10Exponent scientific
777+ msg = "found a number with exponent " ++ show exp10 ++ ", but it must not be greater than 1024"
778+withBoundedScientific_ whenFail _ v =
779+ whenFail (typeMismatch "Number" v)
780+{-# INLINE withBoundedScientific_ #-}
781+
782+-- | @'withBool' expected f value@ applies @f@ to the 'Bool' when @value@ is a
783+-- 'Boolean' and fails otherwise.
784+--
785+-- ==== Error message example
786+--
787+-- > withBool "MyType" f (String "oops")
788+-- > -- Error: "parsing MyType failed, expected Boolean, but encountered String"
634789withBool :: String -> (Bool -> Parser a) -> Value -> Parser a
635−withBool _ f (Bool arr) = f arr
636−withBool expected _ v = typeMismatch expected v
790+withBool _ f (Bool arr) = f arr
791+withBool name _ v = prependContext name (typeMismatch "Boolean" v)
637792{-# INLINE withBool #-}
638793
794+-- | Decode a nested JSON-encoded string.
795+withEmbeddedJSON :: String -> (Value -> Parser a) -> Value -> Parser a
796+withEmbeddedJSON _ innerParser (String txt) =
797+ either fail innerParser $ eitherDecode (L.fromStrict $ T.encodeUtf8 txt)
798+ where
799+ eitherDecode = eitherFormatError . eitherDecodeWith jsonEOF ifromJSON
800+ eitherFormatError = either (Left . uncurry formatError) Right
801+withEmbeddedJSON name _ v = prependContext name (typeMismatch "String" v)
802+{-# INLINE withEmbeddedJSON #-}
803+
639804-- | Convert a value from JSON, failing if the types do not match.
640805fromJSON :: (FromJSON a) => Value -> Result a
641806fromJSON = parse parseJSON
@@ -654,9 +819,7 @@ ifromJSON = iparse parseJSON
654819-- in an object for it to be valid. If the key and value are
655820-- optional, use '.:?' instead.
656821(.:) :: (FromJSON a) => Object -> Text -> Parser a
657−obj .: key = case H.lookup key obj of
658− Nothing -> fail $ "key " ++ show key ++ " not present"
659− Just v -> parseJSON v <?> Key key
822+(.:) = explicitParseField parseJSON
660823{-# INLINE (.:) #-}
661824
662825-- | Retrieve the value associated with the given key of an 'Object'. The
@@ -667,9 +830,7 @@ obj .: key = case H.lookup key obj of
667830-- from an object without affecting its validity. If the key and
668831-- value are mandatory, use '.:' instead.
669832(.:?) :: (FromJSON a) => Object -> Text -> Parser (Maybe a)
670−obj .:? key = case H.lookup key obj of
671− Nothing -> pure Nothing
672− Just v -> parseJSON v <?> Key key
833+(.:?) = explicitParseFieldMaybe parseJSON
673834{-# INLINE (.:?) #-}
674835
675836-- | Retrieve the value associated with the given key of an 'Object'.
@@ -679,11 +840,47 @@ obj .:? key = case H.lookup key obj of
679840-- This differs from '.:?' by attempting to parse 'Null' the same as any
680841-- other JSON value, instead of interpreting it as 'Nothing'.
681842(.:!) :: (FromJSON a) => Object -> Text -> Parser (Maybe a)
682−obj .:! key = case H.lookup key obj of
683− Nothing -> pure Nothing
684− Just v -> Just <$> parseJSON v <?> Key key
843+(.:!) = explicitParseFieldMaybe' parseJSON
685844{-# INLINE (.:!) #-}
686845
846+-- | Function variant of '.:'.
847+parseField :: (FromJSON a) => Object -> Text -> Parser a
848+parseField = (.:)
849+{-# INLINE parseField #-}
850+
851+-- | Function variant of '.:?'.
852+parseFieldMaybe :: (FromJSON a) => Object -> Text -> Parser (Maybe a)
853+parseFieldMaybe = (.:?)
854+{-# INLINE parseFieldMaybe #-}
855+
856+-- | Function variant of '.:!'.
857+parseFieldMaybe' :: (FromJSON a) => Object -> Text -> Parser (Maybe a)
858+parseFieldMaybe' = (.:!)
859+{-# INLINE parseFieldMaybe' #-}
860+
861+-- | Variant of '.:' with explicit parser function.
862+--
863+-- E.g. @'explicitParseField' 'parseJSON1' :: ('FromJSON1' f, 'FromJSON' a) -> 'Object' -> 'Text' -> 'Parser' (f a)@
864+explicitParseField :: (Value -> Parser a) -> Object -> Text -> Parser a
865+explicitParseField p obj key = case H.lookup key obj of
866+ Nothing -> fail $ "key " ++ show key ++ " not found"
867+ Just v -> p v <?> Key key
868+{-# INLINE explicitParseField #-}
869+
870+-- | Variant of '.:?' with explicit parser function.
871+explicitParseFieldMaybe :: (Value -> Parser a) -> Object -> Text -> Parser (Maybe a)
872+explicitParseFieldMaybe p obj key = case H.lookup key obj of
873+ Nothing -> pure Nothing
874+ Just v -> liftParseJSON p (listParser p) v <?> Key key -- listParser isn't used by maybe instance.
875+{-# INLINE explicitParseFieldMaybe #-}
876+
877+-- | Variant of '.:!' with explicit parser function.
878+explicitParseFieldMaybe' :: (Value -> Parser a) -> Object -> Text -> Parser (Maybe a)
879+explicitParseFieldMaybe' p obj key = case H.lookup key obj of
880+ Nothing -> pure Nothing
881+ Just v -> Just <$> p v <?> Key key
882+{-# INLINE explicitParseFieldMaybe' #-}
883+
687884-- | Helper for use in combination with '.:?' to provide default
688885-- values for optional JSON object fields.
689886--
@@ -706,11 +903,47 @@ pmval .!= val = fromMaybe val <$> pmval
706903-- Generic parseJSON
707904-------------------------------------------------------------------------------
708905
906+instance GFromJSON arity V1 where
907+ -- Whereof we cannot format, thereof we cannot parse:
908+ gParseJSON _ _ _ = fail "Attempted to parse empty type"
909+
910+
709911instance OVERLAPPABLE_ (GFromJSON arity a) => GFromJSON arity (M1 i c a) where
710912 -- Meta-information, which is not handled elsewhere, is just added to the
711913 -- parsed value:
712914 gParseJSON opts fargs = fmap M1 . gParseJSON opts fargs
713915
916+-- Information for error messages
917+
918+type TypeName = String
919+type ConName = String
920+
921+-- | Add the name of the type being parsed to a parser's error messages.
922+contextType :: TypeName -> Parser a -> Parser a
923+contextType = prependContext
924+
925+-- | Add the tagKey that will be looked up while building an ADT
926+-- | Produce the error equivalent to
927+-- | Left "Error in $: parsing T failed, expected an object with keys "tag" and
928+-- | "contents", where "tag" i-- |s associated to one of ["Foo", "Bar"],
929+-- | The parser returned error was: could not find key "tag"
930+contextTag :: Text -> [String] -> Parser a -> Parser a
931+contextTag tagKey cnames = prependFailure
932+ ("expected Object with key \"" ++ unpack tagKey ++ "\"" ++
933+ " containing one of " ++ show cnames ++ ", ")
934+
935+-- | Add the name of the constructor being parsed to a parser's error messages.
936+contextCons :: ConName -> TypeName -> Parser a -> Parser a
937+contextCons cname tname = prependContext (showCons cname tname)
938+
939+-- | Render a constructor as @\"MyType(MyConstructor)\"@.
940+showCons :: ConName -> TypeName -> String
941+showCons cname tname = tname ++ "(" ++ cname ++ ")"
942+
943+--------------------------------------------------------------------------------
944+
945+-- Parsing single fields
946+
714947instance (FromJSON a) => GFromJSON arity (K1 i a) where
715948 -- Constant values are decoded using their FromJSON instance:
716949 gParseJSON _opts _ = fmap K1 . parseJSON
@@ -725,326 +958,499 @@ instance (FromJSON1 f) => GFromJSON One (Rec1 f) where
725958 -- FromJSON1 instance:
726959 gParseJSON _opts (From1Args pj pjl) = fmap Rec1 . liftParseJSON pj pjl
727960
728−instance GFromJSON arity U1 where
729− -- Empty constructors are expected to be encoded as an empty array:
730− gParseJSON _opts _ v
731− | isEmptyArray v = pure U1
732− | otherwise = typeMismatch "unit constructor (U1)" v
733−
734−instance (ConsFromJSON arity a) => GFromJSON arity (C1 c a) where
735− -- Constructors need to be decoded differently depending on whether they're
736− -- a record or not. This distinction is made by consParseJSON:
737− gParseJSON opts fargs = fmap M1 . consParseJSON opts fargs
738−
739−instance ( FromProduct arity a, FromProduct arity b
740− , ProductSize a, ProductSize b
741− ) => GFromJSON arity (a :*: b) where
742− -- Products are expected to be encoded to an array. Here we check whether we
743− -- got an array of the same size as the product, then parse each of the
744− -- product's elements using parseProduct:
745− gParseJSON opts fargs = withArray "product (:*:)" $ \arr ->
746− let lenArray = V.length arr
747− lenProduct = (unTagged2 :: Tagged2 (a :*: b) Int -> Int)
748− productSize in
749− if lenArray == lenProduct
750− then parseProduct opts fargs arr 0 lenProduct
751− else fail $ "When expecting a product of " ++ show lenProduct ++
752− " values, encountered an Array of " ++ show lenArray ++
753− " elements instead"
754−
755−instance ( AllNullary (a :+: b) allNullary
756− , ParseSum arity (a :+: b) allNullary
757− ) => GFromJSON arity (a :+: b) where
758− -- If all constructors of a sum datatype are nullary and the
759− -- 'allNullaryToStringTag' option is set they are expected to be
760− -- encoded as strings. This distinction is made by 'parseSum':
761− gParseJSON opts fargs =
762− (unTagged :: Tagged allNullary (Parser ((a :+: b) d)) ->
763− Parser ((a :+: b) d))
764− . parseSum opts fargs
765−
766961instance (FromJSON1 f, GFromJSON One g) => GFromJSON One (f :.: g) where
767962 -- If an occurrence of the last type parameter is nested inside two
768963 -- composed types, it is decoded by using the outermost type's FromJSON1
769964 -- instance to generically decode the innermost type:
770965 gParseJSON opts fargs =
771− let gpj = gParseJSON opts fargs in
772− fmap Comp1 . liftParseJSON gpj (listParser gpj)
966+ let gpj = gParseJSON opts fargs in
967+ fmap Comp1 . liftParseJSON gpj (listParser gpj)
968+
969+--------------------------------------------------------------------------------
970+
971+instance (GFromJSON' arity a, Datatype d) => GFromJSON arity (D1 d a) where
972+ -- Meta-information, which is not handled elsewhere, is just added to the
973+ -- parsed value:
974+ gParseJSON opts fargs = fmap M1 . gParseJSON' (tname :* opts :* fargs)
975+ where
976+ tname = moduleName proxy ++ "." ++ datatypeName proxy
977+ proxy = undefined :: M1 _i d _f _p
978+
979+-- | 'GFromJSON', after unwrapping the 'D1' constructor, now carrying the data
980+-- type's name.
981+class GFromJSON' arity f where
982+ gParseJSON' :: TypeName :* Options :* FromArgs arity a
983+ -> Value
984+ -> Parser (f a)
985+
986+-- | Single constructor.
987+instance ( ConsFromJSON arity a
988+ , AllNullary (C1 c a) allNullary
989+ , ParseSum arity (C1 c a) allNullary
990+ , Constructor c
991+ ) => GFromJSON' arity (C1 c a) where
992+ -- The option 'tagSingleConstructors' determines whether to wrap
993+ -- a single-constructor type.
994+ gParseJSON' p@(_ :* opts :* _)
995+ | tagSingleConstructors opts
996+ = (unTagged :: Tagged allNullary (Parser (C1 c a p)) -> Parser (C1 c a p))
997+ . parseSum p
998+ | otherwise = fmap M1 . consParseJSON (cname :* p)
999+ where
1000+ cname = conName (undefined :: M1 _i c _f _p)
1001+
1002+-- | Multiple constructors.
1003+instance ( AllNullary (a :+: b) allNullary
1004+ , ParseSum arity (a :+: b) allNullary
1005+ ) => GFromJSON' arity (a :+: b) where
1006+ -- If all constructors of a sum datatype are nullary and the
1007+ -- 'allNullaryToStringTag' option is set they are expected to be
1008+ -- encoded as strings. This distinction is made by 'parseSum':
1009+ gParseJSON' p =
1010+ (unTagged :: Tagged allNullary (Parser ((a :+: b) _d)) ->
1011+ Parser ((a :+: b) _d))
1012+ . parseSum p
7731013
7741014--------------------------------------------------------------------------------
7751015
7761016class ParseSum arity f allNullary where
777− parseSum :: Options -> FromArgs arity a
778− -> Value -> Tagged allNullary (Parser (f a))
779−
780−instance ( SumFromString (a :+: b)
781− , FromPair arity (a :+: b)
782− , FromTaggedObject arity (a :+: b)
783− , FromUntaggedValue arity (a :+: b)
784− ) => ParseSum arity (a :+: b) True where
785− parseSum opts fargs
786− | allNullaryToStringTag opts = Tagged . parseAllNullarySum opts
787− | otherwise = Tagged . parseNonAllNullarySum opts fargs
788−
789−instance ( FromPair arity (a :+: b)
790− , FromTaggedObject arity (a :+: b)
791− , FromUntaggedValue arity (a :+: b)
792− ) => ParseSum arity (a :+: b) False where
793− parseSum opts fargs = Tagged . parseNonAllNullarySum opts fargs
1017+ parseSum :: TypeName :* Options :* FromArgs arity a
1018+ -> Value
1019+ -> Tagged allNullary (Parser (f a))
1020+
1021+instance ( ConstructorNames f
1022+ , SumFromString f
1023+ , FromPair arity f
1024+ , FromTaggedObject arity f
1025+ , FromUntaggedValue arity f
1026+ ) => ParseSum arity f True where
1027+ parseSum p@(tname :* opts :* _)
1028+ | allNullaryToStringTag opts = Tagged . parseAllNullarySum tname opts
1029+ | otherwise = Tagged . parseNonAllNullarySum p
1030+
1031+instance ( ConstructorNames f
1032+ , FromPair arity f
1033+ , FromTaggedObject arity f
1034+ , FromUntaggedValue arity f
1035+ ) => ParseSum arity f False where
1036+ parseSum p = Tagged . parseNonAllNullarySum p
7941037
7951038--------------------------------------------------------------------------------
7961039
797−parseAllNullarySum :: SumFromString f => Options -> Value -> Parser (f a)
798−parseAllNullarySum opts = withText "Text" $ \key ->
799− maybe (notFound key) return $
800− parseSumFromString opts key
1040+parseAllNullarySum :: (SumFromString f, ConstructorNames f)
1041+ => TypeName -> Options -> Value -> Parser (f a)
1042+parseAllNullarySum tname opts =
1043+ withText tname $ \tag ->
1044+ maybe (badTag tag) return $
1045+ parseSumFromString modifier tag
1046+ where
1047+ badTag tag = failWithCTags tname modifier $ \cnames ->
1048+ "expected one of the tags " ++ show cnames ++
1049+ ", but found tag " ++ show tag
1050+ modifier = constructorTagModifier opts
1051+
1052+-- | Fail with an informative error message about a mismatched tag.
1053+-- The error message is parameterized by the list of expected tags,
1054+-- to be inferred from the result type of the parser.
1055+failWithCTags
1056+ :: forall f a t. ConstructorNames f
1057+ => TypeName -> (String -> t) -> ([t] -> String) -> Parser (f a)
1058+failWithCTags tname modifier f =
1059+ contextType tname . fail $ f cnames
1060+ where
1061+ cnames = unTagged2 (constructorTags modifier :: Tagged2 f [t])
8011062
8021063class SumFromString f where
803− parseSumFromString :: Options -> Text -> Maybe (f a)
1064+ parseSumFromString :: (String -> String) -> Text -> Maybe (f a)
8041065
8051066instance (SumFromString a, SumFromString b) => SumFromString (a :+: b) where
8061067 parseSumFromString opts key = (L1 <$> parseSumFromString opts key) <|>
8071068 (R1 <$> parseSumFromString opts key)
8081069
8091070instance (Constructor c) => SumFromString (C1 c U1) where
810− parseSumFromString opts key | key == name = Just $ M1 U1
811− | otherwise = Nothing
812− where
813− name = pack $ constructorTagModifier opts $
814− conName (undefined :: t c U1 p)
1071+ parseSumFromString modifier key
1072+ | key == name = Just $ M1 U1
1073+ | otherwise = Nothing
1074+ where
1075+ name = pack $ modifier $ conName (undefined :: M1 _i c _f _p)
8151076
816−--------------------------------------------------------------------------------
1077+-- For genericFromJSONKey
1078+instance SumFromString a => SumFromString (D1 d a) where
1079+ parseSumFromString modifier key = M1 <$> parseSumFromString modifier key
1080+
1081+-- | List of all constructor tags.
1082+constructorTags :: ConstructorNames a => (String -> t) -> Tagged2 a [t]
1083+constructorTags modifier =
1084+ fmap DList.toList (constructorNames' modifier)
1085+
1086+-- | List of all constructor names of an ADT, after a given conversion
1087+-- function. (Better inlining.)
1088+class ConstructorNames a where
1089+ constructorNames' :: (String -> t) -> Tagged2 a (DList.DList t)
1090+
1091+instance (ConstructorNames a, ConstructorNames b) => ConstructorNames (a :+: b) where
1092+ constructorNames' = liftA2 append constructorNames' constructorNames'
1093+ where
1094+ append
1095+ :: Tagged2 a (DList.DList t)
1096+ -> Tagged2 b (DList.DList t)
1097+ -> Tagged2 (a :+: b) (DList.DList t)
1098+ append (Tagged2 xs) (Tagged2 ys) = Tagged2 (DList.append xs ys)
1099+
1100+instance Constructor c => ConstructorNames (C1 c a) where
1101+ constructorNames' f = Tagged2 (pure (f cname))
1102+ where
1103+ cname = conName (undefined :: M1 _i c _f _p)
1104+
1105+-- For genericFromJSONKey
1106+instance ConstructorNames a => ConstructorNames (D1 d a) where
1107+ constructorNames' = retag . constructorNames'
1108+ where
1109+ retag :: Tagged2 a u -> Tagged2 (D1 d a) u
1110+ retag (Tagged2 x) = Tagged2 x
8171111
818−parseNonAllNullarySum :: ( FromPair arity (a :+: b)
819− , FromTaggedObject arity (a :+: b)
820− , FromUntaggedValue arity (a :+: b)
821− ) => Options -> FromArgs arity c
822− -> Value -> Parser ((a :+: b) c)
823−parseNonAllNullarySum opts fargs =
1112+--------------------------------------------------------------------------------
1113+parseNonAllNullarySum :: forall f c arity.
1114+ ( FromPair arity f
1115+ , FromTaggedObject arity f
1116+ , FromUntaggedValue arity f
1117+ , ConstructorNames f
1118+ ) => TypeName :* Options :* FromArgs arity c
1119+ -> Value -> Parser (f c)
1120+parseNonAllNullarySum p@(tname :* opts :* _) =
8241121 case sumEncoding opts of
8251122 TaggedObject{..} ->
826− withObject "Object" $ \obj -> do
827− tag <- obj .: pack tagFieldName
828− fromMaybe (notFound tag) $
829− parseFromTaggedObject opts fargs contentsFieldName obj tag
1123+ withObject tname $ \obj -> do
1124+ tag <- contextType tname . contextTag tagKey cnames_ $ obj .: tagKey
1125+ fromMaybe (badTag tag <?> Key tagKey) $
1126+ parseFromTaggedObject (tag :* contentsFieldName :* p) obj
1127+ where
1128+ tagKey = pack tagFieldName
1129+ badTag tag = failWith_ $ \cnames ->
1130+ "expected tag field to be one of " ++ show cnames ++
1131+ ", but found tag " ++ show tag
1132+ cnames_ = unTagged2 (constructorTags (constructorTagModifier opts) :: Tagged2 f [String])
8301133
8311134 ObjectWithSingleField ->
832− withObject "Object" $ \obj ->
833− case H.toList obj of
834− [pair@(tag, _)] -> fromMaybe (notFound tag) $
835− parsePair opts fargs pair
836− _ -> fail "Object doesn't have a single field"
1135+ withObject tname $ \obj -> case H.toList obj of
1136+ [(tag, v)] -> maybe (badTag tag) (<?> Key tag) $
1137+ parsePair (tag :* p) v
1138+ _ -> contextType tname . fail $
1139+ "expected an Object with a single pair, but found " ++
1140+ show (H.size obj) ++ " pairs"
1141+ where
1142+ badTag tag = failWith_ $ \cnames ->
1143+ "expected an Object with a single pair where the tag is one of " ++
1144+ show cnames ++ ", but found tag " ++ show tag
8371145
8381146 TwoElemArray ->
839− withArray "Array" $ \arr ->
840− if V.length arr == 2
841− then case V.unsafeIndex arr 0 of
842− String tag -> fromMaybe (notFound tag) $
843− parsePair opts fargs (tag, V.unsafeIndex arr 1)
844− _ -> fail "First element is not a String"
845− else fail "Array doesn't have 2 elements"
1147+ withArray tname $ \arr -> case V.length arr of
1148+ 2 | String tag <- V.unsafeIndex arr 0 ->
1149+ maybe (badTag tag <?> Index 0) (<?> Index 1) $
1150+ parsePair (tag :* p) (V.unsafeIndex arr 1)
1151+ | otherwise ->
1152+ contextType tname $
1153+ fail "tag element is not a String" <?> Index 0
1154+ len -> contextType tname . fail $
1155+ "expected a 2-element Array, but encountered an Array of length " ++
1156+ show len
1157+ where
1158+ badTag tag = failWith_ $ \cnames ->
1159+ "expected tag of the 2-element Array to be one of " ++
1160+ show cnames ++ ", but found tag " ++ show tag
8461161
847− UntaggedValue -> parseUntaggedValue opts fargs
1162+ UntaggedValue -> parseUntaggedValue p
1163+ where
1164+ failWith_ = failWithCTags tname (constructorTagModifier opts)
8481165
8491166--------------------------------------------------------------------------------
8501167
8511168class FromTaggedObject arity f where
852− parseFromTaggedObject :: Options -> FromArgs arity a
853− -> String -> Object
854− -> Text -> Maybe (Parser (f a))
1169+ -- The first two components of the parameter tuple are: the constructor tag
1170+ -- to match against, and the contents field name.
1171+ parseFromTaggedObject
1172+ :: Text :* String :* TypeName :* Options :* FromArgs arity a
1173+ -> Object
1174+ -> Maybe (Parser (f a))
8551175
8561176instance ( FromTaggedObject arity a, FromTaggedObject arity b) =>
8571177 FromTaggedObject arity (a :+: b) where
858− parseFromTaggedObject opts fargs contentsFieldName obj tag =
859− (fmap L1 <$> parseFromTaggedObject opts fargs contentsFieldName obj tag) <|>
860− (fmap R1 <$> parseFromTaggedObject opts fargs contentsFieldName obj tag)
1178+ parseFromTaggedObject p obj =
1179+ (fmap L1 <$> parseFromTaggedObject p obj) <|>
1180+ (fmap R1 <$> parseFromTaggedObject p obj)
8611181
862−instance ( FromTaggedObject' arity f
1182+instance ( IsRecord f isRecord
1183+ , FromTaggedObject' arity f isRecord
8631184 , Constructor c
8641185 ) => FromTaggedObject arity (C1 c f) where
865− parseFromTaggedObject opts fargs contentsFieldName obj tag
866− | tag == name = Just $ M1 <$> parseFromTaggedObject'
867− opts fargs contentsFieldName obj
868− | otherwise = Nothing
869− where
870− name = pack $ constructorTagModifier opts $
871− conName (undefined :: t c f p)
1186+ parseFromTaggedObject (tag :* contentsFieldName :* p@(_ :* opts :* _))
1187+ | tag == tag'
1188+ = Just . fmap M1 .
1189+ (unTagged :: Tagged isRecord (Parser (f a)) -> Parser (f a)) .
1190+ parseFromTaggedObject' (contentsFieldName :* cname :* p)
1191+ | otherwise = const Nothing
1192+ where
1193+ tag' = pack $ constructorTagModifier opts cname
1194+ cname = conName (undefined :: M1 _i c _f _p)
8721195
8731196--------------------------------------------------------------------------------
8741197
875−class FromTaggedObject' arity f where
876− parseFromTaggedObject' :: Options -> FromArgs arity a -> String
877− -> Object -> Parser (f a)
878−
879−class FromTaggedObject'' arity f isRecord where
880− parseFromTaggedObject'' :: Options -> FromArgs arity a -> String
881− -> Object -> Tagged isRecord (Parser (f a))
882−
883−instance ( IsRecord f isRecord
884− , FromTaggedObject'' arity f isRecord
885− ) => FromTaggedObject' arity f where
886− parseFromTaggedObject' opts fargs contentsFieldName =
887− (unTagged :: Tagged isRecord (Parser (f a)) -> Parser (f a)) .
888− parseFromTaggedObject'' opts fargs contentsFieldName
889−
890−instance (FromRecord arity f) => FromTaggedObject'' arity f True where
891− parseFromTaggedObject'' opts fargs _ =
892− Tagged . parseRecord opts fargs Nothing
893−
894−instance (GFromJSON arity f) => FromTaggedObject'' arity f False where
895− parseFromTaggedObject'' opts fargs contentsFieldName = Tagged .
896− (gParseJSON opts fargs <=< (.: pack contentsFieldName))
1198+class FromTaggedObject' arity f isRecord where
1199+ -- The first component of the parameter tuple is the contents field name.
1200+ parseFromTaggedObject'
1201+ :: String :* ConName :* TypeName :* Options :* FromArgs arity a
1202+ -> Object -> Tagged isRecord (Parser (f a))
1203+
1204+instance (RecordFromJSON arity f, FieldNames f) => FromTaggedObject' arity f True where
1205+ -- Records are unpacked in the tagged object
1206+ parseFromTaggedObject' (_ :* p) = Tagged . recordParseJSON (True :* p)
1207+
1208+instance (ConsFromJSON arity f) => FromTaggedObject' arity f False where
1209+ -- Nonnullary nonrecords are encoded in the contents field
1210+ parseFromTaggedObject' p obj = Tagged $ do
1211+ contents <- contextCons cname tname (obj .: key)
1212+ consParseJSON p' contents <?> Key key
1213+ where
1214+ key = pack contentsFieldName
1215+ contentsFieldName :* p'@(cname :* tname :* _) = p
8971216
898−instance OVERLAPPING_ FromTaggedObject'' arity U1 False where
899− parseFromTaggedObject'' _ _ _ _ = Tagged (pure U1)
1217+instance OVERLAPPING_ FromTaggedObject' arity U1 False where
1218+ -- Nullary constructors don't need a contents field
1219+ parseFromTaggedObject' _ _ = Tagged (pure U1)
9001220
9011221--------------------------------------------------------------------------------
9021222
1223+-- | Constructors need to be decoded differently depending on whether they're
1224+-- a record or not. This distinction is made by 'ConsParseJSON'.
9031225class ConsFromJSON arity f where
904− consParseJSON :: Options -> FromArgs arity a
905− -> Value -> Parser (f a)
1226+ consParseJSON
1227+ :: ConName :* TypeName :* Options :* FromArgs arity a
1228+ -> Value -> Parser (f a)
9061229
9071230class ConsFromJSON' arity f isRecord where
908− consParseJSON' :: Options -> FromArgs arity a
909− -> Maybe Text -- ^ A dummy label
910− -- (Nothing to use proper label)
911− -> Value -> Tagged isRecord (Parser (f a))
1231+ consParseJSON'
1232+ :: ConName :* TypeName :* Options :* FromArgs arity a
1233+ -> Value -> Tagged isRecord (Parser (f a))
9121234
9131235instance ( IsRecord f isRecord
9141236 , ConsFromJSON' arity f isRecord
9151237 ) => ConsFromJSON arity f where
916− consParseJSON opts fargs v = let
917− (v2,lab) = case (unwrapUnaryRecords opts,isUnary (undefined :: f a)) of
918− -- use a dummy object with a dummy label
919− (True,True) -> (object [(pack "dummy",v)], Just $ pack "dummy")
920− _ ->(v,Nothing)
921− in (unTagged :: Tagged isRecord (Parser (f a)) -> Parser (f a))
922− $ consParseJSON' opts fargs lab v2
1238+ consParseJSON p =
1239+ (unTagged :: Tagged isRecord (Parser (f a)) -> Parser (f a))
1240+ . consParseJSON' p
1241+
1242+instance OVERLAPPING_
1243+ ( GFromJSON arity a, RecordFromJSON arity (S1 s a)
1244+ ) => ConsFromJSON' arity (S1 s a) True where
1245+ consParseJSON' p@(cname :* tname :* opts :* fargs)
1246+ | unwrapUnaryRecords opts = Tagged . fmap M1 . gParseJSON opts fargs
1247+ | otherwise = Tagged . withObject (showCons cname tname) (recordParseJSON (False :* p))
1248+
1249+instance RecordFromJSON arity f => ConsFromJSON' arity f True where
1250+ consParseJSON' p@(cname :* tname :* _) =
1251+ Tagged . withObject (showCons cname tname) (recordParseJSON (False :* p))
9231252
1253+instance OVERLAPPING_
1254+ ConsFromJSON' arity U1 False where
1255+ -- Empty constructors are expected to be encoded as an empty array:
1256+ consParseJSON' (cname :* tname :* _) v =
1257+ Tagged . contextCons cname tname $ case v of
1258+ Array a | V.null a -> pure U1
1259+ | otherwise -> fail_ a
1260+ _ -> typeMismatch "Array" v
1261+ where
1262+ fail_ a = fail $
1263+ "expected an empty Array, but encountered an Array of length " ++
1264+ show (V.length a)
9241265
925−instance (FromRecord arity f) => ConsFromJSON' arity f True where
926− consParseJSON' opts fargs mlab = Tagged . withObject "record (:*:)"
927− (parseRecord opts fargs mlab)
1266+instance OVERLAPPING_
1267+ GFromJSON arity f => ConsFromJSON' arity (S1 s f) False where
1268+ consParseJSON' (_ :* _ :* opts :* fargs) =
1269+ Tagged . fmap M1 . gParseJSON opts fargs
9281270
929−instance (GFromJSON arity f) => ConsFromJSON' arity f False where
930− consParseJSON' opts fargs _ = Tagged . gParseJSON opts fargs
1271+instance (ProductFromJSON arity f, ProductSize f
1272+ ) => ConsFromJSON' arity f False where
1273+ consParseJSON' p = Tagged . productParseJSON0 p
9311274
9321275--------------------------------------------------------------------------------
9331276
934−class FromRecord arity f where
935− parseRecord :: Options -> FromArgs arity a
936− -> Maybe Text -- ^ A dummy label
937− -- (Nothing to use proper label)
938− -> Object -> Parser (f a)
1277+class FieldNames f where
1278+ fieldNames :: f a -> [Text] -> [Text]
9391279
940−instance ( FromRecord arity a
941− , FromRecord arity b
942− ) => FromRecord arity (a :*: b) where
943− parseRecord opts fargs _ obj =
944− (:*:) <$> parseRecord opts fargs Nothing obj
945− <*> parseRecord opts fargs Nothing obj
1280+instance (FieldNames a, FieldNames b) => FieldNames (a :*: b) where
1281+ fieldNames _ =
1282+ fieldNames (undefined :: a x) .
1283+ fieldNames (undefined :: b y)
9461284
947−instance OVERLAPPABLE_ (Selector s, GFromJSON arity a) =>
948− FromRecord arity (S1 s a) where
949− parseRecord opts fargs lab =
950− (<?> Key label) . gParseJSON opts fargs <=< (.: label)
1285+instance (Selector s) => FieldNames (S1 s f) where
1286+ fieldNames _ = (pack (selName (undefined :: M1 _i s _f _p)) :)
1287+
1288+class RecordFromJSON arity f where
1289+ recordParseJSON
1290+ :: Bool :* ConName :* TypeName :* Options :* FromArgs arity a
1291+ -> Object -> Parser (f a)
1292+
1293+instance ( FieldNames f
1294+ , RecordFromJSON' arity f
1295+ ) => RecordFromJSON arity f where
1296+ recordParseJSON (fromTaggedSum :* p@(cname :* tname :* opts :* _)) =
1297+ \obj -> checkUnknown obj >> recordParseJSON' p obj
9511298 where
952− label = fromMaybe defLabel lab
953− defLabel = pack . fieldLabelModifier opts $
954− selName (undefined :: t s a p)
1299+ knownFields :: H.HashMap Text ()
1300+ knownFields = H.fromList $ map (,()) $
1301+ fieldNames (undefined :: f a)
1302+ [pack (tagFieldName (sumEncoding opts)) | fromTaggedSum]
1303+ checkUnknown =
1304+ if not (rejectUnknownFields opts)
1305+ then \_ -> return ()
1306+ else \obj -> case H.keys (H.difference obj knownFields) of
1307+ [] -> return ()
1308+ unknownFields -> contextCons cname tname $
1309+ fail ("unknown fields: " ++ show unknownFields)
1310+
1311+class RecordFromJSON' arity f where
1312+ recordParseJSON'
1313+ :: ConName :* TypeName :* Options :* FromArgs arity a
1314+ -> Object -> Parser (f a)
1315+
1316+instance ( RecordFromJSON' arity a
1317+ , RecordFromJSON' arity b
1318+ ) => RecordFromJSON' arity (a :*: b) where
1319+ recordParseJSON' p obj =
1320+ (:*:) <$> recordParseJSON' p obj
1321+ <*> recordParseJSON' p obj
1322+
1323+instance OVERLAPPABLE_ (Selector s, GFromJSON arity a) =>
1324+ RecordFromJSON' arity (S1 s a) where
1325+ recordParseJSON' (cname :* tname :* opts :* fargs) obj = do
1326+ fv <- contextCons cname tname (obj .: label)
1327+ M1 <$> gParseJSON opts fargs fv <?> Key label
1328+ where
1329+ label = pack $ fieldLabelModifier opts sname
1330+ sname = selName (undefined :: M1 _i s _f _p)
9551331
9561332instance INCOHERENT_ (Selector s, FromJSON a) =>
957− FromRecord arity (S1 s (K1 i (Maybe a))) where
958− parseRecord _ _ (Just lab) obj = (M1 . K1) <$> obj .:? lab
959− parseRecord opts _ Nothing obj = (M1 . K1) <$> obj .:? pack label
960− where
961− label = fieldLabelModifier opts $
962− selName (undefined :: t s (K1 i (Maybe a)) p)
1333+ RecordFromJSON' arity (S1 s (K1 i (Maybe a))) where
1334+ recordParseJSON' (_ :* _ :* opts :* _) obj = M1 . K1 <$> obj .:? pack label
1335+ where
1336+ label = fieldLabelModifier opts sname
1337+ sname = selName (undefined :: M1 _i s _f _p)
1338+
1339+-- Parse an Option like a Maybe.
1340+instance INCOHERENT_ (Selector s, FromJSON a) =>
1341+ RecordFromJSON' arity (S1 s (K1 i (Semigroup.Option a))) where
1342+ recordParseJSON' p obj = wrap <$> recordParseJSON' p obj
1343+ where
1344+ wrap :: S1 s (K1 i (Maybe a)) p -> S1 s (K1 i (Semigroup.Option a)) p
1345+ wrap (M1 (K1 a)) = M1 (K1 (Semigroup.Option a))
9631346
9641347--------------------------------------------------------------------------------
9651348
966−class FromProduct arity f where
967− parseProduct :: Options -> FromArgs arity a
1349+productParseJSON0
1350+ :: forall f arity a. (ProductFromJSON arity f, ProductSize f)
1351+ => ConName :* TypeName :* Options :* FromArgs arity a
1352+ -> Value -> Parser (f a)
1353+ -- Products are expected to be encoded to an array. Here we check whether we
1354+ -- got an array of the same size as the product, then parse each of the
1355+ -- product's elements using productParseJSON:
1356+productParseJSON0 p@(cname :* tname :* _ :* _) =
1357+ withArray (showCons cname tname) $ \arr ->
1358+ let lenArray = V.length arr
1359+ lenProduct = (unTagged2 :: Tagged2 f Int -> Int)
1360+ productSize in
1361+ if lenArray == lenProduct
1362+ then productParseJSON p arr 0 lenProduct
1363+ else contextCons cname tname $
1364+ fail $ "expected an Array of length " ++ show lenProduct ++
1365+ ", but encountered an Array of length " ++ show lenArray
1366+
1367+--
1368+
1369+class ProductFromJSON arity f where
1370+ productParseJSON :: ConName :* TypeName :* Options :* FromArgs arity a
9681371 -> Array -> Int -> Int
9691372 -> Parser (f a)
9701373
971−instance ( FromProduct arity a
972− , FromProduct arity b
973− ) => FromProduct arity (a :*: b) where
974− parseProduct opts fargs arr ix len =
975− (:*:) <$> parseProduct opts fargs arr ix lenL
976− <*> parseProduct opts fargs arr ixR lenR
1374+instance ( ProductFromJSON arity a
1375+ , ProductFromJSON arity b
1376+ ) => ProductFromJSON arity (a :*: b) where
1377+ productParseJSON p arr ix len =
1378+ (:*:) <$> productParseJSON p arr ix lenL
1379+ <*> productParseJSON p arr ixR lenR
9771380 where
9781381 lenL = len `unsafeShiftR` 1
9791382 ixR = ix + lenL
9801383 lenR = len - lenL
9811384
982−instance (GFromJSON arity a) => FromProduct arity (S1 s a) where
983− parseProduct opts fargs arr ix _ =
984− gParseJSON opts fargs $ V.unsafeIndex arr ix
1385+instance (GFromJSON arity a) => ProductFromJSON arity (S1 s a) where
1386+ productParseJSON (_ :* _ :* opts :* fargs) arr ix _ =
1387+ M1 <$> gParseJSON opts fargs (V.unsafeIndex arr ix) <?> Index ix
9851388
9861389--------------------------------------------------------------------------------
9871390
9881391class FromPair arity f where
989− parsePair :: Options -> FromArgs arity a
990− -> Pair -> Maybe (Parser (f a))
1392+ -- The first component of the parameter tuple is the tag to match.
1393+ parsePair :: Text :* TypeName :* Options :* FromArgs arity a
1394+ -> Value
1395+ -> Maybe (Parser (f a))
9911396
9921397instance ( FromPair arity a
9931398 , FromPair arity b
9941399 ) => FromPair arity (a :+: b) where
995− parsePair opts fargs pair = (fmap L1 <$> parsePair opts fargs pair) <|>
996− (fmap R1 <$> parsePair opts fargs pair)
1400+ parsePair p pair =
1401+ (fmap L1 <$> parsePair p pair) <|>
1402+ (fmap R1 <$> parsePair p pair)
9971403
9981404instance ( Constructor c
999− , GFromJSON arity a
10001405 , ConsFromJSON arity a
10011406 ) => FromPair arity (C1 c a) where
1002− parsePair opts fargs (tag, value)
1003− | tag == tag' = Just $ gParseJSON opts fargs value
1407+ parsePair (tag :* p@(_ :* opts :* _)) v
1408+ | tag == tag' = Just $ M1 <$> consParseJSON (cname :* p) v
10041409 | otherwise = Nothing
1005− where
1006− tag' = pack $ constructorTagModifier opts $
1007− conName (undefined :: t c a p)
1410+ where
1411+ tag' = pack $ constructorTagModifier opts cname
1412+ cname = conName (undefined :: M1 _i c _a _p)
10081413
10091414--------------------------------------------------------------------------------
10101415
10111416class FromUntaggedValue arity f where
1012− parseUntaggedValue :: Options -> FromArgs arity a
1013− -> Value -> Parser (f a)
1417+ parseUntaggedValue :: TypeName :* Options :* FromArgs arity a
1418+ -> Value
1419+ -> Parser (f a)
10141420
10151421instance
10161422 ( FromUntaggedValue arity a
10171423 , FromUntaggedValue arity b
10181424 ) => FromUntaggedValue arity (a :+: b)
10191425 where
1020− parseUntaggedValue opts fargs value =
1021− L1 <$> parseUntaggedValue opts fargs value <|>
1022− R1 <$> parseUntaggedValue opts fargs value
1426+ parseUntaggedValue p value =
1427+ L1 <$> parseUntaggedValue p value <|>
1428+ R1 <$> parseUntaggedValue p value
10231429
10241430instance OVERLAPPABLE_
1025− ( GFromJSON arity a
1026− , ConsFromJSON arity a
1431+ ( ConsFromJSON arity a
1432+ , Constructor c
10271433 ) => FromUntaggedValue arity (C1 c a)
10281434 where
1029− parseUntaggedValue = gParseJSON
1435+ parseUntaggedValue p = fmap M1 . consParseJSON (cname :* p)
1436+ where
1437+ cname = conName (undefined :: M1 _i c _f _p)
10301438
10311439instance OVERLAPPING_
10321440 ( Constructor c )
10331441 => FromUntaggedValue arity (C1 c U1)
10341442 where
1035− parseUntaggedValue opts _ (String s)
1036− | s == pack (constructorTagModifier opts (conName (undefined :: t c U1 p))) =
1037− pure $ M1 U1
1038− | otherwise =
1039− fail $ "Invalid tag: " ++ unpack s
1040− parseUntaggedValue _ _ v = typeMismatch (conName (undefined :: t c U1 p)) v
1041−
1042−
1043−--------------------------------------------------------------------------------
1044−
1045−notFound :: Text -> Parser a
1046−notFound key = fail $ "The key \"" ++ unpack key ++ "\" was not found"
1047−{-# INLINE notFound #-}
1443+ parseUntaggedValue (tname :* opts :* _) v =
1444+ contextCons cname tname $ case v of
1445+ String tag
1446+ | tag == tag' -> pure $ M1 U1
1447+ | otherwise -> fail_ tag
1448+ _ -> typeMismatch "String" v
1449+ where
1450+ tag' = pack $ constructorTagModifier opts cname
1451+ cname = conName (undefined :: M1 _i c _f _p)
1452+ fail_ tag = fail $
1453+ "expected tag " ++ show tag' ++ ", but found tag " ++ show tag
10481454
10491455-------------------------------------------------------------------------------
10501456-- Instances
@@ -1102,17 +1508,20 @@ instance (FromJSON a, FromJSON b) => FromJSON (Either a b) where
11021508 parseJSON = parseJSON2
11031509 {-# INLINE parseJSON #-}
11041510
1105−
1511+instance FromJSON Void where
1512+ parseJSON _ = fail "Cannot parse Void"
1513+ {-# INLINE parseJSON #-}
11061514
11071515instance FromJSON Bool where
1108− parseJSON = withBool "Bool" pure
1516+ parseJSON (Bool b) = pure b
1517+ parseJSON v = typeMismatch "Bool" v
11091518 {-# INLINE parseJSON #-}
11101519
11111520instance FromJSONKey Bool where
11121521 fromJSONKey = FromJSONKeyTextParser $ \t -> case t of
11131522 "true" -> pure True
11141523 "false" -> pure False
1115− _ -> fail $ "Cannot parse key into Bool: " ++ T.unpack t
1524+ _ -> fail $ "cannot parse key " ++ show t ++ " into Bool"
11161525
11171526instance FromJSON Ordering where
11181527 parseJSON = withText "Ordering" $ \s ->
@@ -1120,25 +1529,30 @@ instance FromJSON Ordering where
11201529 "LT" -> return LT
11211530 "EQ" -> return EQ
11221531 "GT" -> return GT
1123− _ -> fail "Parsing Ordering value failed: expected \"LT\", \"EQ\", or \"GT\""
1532+ _ -> fail $ "parsing Ordering failed, unexpected " ++ show s ++
1533+ " (expected \"LT\", \"EQ\", or \"GT\")"
11241534
11251535instance FromJSON () where
11261536 parseJSON = withArray "()" $ \v ->
11271537 if V.null v
11281538 then pure ()
1129− else fail "Expected an empty array"
1539+ else prependContext "()" $ fail "expected an empty array"
11301540 {-# INLINE parseJSON #-}
11311541
11321542instance FromJSON Char where
1133− parseJSON = withText "Char" $ \t ->
1134− if T.compareLength t 1 == EQ
1135− then pure $ T.head t
1136− else fail "Expected a string of length 1"
1543+ parseJSON = withText "Char" parseChar
11371544 {-# INLINE parseJSON #-}
11381545
1139− parseJSONList = withText "String" $ pure . T.unpack
1546+ parseJSONList (String s) = pure (T.unpack s)
1547+ parseJSONList v = typeMismatch "String" v
11401548 {-# INLINE parseJSONList #-}
11411549
1550+parseChar :: Text -> Parser Char
1551+parseChar t =
1552+ if T.compareLength t 1 == EQ
1553+ then pure $ T.head t
1554+ else prependContext "Char" $ fail "expected a string of length 1"
1555+
11421556instance FromJSON Double where
11431557 parseJSON = parseRealFloat "Double"
11441558 {-# INLINE parseJSON #-}
@@ -1150,12 +1564,6 @@ instance FromJSONKey Double where
11501564 "-Infinity" -> pure (negate 1/0)
11511565 _ -> Scientific.toRealFloat <$> parseScientificText t
11521566
1153−instance FromJSON Number where
1154− parseJSON (Number s) = pure $ scientificToNumber s
1155− parseJSON Null = pure (D (0/0))
1156− parseJSON v = typeMismatch "Number" v
1157− {-# INLINE parseJSON #-}
1158−
11591567instance FromJSON Float where
11601568 parseJSON = parseRealFloat "Float"
11611569 {-# INLINE parseJSON #-}
@@ -1168,17 +1576,30 @@ instance FromJSONKey Float where
11681576 _ -> Scientific.toRealFloat <$> parseScientificText t
11691577
11701578instance (FromJSON a, Integral a) => FromJSON (Ratio a) where
1171− parseJSON = withObject "Rational" $ \obj ->
1172− (%) <$> obj .: "numerator"
1173− <*> obj .: "denominator"
1174− {-# INLINE parseJSON #-}
1175−
1176−-- | /WARNING:/ Only parse fixed-precision numbers from trusted input
1177−-- since an attacker could easily fill up the memory of the target
1178−-- system by specifying a scientific number with a big exponent like
1179−-- @1e1000000000@.
1579+ parseJSON (Number x)
1580+ | exp10 <= 1024
1581+ , exp10 >= -1024 = return $! realToFrac x
1582+ | otherwise = prependContext "Ratio" $ fail msg
1583+ where
1584+ exp10 = base10Exponent x
1585+ msg = "found a number with exponent " ++ show exp10
1586+ ++ ", but it must not be greater than 1024 or less than -1024"
1587+ parseJSON o = objParser o
1588+ where
1589+ objParser = withObject "Rational" $ \obj -> do
1590+ numerator <- obj .: "numerator"
1591+ denominator <- obj .: "denominator"
1592+ if denominator == 0
1593+ then fail "Ratio denominator was 0"
1594+ else pure $ numerator % denominator
1595+ {-# INLINE parseJSON #-}
1596+
1597+-- | This instance includes a bounds check to prevent maliciously
1598+-- large inputs to fill up the memory of the target system. You can
1599+-- newtype 'Scientific' and provide your own instance using
1600+-- 'withScientific' if you want to allow larger inputs.
11801601instance HasResolution a => FromJSON (Fixed a) where
1181− parseJSON = withScientific "Fixed" $ pure . realToFrac
1602+ parseJSON = prependContext "Fixed" . withBoundedScientific' (pure . realToFrac)
11821603 {-# INLINE parseJSON #-}
11831604
11841605instance FromJSON Int where
@@ -1188,10 +1609,10 @@ instance FromJSON Int where
11881609instance FromJSONKey Int where
11891610 fromJSONKey = FromJSONKeyTextParser $ parseBoundedIntegralText "Int"
11901611
1191−-- | /WARNING:/ Only parse Integers from trusted input since an
1192−-- attacker could easily fill up the memory of the target system by
1193−-- specifying a scientific number with a big exponent like
1194−-- @1e1000000000@.
1612+-- | This instance includes a bounds check to prevent maliciously
1613+-- large inputs to fill up the memory of the target system. You can
1614+-- newtype 'Scientific' and provide your own instance using
1615+-- 'withScientific' if you want to allow larger inputs.
11951616instance FromJSON Integer where
11961617 parseJSON = parseIntegral "Integer"
11971618 {-# INLINE parseJSON #-}
@@ -1200,16 +1621,21 @@ instance FromJSONKey Integer where
12001621 fromJSONKey = FromJSONKeyTextParser $ parseIntegralText "Integer"
12011622
12021623instance FromJSON Natural where
1203− parseJSON = withScientific "Natural" $ \s ->
1204− if Scientific.coefficient s < 0
1205− then fail $ "Expected a Natural number but got the negative number: " <> show s
1206− else pure $ truncate s
1624+ parseJSON value = do
1625+ integer <- parseIntegral "Natural" value
1626+ parseNatural integer
12071627
12081628instance FromJSONKey Natural where
1209− fromJSONKey = FromJSONKeyTextParser $ \t -> parseScientificText t >>= \s ->
1210− if Scientific.coefficient s < 0
1211− then fail $ "Expected a Natural number but got the negative number: " <> show s
1212− else pure $ truncate s
1629+ fromJSONKey = FromJSONKeyTextParser $ \text -> do
1630+ integer <- parseIntegralText "Natural" text
1631+ parseNatural integer
1632+
1633+parseNatural :: Integer -> Parser Natural
1634+parseNatural integer =
1635+ if integer < 0 then
1636+ fail $ "parsing Natural failed, unexpected negative number " <> show integer
1637+ else
1638+ pure $ fromIntegral integer
12131639
12141640instance FromJSON Int8 where
12151641 parseJSON = parseBoundedIntegral "Int8"
@@ -1274,6 +1700,9 @@ instance FromJSON Word64 where
12741700instance FromJSONKey Word64 where
12751701 fromJSONKey = FromJSONKeyTextParser $ parseBoundedIntegralText "Word64"
12761702
1703+instance FromJSON CTime where
1704+ parseJSON = fmap CTime . parseJSON
1705+ {-# INLINE parseJSON #-}
12771706
12781707instance FromJSON Text where
12791708 parseJSON = withText "Text" pure
@@ -1303,17 +1732,17 @@ parseVersionText = go . readP_to_S parseVersion . unpack
13031732 where
13041733 go [(v,[])] = return v
13051734 go (_ : xs) = go xs
1306− go _ = fail "could not parse Version"
1735+ go _ = fail "parsing Version failed"
13071736
13081737-------------------------------------------------------------------------------
13091738-- semigroups NonEmpty
13101739-------------------------------------------------------------------------------
13111740
13121741instance FromJSON1 NonEmpty where
1313− liftParseJSON p _ = withArray "NonEmpty a" $
1742+ liftParseJSON p _ = withArray "NonEmpty" $
13141743 (>>= ne) . Tr.sequence . zipWith (parseIndexedJSON p) [0..] . V.toList
13151744 where
1316− ne [] = fail "Expected a NonEmpty but got an empty list"
1745+ ne [] = fail "parsing NonEmpty failed, unexpected empty list"
13171746 ne (x:xs) = pure (x :| xs)
13181747 {-# INLINE liftParseJSON #-}
13191748
@@ -1334,7 +1763,7 @@ instance FromJSON Scientific where
13341763-------------------------------------------------------------------------------
13351764
13361765instance FromJSON1 DList.DList where
1337− liftParseJSON p _ = withArray "DList a" $
1766+ liftParseJSON p _ = withArray "DList" $
13381767 fmap DList.fromList .
13391768 Tr.sequence . zipWith (parseIndexedJSON p) [0..] . V.toList
13401769 {-# INLINE liftParseJSON #-}
@@ -1411,7 +1840,7 @@ instance (FromJSON1 f, FromJSON1 g) => FromJSON1 (Sum f g) where
14111840 inr = "InR"
14121841
14131842 liftParseJSON _ _ _ = fail $
1414− "expected an object with a single property " ++
1843+ "parsing Sum failed, expected an object with a single property " ++
14151844 "where the property key should be either " ++
14161845 "\"InL\" or \"InR\""
14171846 {-# INLINE liftParseJSON #-}
@@ -1425,7 +1854,7 @@ instance (FromJSON1 f, FromJSON1 g, FromJSON a) => FromJSON (Sum f g a) where
14251854-------------------------------------------------------------------------------
14261855
14271856instance FromJSON1 Seq.Seq where
1428− liftParseJSON p _ = withArray "Seq a" $
1857+ liftParseJSON p _ = withArray "Seq" $
14291858 fmap Seq.fromList .
14301859 Tr.sequence . zipWith (parseIndexedJSON p) [0..] . V.toList
14311860 {-# INLINE liftParseJSON #-}
@@ -1459,15 +1888,15 @@ instance FromJSON a => FromJSON (IntMap.IntMap a) where
14591888
14601889instance (FromJSONKey k, Ord k) => FromJSON1 (M.Map k) where
14611890 liftParseJSON p _ = case fromJSONKey of
1462− FromJSONKeyCoerce _-> withObject "Map k v" $
1891+ FromJSONKeyCoerce _ -> withObject "Map" $
14631892 fmap (H.foldrWithKey (M.insert . unsafeCoerce) M.empty) . H.traverseWithKey (\k v -> p v <?> Key k)
1464− FromJSONKeyText f -> withObject "Map k v" $
1893+ FromJSONKeyText f -> withObject "Map" $
14651894 fmap (H.foldrWithKey (M.insert . f) M.empty) . H.traverseWithKey (\k v -> p v <?> Key k)
1466− FromJSONKeyTextParser f -> withObject "Map k v" $
1895+ FromJSONKeyTextParser f -> withObject "Map" $
14671896 H.foldrWithKey (\k v m -> M.insert <$> f k <?> Key k <*> p v <?> Key k <*> m) (pure M.empty)
1468− FromJSONKeyValue f -> withArray "Map k v" $ \arr ->
1469− M.fromList <$> (Tr.sequence .
1470− zipWith (parseIndexedJSONPair f p) [0..] . V.toList $ arr)
1897+ FromJSONKeyValue f -> withArray "Map" $ \arr ->
1898+ fmap M.fromList . Tr.sequence .
1899+ zipWith (parseIndexedJSONPair f p) [0..] . V.toList $ arr
14711900 {-# INLINE liftParseJSON #-}
14721901
14731902instance (FromJSONKey k, Ord k, FromJSON v) => FromJSON (M.Map k v) where
@@ -1493,18 +1922,18 @@ instance (FromJSON v) => FromJSON (Tree.Tree v) where
14931922
14941923instance FromJSON UUID.UUID where
14951924 parseJSON = withText "UUID" $
1496− maybe (fail "Invalid UUID") pure . UUID.fromText
1925+ maybe (fail "invalid UUID") pure . UUID.fromText
14971926
14981927instance FromJSONKey UUID.UUID where
14991928 fromJSONKey = FromJSONKeyTextParser $
1500− maybe (fail "Invalid UUID") pure . UUID.fromText
1929+ maybe (fail "invalid UUID") pure . UUID.fromText
15011930
15021931-------------------------------------------------------------------------------
15031932-- vector
15041933-------------------------------------------------------------------------------
15051934
15061935instance FromJSON1 Vector where
1507− liftParseJSON p _ = withArray "Vector a" $
1936+ liftParseJSON p _ = withArray "Vector" $
15081937 V.mapM (uncurry $ parseIndexedJSON p) . V.indexed
15091938 {-# INLINE liftParseJSON #-}
15101939
@@ -1518,14 +1947,14 @@ vectorParseJSON s = withArray s $ fmap V.convert . V.mapM (uncurry $ parseIndexe
15181947{-# INLINE vectorParseJSON #-}
15191948
15201949instance (Storable a, FromJSON a) => FromJSON (VS.Vector a) where
1521− parseJSON = vectorParseJSON "Data.Vector.Storable.Vector a"
1950+ parseJSON = vectorParseJSON "Data.Vector.Storable.Vector"
15221951
15231952instance (VP.Prim a, FromJSON a) => FromJSON (VP.Vector a) where
1524− parseJSON = vectorParseJSON "Data.Vector.Primitive.Vector a"
1953+ parseJSON = vectorParseJSON "Data.Vector.Primitive.Vector"
15251954 {-# INLINE parseJSON #-}
15261955
15271956instance (VG.Vector VU.Vector a, FromJSON a) => FromJSON (VU.Vector a) where
1528− parseJSON = vectorParseJSON "Data.Vector.Unboxed.Vector a"
1957+ parseJSON = vectorParseJSON "Data.Vector.Unboxed.Vector"
15291958 {-# INLINE parseJSON #-}
15301959
15311960-------------------------------------------------------------------------------
@@ -1539,15 +1968,15 @@ instance (Eq a, Hashable a, FromJSON a) => FromJSON (HashSet.HashSet a) where
15391968
15401969instance (FromJSONKey k, Eq k, Hashable k) => FromJSON1 (H.HashMap k) where
15411970 liftParseJSON p _ = case fromJSONKey of
1542− FromJSONKeyCoerce _ -> withObject "HashMap ~Text v" $
1971+ FromJSONKeyCoerce _ -> withObject "HashMap ~Text" $
15431972 uc . H.traverseWithKey (\k v -> p v <?> Key k)
1544− FromJSONKeyText f -> withObject "HashMap k v" $
1973+ FromJSONKeyText f -> withObject "HashMap" $
15451974 fmap (mapKey f) . H.traverseWithKey (\k v -> p v <?> Key k)
1546− FromJSONKeyTextParser f -> withObject "HashMap k v" $
1975+ FromJSONKeyTextParser f -> withObject "HashMap" $
15471976 H.foldrWithKey (\k v m -> H.insert <$> f k <?> Key k <*> p v <?> Key k <*> m) (pure H.empty)
1548− FromJSONKeyValue f -> withArray "Map k v" $ \arr ->
1549− H.fromList <$> (Tr.sequence .
1550− zipWith (parseIndexedJSONPair f p) [0..] . V.toList $ arr)
1977+ FromJSONKeyValue f -> withArray "Map" $ \arr ->
1978+ fmap H.fromList . Tr.sequence .
1979+ zipWith (parseIndexedJSONPair f p) [0..] . V.toList $ arr
15511980 where
15521981 uc :: Parser (H.HashMap Text v) -> Parser (H.HashMap k v)
15531982 uc = unsafeCoerce
@@ -1568,11 +1997,33 @@ instance FromJSON DotNetTime where
15681997 parseJSON = withText "DotNetTime" $ \t ->
15691998 let (s,m) = T.splitAt (T.length t - 5) t
15701999 t' = T.concat [s,".",m]
1571− in case parseTime defaultTimeLocale "/Date(%s%Q)/" (unpack t') of
2000+ in case parseTimeM True defaultTimeLocale "/Date(%s%Q)/" (unpack t') of
15722001 Just d -> pure (DotNetTime d)
15732002 _ -> fail "could not parse .NET time"
15742003 {-# INLINE parseJSON #-}
15752004
2005+-------------------------------------------------------------------------------
2006+-- primitive
2007+-------------------------------------------------------------------------------
2008+
2009+instance FromJSON a => FromJSON (PM.Array a) where
2010+ -- note: we could do better than this if vector exposed the data
2011+ -- constructor in Data.Vector.
2012+ parseJSON = fmap Exts.fromList . parseJSON
2013+
2014+instance FromJSON a => FromJSON (PM.SmallArray a) where
2015+ parseJSON = fmap Exts.fromList . parseJSON
2016+
2017+#if MIN_VERSION_primitive(0,6,4)
2018+instance (PM.Prim a,FromJSON a) => FromJSON (PM.PrimArray a) where
2019+ parseJSON = fmap Exts.fromList . parseJSON
2020+
2021+#if !MIN_VERSION_primitive(0,7,0)
2022+instance (PM.PrimUnlifted a,FromJSON a) => FromJSON (PM.UnliftedArray a) where
2023+ parseJSON = fmap Exts.fromList . parseJSON
2024+#endif
2025+#endif
2026+
15762027-------------------------------------------------------------------------------
15772028-- time
15782029-------------------------------------------------------------------------------
@@ -1598,6 +2049,17 @@ instance FromJSONKey LocalTime where
15982049 fromJSONKey = FromJSONKeyTextParser (Time.run Time.localTime)
15992050
16002051
2052+-- | Supported string formats:
2053+--
2054+-- @YYYY-MM-DD HH:MM Z@
2055+-- @YYYY-MM-DD HH:MM:SS Z@
2056+-- @YYYY-MM-DD HH:MM:SS.SSS Z@
2057+--
2058+-- The first space may instead be a @T@, and the second space is
2059+-- optional. The @Z@ represents UTC. The @Z@ may be replaced with a
2060+-- time zone offset of the form @+0000@ or @-08:00@, where the first
2061+-- two digits are hours, the @:@ is optional and the second two digits
2062+-- (also optional) are minutes.
16012063instance FromJSON ZonedTime where
16022064 parseJSON = withText "ZonedTime" (Time.run Time.zonedTime)
16032065
@@ -1612,14 +2074,57 @@ instance FromJSONKey UTCTime where
16122074 fromJSONKey = FromJSONKeyTextParser (Time.run Time.utcTime)
16132075
16142076
1615−-- | /WARNING:/ Only parse lengths of time from trusted input
1616−-- since an attacker could easily fill up the memory of the target
1617−-- system by specifying a scientific number with a big exponent like
1618−-- @1e1000000000@.
2077+-- | This instance includes a bounds check to prevent maliciously
2078+-- large inputs to fill up the memory of the target system. You can
2079+-- newtype 'Scientific' and provide your own instance using
2080+-- 'withScientific' if you want to allow larger inputs.
16192081instance FromJSON NominalDiffTime where
1620− parseJSON = withScientific "NominalDiffTime" $ pure . realToFrac
2082+ parseJSON = withBoundedScientific "NominalDiffTime" $ pure . realToFrac
2083+ {-# INLINE parseJSON #-}
2084+
2085+
2086+-- | This instance includes a bounds check to prevent maliciously
2087+-- large inputs to fill up the memory of the target system. You can
2088+-- newtype 'Scientific' and provide your own instance using
2089+-- 'withScientific' if you want to allow larger inputs.
2090+instance FromJSON DiffTime where
2091+ parseJSON = withBoundedScientific "DiffTime" $ pure . realToFrac
16212092 {-# INLINE parseJSON #-}
16222093
2094+instance FromJSON SystemTime where
2095+ parseJSON v = prependContext "SystemTime" $ do
2096+ n <- parseJSON v
2097+ let n' = floor (n * fromInteger (resolution n) :: Nano)
2098+ let (secs, nano) = n' `divMod` resolution n
2099+ return (MkSystemTime (fromInteger secs) (fromInteger nano))
2100+
2101+instance FromJSON CalendarDiffTime where
2102+ parseJSON = withObject "CalendarDiffTime" $ \obj -> CalendarDiffTime
2103+ <$> obj .: "months"
2104+ <*> obj .: "time"
2105+
2106+instance FromJSON CalendarDiffDays where
2107+ parseJSON = withObject "CalendarDiffDays" $ \obj -> CalendarDiffDays
2108+ <$> obj .: "months"
2109+ <*> obj .: "days"
2110+
2111+instance FromJSON DayOfWeek where
2112+ parseJSON = withText "DaysOfWeek" parseDayOfWeek
2113+
2114+parseDayOfWeek :: T.Text -> Parser DayOfWeek
2115+parseDayOfWeek t = case T.toLower t of
2116+ "monday" -> return Monday
2117+ "tuesday" -> return Tuesday
2118+ "wednesday" -> return Wednesday
2119+ "thursday" -> return Thursday
2120+ "friday" -> return Friday
2121+ "saturday" -> return Saturday
2122+ "sunday" -> return Sunday
2123+ _ -> fail "Invalid week day"
2124+
2125+instance FromJSONKey DayOfWeek where
2126+ fromJSONKey = FromJSONKeyTextParser parseDayOfWeek
2127+
16232128-------------------------------------------------------------------------------
16242129-- base Monoid/Semigroup
16252130-------------------------------------------------------------------------------
@@ -1740,14 +2245,15 @@ instance FromJSON a => FromJSON (Semigroup.Option a) where
17402245
17412246instance FromJSON1 Proxy where
17422247 {-# INLINE liftParseJSON #-}
1743− liftParseJSON _ _ Null = pure Proxy
1744− liftParseJSON _ _ v = typeMismatch "Proxy" v
2248+ liftParseJSON _ _ = fromNull "Proxy" Proxy
17452249
17462250instance FromJSON (Proxy a) where
17472251 {-# INLINE parseJSON #-}
1748− parseJSON Null = pure Proxy
1749− parseJSON v = typeMismatch "Proxy" v
2252+ parseJSON = fromNull "Proxy" Proxy
17502253
2254+fromNull :: String -> a -> Value -> Parser a
2255+fromNull _ a Null = pure a
2256+fromNull c _ v = prependContext c (typeMismatch "Null" v)
17512257
17522258instance FromJSON2 Tagged where
17532259 liftParseJSON2 _ _ p _ = fmap Tagged . p
@@ -1774,10 +2280,7 @@ instance (FromJSON a, FromJSON b, FromJSON c) => FromJSONKey (a,b,c)
17742280instance (FromJSON a, FromJSON b, FromJSON c, FromJSON d) => FromJSONKey (a,b,c,d)
17752281
17762282instance FromJSONKey Char where
1777− fromJSONKey = FromJSONKeyTextParser $ \t ->
1778− if T.length t == 1
1779− then return (T.index t 0)
1780− else typeMismatch "Expected Char but String didn't contain exactly one character" (String t)
2283+ fromJSONKey = FromJSONKeyTextParser parseChar
17812284 fromJSONKeyList = FromJSONKeyText T.unpack
17822285
17832286instance (FromJSONKey a, FromJSON a) => FromJSONKey [a] where