diff --git a/Data/Aeson/AutoType/Alternative.hs b/Data/Aeson/AutoType/Alternative.hs new file mode 100644 --- /dev/null +++ b/Data/Aeson/AutoType/Alternative.hs @@ -0,0 +1,48 @@ +{-# LANGUAGE TypeOperators #-} +-- | This module defines data type (a :|: b) that behaves all like @Either@, +-- except that has no tag in JSON representation as used by @FromJSON@ and @ToJSON@. +module Data.Aeson.AutoType.Alternative( + (:|:)(..) + , toEither, fromEither + , alt + ) where + +import Data.Aeson +import Control.Applicative + +-- | Data type (a :|: b) that behaves all like @Either@, +-- except that has no tag in JSON representation as used by @FromJSON@ and @ToJSON@. +data a :|: b = AltLeft a + | AltRight b + deriving(Show,Eq,Ord) +infixr 5 :|: + +-- | Convert to @Either@ datatype. +toEither :: a :|: b -> Either a b +toEither (AltLeft a) = Left a +toEither (AltRight b) = Right b +{-# INLINE toEither #-} + +-- | Convert from @Either@ datatype. +fromEither :: Either a b -> a :|: b +fromEither (Left a) = AltLeft a +fromEither (Right b) = AltRight b +{-# INLINE fromEither #-} + +-- | Deconstruct the type with two functions corresponding to constructors. +-- This is like @either@. +alt :: (a -> c) -> (b -> c) -> a :|: b -> c +alt f _ (AltLeft a) = f a +alt _ g (AltRight b) = g b +infixr 5 `alt` + +instance (ToJSON a, ToJSON b) => ToJSON (a :|: b) where + toJSON (AltLeft a) = toJSON a + toJSON (AltRight b) = toJSON b + {-# INLINE toJSON #-} + +instance (FromJSON a, FromJSON b) => FromJSON (a :|: b) where + parseJSON input = (AltLeft <$> parseJSON input) <|> + (AltRight <$> parseJSON input) <|> + fail ("Neither alternative was found for: " ++ show input) + {-# INLINE parseJSON #-} diff --git a/LICENSE b/LICENSE new file mode 100644 --- /dev/null +++ b/LICENSE @@ -0,0 +1,34 @@ +This repository contains some test JSON examples in test/*.json +that is downloaded from Twitter API and http://www.jquery4u.com/json/. +Naturally these are covered by other licenses. + +Code copyright (c) 2014, Michal J. Gajda + +All rights reserved. + +Redistribution and use in source and binary forms, with or without +modification, are permitted provided that the following conditions are met: + + * Redistributions of source code must retain the above copyright + notice, this list of conditions and the following disclaimer. + + * Redistributions in binary form must reproduce the above + copyright notice, this list of conditions and the following + disclaimer in the documentation and/or other materials provided + with the distribution. + + * Neither the name of Michal J. Gajda nor the names of other + contributors may be used to endorse or promote products derived + from this software without specific prior written permission. + +THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS +"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT +LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR +A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT +OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, +SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT +LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, +DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY +THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT +(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE +OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. diff --git a/README.md b/README.md new file mode 100644 --- /dev/null +++ b/README.md @@ -0,0 +1,3 @@ +json-alt +======== +Runtime module for `json-autotype` that allows easy parsing of JSON values that have more than a single Haskell type. diff --git a/Setup.hs b/Setup.hs new file mode 100644 --- /dev/null +++ b/Setup.hs @@ -0,0 +1,2 @@ +import Distribution.Simple +main = defaultMain diff --git a/changelog.md b/changelog.md new file mode 100644 --- /dev/null +++ b/changelog.md @@ -0,0 +1,4 @@ +Changelog +========= + 1.0.0 Nov 2018 + * Split `json-alt` from `json-autotype` package as a runtime library. diff --git a/json-alt.cabal b/json-alt.cabal new file mode 100644 --- /dev/null +++ b/json-alt.cabal @@ -0,0 +1,77 @@ +-- Build information for the package. +name: json-alt +version: 1.0.0 +synopsis: Union 'alternative' or Either that has untagged JSON encoding. +description: Parsing JSON with Aeson often requires decoding fields + that have more than one Haskell type. + . + So we have: + ``` + data a :|: b = AltLeft a + | AltLeft b + + printIt = print . (fromJSON :: ByteString -> Int :|: Bool) + main = do + printIt "1" -- AltLeft 1 + printIt "true" -- AltRight True + printIt "null" -- errors! + ``` + To generate types for larger JSON documents, + you might use `json-autotype`. + . + This is separate package so that users + do not have to keep `json-autotype` as runtime + dependency. + . + See +homepage: https://github.com/mgajda/json-autotype +license: BSD3 +license-file: LICENSE +stability: stable +author: Michal J. Gajda +maintainer: simons@cryp.to + mjgajda@gmail.com +copyright: Copyright by Michal J. Gajda '2014-'2018 +category: Data, Tools +build-type: Simple +extra-source-files: README.md changelog.md +cabal-version: >=1.10 +bug-reports: https://github.com/mgajda/json-autotype/issues +tested-with: GHC==7.6.1 + , GHC==7.6.2 + , GHC==7.6.3 + , GHC==7.8.1 + , GHC==7.8.2 + , GHC==7.8.3 + , GHC==7.8.4 + , GHC==7.10.1 + , GHC==7.10.2 + , GHC==7.10.3 + , GHC==8.0.1 + , GHC==8.0.2 + , GHC==8.2.2 + , GHC==8.4.1 + , GHC==8.4.2 + , GHC==8.4.3 + , GHC==8.4.4 + , GHC==8.6.2 + , GHC==8.6.1 + +source-repository head + type: git + location: https://github.com/mgajda/json-autotype.git + +library + exposed-modules: Data.Aeson.AutoType.Alternative + + other-extensions: TemplateHaskell, + ScopedTypeVariables, + OverloadedStrings, + FlexibleInstances, + MultiParamTypeClasses, + DeriveDataTypeable, + DeriveGeneric, + RecordWildCards + build-depends: base >=4.3 && <5, + aeson >=1.2.1 && <1.5 + default-language: Haskell2010