{-| Module : Z.Data.JSON Description : Fast JSON serialization/deserialization Copyright : (c) Dong Han, 2019 License : BSD Maintainer : winterland1989@gmail.com Stability : experimental Portability : non-portable Types and functions for working efficiently with JSON data, the design is quite similar to @aeson@ or @json@: * Encode to bytes can be done directly via 'EncodeJSON'. * Decode are split in two step, first we parse JSON doc into 'Value', then convert to haskell data via 'FromValue'. * 'ToValue' are provided so that other doc formats can be easily supported, such as 'YAML'. = How to use this module. This module is intended to be used qualified, e.g. @ import qualified Z.Data.JSON as JSON import Z.Data.JSON ((.:), ToValue(..), FromValue(..), EncodeJSON(..)) @ The easiest way to use the library is to define target data type, deriving 'GHC.Generics.Generic' and following instances: * 'FromValue', which provides 'fromValue' to convert 'Value' to Haskell values. * 'ToValue', which provides 'ToValue' to convert Haskell values to 'Value'. * 'EncodeJSON', which provides 'encodeJSON' to directly write Haskell value into JSON bytes. The 'Generic' instances convert(encode) Haskell data with following rules: * Constructors without payloads are encoded as JSON String, @data T = A | B@ are encoded as @\"A\"@ or @\"B\"@. * Single constructor are ingored if there're payloads, @data T = T ...@, @T@ is ingored: * Records are encoded as JSON object. @data T = T{k1 :: .., k2 :: ..}@ are encoded as @{\"k1\":...,\"k2\":...}@. * Plain product are encoded as JSON array. @data T = T t1 t2@ are encoded as "[x1,x2]". * Single field plain product are encoded as it is, i.e. @data T = T t@ are encoded as \"x\" just like its payload. * Multiple constructors are convert to single key JSON object if there're payloads: * Records are encoded as JSON object like above. @data T = A | B {k1 :: .., k2 :: ..}@ are encoded as @{\"B\":{\"k1\":...,\"k2\":...}}@ in @B .. ..@ case, or @\"A\"@ in @A@ case. * Plain product are similar to above, wrappered by an outer single-key object layer marking which constructor. These rules apply to user defined ADTs, but some built-in instances have different behaviour, namely: * @Maybe a@ are encoded as JSON @null@ in 'Nothing' case, or directly encoded to its payload in 'Just' case. * @[a]@ are encoded to JSON array, including @[Char]@, i.e. there's no special treatment to 'String'. To get JSON string, use 'T.Text' or 'Z.Data.TextBuilder.Str'. * 'NonEmpty', 'Vector', 'PrimVector', 'HashSet', 'FlatSet', 'FlatIntSet' are also encoded to JSON array. * 'HashMap', 'FlatMap', 'FlatIntMap' are encoded to JSON object. There're some modifying options if you providing a custom 'Settings', which allow you to modify field name or constructor name, but please don't produce control characters during your modification, since we assume field labels and constructor name won't contain them, thus we can save an extra escaping pass. To use constom 'Settings' just write: @ data T = T {fooBar :: Int, fooQux :: [Int]} deriving (Generic) instance ToValue T where toValue = JSON.gToValue JSON.defaultSettings{ JSON.fieldFmt = JSON.snakeCase } . from > JSON.toValue (T 0 [1,2,3]) Object [(\"foo_bar\",Number 0.0),(\"bar_qux\",Array [Number 1.0,Number 2.0,Number 3.0])] @ = Write instances manually. You can write 'ToValue' and 'FromValue' instances by hand if the 'Generic' based one doesn't suit you. Here is an example similar to aeson's. @ import qualified Z.Data.Text as T import qualified Z.Data.Vector as V import qualified Z.Data.Builder as B data Person = Person { name :: T.Text , age :: Int } deriving Show instance FromValue Person where fromValue = JSON.withFlatMapR \"Person\" $ \\ v -> Person \<$\> v .: \"name\" \<*\> v .: \"age\" instance ToValue Person where toValue (Person n a) = JSON.Object $ V.pack [(\"name\", toValue n),(\"age\", toValue a)] instance EncodeJSON Person where encodeJSON (Person n a) = B.curly $ do B.quotes \"name\" >> B.colon >> encodeJSON n B.comma B.quotes \"age\" >> B.colon >> encodeJSON a > toValue (Person \"Joe\" 12) Object [(\"name\",String \"Joe\"),(\"age\",Number 12.0)] > JSON.convert' @Person . JSON.Object $ V.pack [(\"name\",JSON.String \"Joe\"),(\"age\",JSON.Number 12.0)] Right (Person {name = \"Joe\", age = 12}) > JSON.encodeText (Person \"Joe\" 12) "{\"name\":\"Joe\",\"age\":12}" @ The 'Value' type is different from aeson's one in that we use @Vector (Text, Value)@ to represent JSON objects, thus we can choose different strategies on key duplication, the lookup map type, etc. so instead of a single 'withObject', we provide 'withHashMap', 'withHashMapR', 'withHashMap' and 'withHashMapR' which use different lookup map type, and different key order piority. Most of time 'FlatMap' is faster than 'HashMap' since we only use the lookup map once, the cost of constructing a 'HashMap' is higher. If you want to directly working on key-values, 'withKeyValues' provide key-values vector access. There're some useful tools to help write encoding code in "Z.Data.JSON.Builder" module, such as JSON string escaping tool, etc. If you don't particularly care for fast encoding, you can also use 'toValue' together with value builder, the overhead is usually very small. -} module Z.Data.JSON ( -- * Encode & Decode DecodeError , decode, decode', decodeChunks, decodeChunks', encodeBytes, encodeText, encodeTextBuilder -- * Value type , Value(..) -- * parse into JSON Value , parseValue, parseValue', parseValueChunks, parseValueChunks' -- * Convert 'Value' to Haskell data , convert, convert', Converter(..), fail', (), prependContext , PathElement(..), ConvertError , typeMismatch, fromNull, withBool, withScientific, withBoundedScientific, withRealFloat , withBoundedIntegral, withText, withArray, withKeyValues, withFlatMap, withFlatMapR , withHashMap, withHashMapR, withEmbeddedJSON , (.:), (.:?), (.:!), convertField, convertFieldMaybe, convertFieldMaybe' -- * FromValue, ToValue & EncodeJSON , ToValue(..) , FromValue(..) , EncodeJSON(..) , defaultSettings, Settings(..), snakeCase, trainCase , gToValue, gFromValue, gEncodeJSON ) where import Z.Data.JSON.Base import qualified Z.Data.Text as T import Data.Char -- | Snake casing a pascal cased constructor name or camel cased field name, words are always lower cased and separated by an -- underscore. snakeCase :: String -> T.Text {-# INLINE snakeCase #-} snakeCase = symbCase '_' -- | Train casing a pascal cased constructor name or camel cased field name, words are always lower cased and separated by -- a hyphen. trainCase :: String -> T.Text {-# INLINE trainCase #-} trainCase = symbCase '-' -------------------------------------------------------------------------------- symbCase :: Char -> String -> T.Text {-# INLINE symbCase #-} symbCase sym = T.pack . go . applyFirst toLower where go [] = [] go (x:xs) | isUpper x = sym : toLower x : go xs | otherwise = x : go xs applyFirst _ [] = [] applyFirst f (x:xs) = f x: xs