Merge pull request #20 from obsidiansystems/cg-th-abstraction

 Improve/rewrite instance generation using th-abstraction and the reifyInstancesWithRigids/skolemize trick

ChangeLog.md

@@ -1,5 +1,10 @@
 # Revision history for aeson-gadt-th
 
+## 0.2.2
+
+* Do a better job determining which variables are rigid when looking for instances
+* Unify discovered instance head with argument type and make the same substitution in the context that constrains the instance we're writing
+
 ## 0.2.1.2
 
 * Add version bounds to cabal file

README.md

@@ -14,20 +14,21 @@ Example Usage:
 > {-# LANGUAGE FlexibleInstances #-}
 > {-# LANGUAGE UndecidableInstances #-}
 > {-# LANGUAGE MultiParamTypeClasses #-}
-> 
+> {-# OPTIONS_GHC -ddump-splices #-}
+>
 > import Data.Aeson
 > import Data.Aeson.GADT.TH
-> 
+>
 > import Data.Dependent.Map (DMap, Some(..))
 > import Data.Dependent.Sum (DSum)
 > import Data.Functor.Identity
 > import Data.GADT.Compare
 > import Data.GADT.Show.TH
-> 
+>
 > data A :: * -> * where
 > A_a :: A a
 > A_b :: Int -> A ()
-> 
+>
 > deriveJSONGADT ''A
 > deriveGShow ''A
 >
@@ -36,40 +37,52 @@ Example Usage:
 > B_x :: B c a
 >
 > deriveJSONGADT ''B
-> 
+>
 > data C t :: * -> * where
 > C_t :: t -> C t t
-> 
+>
 > deriveJSONGADT ''C
-> 
+>
+> data D t x :: * -> * where
+> D_t :: t -> D t x t
+> D_x :: x -> D t x x
+> D_i :: Int -> D t x Int
+>
+> deriveJSONGADT ''D
+>
+> data Auth token a where
+> Auth_Login :: String -> String -> Auth token (Either String token)
+>
+> deriveJSONGADT ''Auth
+>
 > -- Some real-world-ish examples.
-> 
+>
 > -- | Edit operations for `LabelledGraph`
 > data LabelledGraphEdit v vm em :: * -> * where
 > LabelledGraphEdit_ClearAll :: LabelledGraphEdit v vm em ()
 > LabelledGraphEdit_AddVertex :: vm -> LabelledGraphEdit v vm em v
 > LabelledGraphEdit_AddEdge :: v -> v -> em -> LabelledGraphEdit v vm em ()
 > LabelledGraphEdit_SetVertexProperties :: v -> vm -> LabelledGraphEdit v vm em ()
 > LabelledGraphEdit_SetEdgeProperties :: v -> v -> em -> LabelledGraphEdit v vm em ()
-> 
+>
 > -- | PropertyGraphEdit operatios for `PropertyGraph`
 > data PropertyGraphEdit v vp ep r where
 > PropertyGraphEdit_ClearAll :: PropertyGraphEdit v vp ep ()
 > PropertyGraphEdit_AddVertex :: (DMap vp Identity) -> PropertyGraphEdit v vp ep v
 > PropertyGraphEdit_AddEdge :: v -> v -> (DMap ep Identity) -> PropertyGraphEdit v vp ep ()
 > PropertyGraphEdit_SetVertexProperty :: GCompare vp => v -> DSum vp Identity -> PropertyGraphEdit v vp ep ()
 > PropertyGraphEdit_SetEdgeProperty :: GCompare ep => v -> v -> DSum ep Identity -> PropertyGraphEdit v vp ep ()
-> 
+>
 > -- | View operations for `LabelledGraph`
 > data LabelledGraphView v vm em :: * -> * where
 > LabelledGraphView_All :: LabelledGraphView v vm em ()
 > LabelledGraphView_GetVertexProperties :: v -> LabelledGraphView v vm em vm
 > LabelledGraphView_GetEdgeProperties :: v -> v -> LabelledGraphView v vm em em
-> 
+>
 > deriveJSONGADT ''LabelledGraphEdit
 > deriveJSONGADT ''PropertyGraphEdit
 > deriveJSONGADT ''LabelledGraphView
-> 
+>
 > main :: IO ()
 > main = do
 > putStrLn $ unlines
@@ -91,7 +104,7 @@ Example Usage:
 > , show $ encode (B_a 'a' (A_b 1))
 > , "Decoding of encoded (B_a 'a' (A_b 1)):"
 > , case (decode $ encode (B_a 'a' (A_b 1)) :: Maybe (Some (B Char))) of
-> Just (This (B_a 'a' (A_b 1))) -> "Succeeded"
+> Just (Some (B_a 'a' (A_b 1))) -> "Succeeded"
 > _-> "Failed"
 > ]
 ```

aeson-gadt-th.cabal

@@ -1,6 +1,6 @@
 cabal-version: 2.0
 name: aeson-gadt-th
-version: 0.2.1.2
+version: 0.2.2
 synopsis: Derivation of Aeson instances for GADTs
 category: JSON
 description: Template Haskell for generating ToJSON and FromJSON instances for GADTs. See <https://github.com/obsidiansystems/aeson-gadt-th/blob/master/README.md README.md> for examples.
@@ -23,9 +23,11 @@ library
  build-depends: base >= 4.8 && < 4.13
  , aeson >= 1.4 && < 1.5
  , containers >= 0.5 && < 0.7
- , dependent-sum >= 0.6.2 && < 0.7
+ , dependent-sum >= 0.6.1 && < 0.7
  , transformers >= 0.5 && < 0.6
  , template-haskell >= 2.11.0 && < 2.15
+ , th-abstraction >= 0.3.1.0 && < 0.4
+ , th-extras >= 0.0.0.4 && < 0.1
  hs-source-dirs: src
  default-language: Haskell2010