aeson-yak (empty) → 0.1.0.0

raw patch · 4 files changed

+141/−0 lines, 4 filesdep +aesondep +basesetup-changed

Dependencies added: aeson, base

Files

• LICENSE +20/−0
• Setup.hs +2/−0
• aeson-yak.cabal +40/−0
• src/Data/Aeson/Yak.hs +79/−0

@@ -0,0 +1,20 @@+Copyright (c) 2015 Theodore Lief Gannon
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be included
+in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

@@ -0,0 +1,2 @@+import Distribution.Simple
+main = defaultMain

@@ -0,0 +1,40 @@+-- Initial aeson-yak.cabal generated by cabal init.  For further 
+-- documentation, see http://haskell.org/cabal/users-guide/
+
+name:                aeson-yak
+version:             0.1.0.0
+synopsis:            Handle JSON that may or may not be a list, or exist
+description:
+  According to the standard promoted by Schema.org, the following are all
+  legally the same object:
+
+  \{ field: [data1, data2] }
+  \{ field: data }
+  \{ }
+
+  This library provides an intermediary data type and supporting functions to
+  help aeson parse and output JSON conforming to this frustrating standard.
+
+homepage:            https://github.com/tejon/aeson-yak
+license:             MIT
+license-file:        LICENSE
+author:              Theodore Lief Gannon
+maintainer:          tanuki@gmail.com
+copyright:           Copyright (c) Theodore Lief Gannon, 2015
+category:            Data
+build-type:          Simple
+-- extra-source-files:  
+cabal-version:       >=1.10
+
+source-repository head
+  type: git
+  location: https://github.com/tejon/aeson-yak
+
+library
+  exposed-modules:     Data.Aeson.Yak
+  -- other-modules:       
+  -- other-extensions:    
+  build-depends:       base >=4.8 && <4.9
+                     , aeson >= 0.4 && < 0.11
+  hs-source-dirs:      src
+  default-language:    Haskell2010

@@ -0,0 +1,79 @@+-- |
+-- There are two ways to use this library: the way with extra boilerplate,
+-- or the way with a leaky abstraction. A truly good solution would fix it
+-- all with Template Haskell; but the author is not a truly good Haskeller,
+-- so this will have to do for now.
+-- 
+-- The boilerplate way:
+-- 
+-- @
+-- data Hideous = Hideous { yak :: [String] }
+-- instance ToJSON Hideous where
+--   toJSON x = object [ "yak" .= hairy (yak x) ]
+-- instance FromJSON Hideous where
+--   parseJSON (Object o) = Hideous \<$> (shave \<$> o .:? "yak")
+-- @
+-- >>> encode $ Hideous ["foo","bar"]
+-- "{\"yak\":[\"foo\",\"bar\"]}"
+-- >>> encode $ Hideous ["baz"]
+-- "{\"yak\":\"baz\"}"
+-- >>> encode $ Hideous []
+-- "{\"yak\":null}"
+-- >>> yak <$> decode "{\"yak\":[\"foo\",\"bar\"]}"
+-- Just ["foo", "bar"]
+-- >>> yak <$> decode "{\"yak\":\"baz\"}"
+-- Just ["baz"]
+-- >>> yak <$> decode "{}"
+-- Just []
+-- 
+-- The leaky way:
+-- 
+-- @
+-- data Abhorrent = Abhorrent { yak :: Yak String }
+-- $(deriveJSON defaultOptions{omitNothingFields=True} ''Abhorrent)
+-- @
+-- >>> encode . Abhorrent . hairy $ ["shaven","shorn","sheared"]
+-- "{\"yak\":[\"shaven\",\"shorn\",\"sheared\"]}"
+-- >>> shave . yak <$> decode "{}"
+-- Just []
+-- 
+-- Which to prefer depends on how many yaks you need to deal with /vs./ how
+-- much you hate cleaning up yak droppings in the rest of your codebase.
+module Data.Aeson.Yak
+( Yak
+, hairy
+, shave)
+where
+
+import           Data.Aeson
+import           Data.Foldable
+
+-- | Data whose JSON representation may legally be an array, a single element,
+--   or null\/absent. No, please, calm down. It'll be okay. Mostly.
+--   
+--   /('Lousy' is not exposed to avoid namespace infestation./
+--   /This is open for discussion if a use case can be shown.)/
+type Yak a = Maybe (Lousy a)
+
+-- | Convert a @'Foldable'@ to a 'Yak'. Should probably be specific to lists,
+--   but what's life without a little adventure?
+hairy :: (Foldable f) => f a -> Yak a
+hairy beast = case toList beast of
+  []  -> Nothing
+  yak -> Just (Lousy yak)
+
+-- | Convert a 'Yak' to a list. Relax, and allow yourself to breathe.
+shave :: Yak a -> [a]
+shave Nothing = []
+shave (Just nit) = pick nit
+
+newtype Lousy a = Lousy { pick :: [a] }
+
+instance (ToJSON a) => ToJSON (Lousy a) where
+  toJSON nit = case pick nit of
+    [x] -> toJSON x
+    xs  -> toJSON xs
+
+instance (FromJSON a) => FromJSON (Lousy a) where
+  parseJSON vs@(Array _) = Lousy <$> parseJSON vs
+  parseJSON v = (\a -> Lousy [a]) <$> parseJSON v