Allow to build with aeson >=2, fixes informatikr#36

Data/Aeson/Encode/Pretty.hs

@@ -1,4 +1,4 @@
-{-# LANGUAGE OverloadedStrings, RecordWildCards #-}
+{-# LANGUAGE OverloadedStrings, RecordWildCards, CPP #-}
 
 -- |Aeson-compatible pretty-printing of JSON 'Value's.
 module Data.Aeson.Encode.Pretty (
@@ -54,11 +54,15 @@ module Data.Aeson.Encode.Pretty (
     keyOrder
 ) where
 
+#if MIN_VERSION_aeson(2,0,0)
+import qualified Data.Aeson.Key as AK
+import qualified Data.Aeson.KeyMap as AKM
+#endif
 import Data.Aeson (Value(..), ToJSON(..))
 import qualified Data.Aeson.Text as Aeson
 import Data.ByteString.Lazy (ByteString)
 import Data.Function (on)
-import qualified Data.HashMap.Strict as H (toList)
+import qualified Data.HashMap.Strict as H (toList, mapKeys)
 import Data.List (intersperse, sortBy, elemIndex)
 import Data.Maybe (fromMaybe)
 import Data.Semigroup ((<>))
@@ -170,10 +174,16 @@ fromValue :: PState -> Value -> Builder
 fromValue st@PState{..} val = go val
   where
     go (Array v)  = fromCompound st ("[","]") fromValue (V.toList v)
-    go (Object m) = fromCompound st ("{","}") fromPair (pSort (H.toList m))
+    go (Object m) = fromCompound st ("{","}") fromPair (pSort (toList' m))
     go (Number x) = fromNumber st x
     go v          = Aeson.encodeToTextBuilder v
 
+#if MIN_VERSION_aeson(2,0,0)
+    toList' = fmap (\(k, v) -> (AK.toText k, v)) . AKM.toList
+#else
+    toList' = H.toList
+#endif
+
 fromCompound :: PState
              -> (Builder, Builder)
              -> (PState -> a -> Builder)

aeson-pretty.cabal

@@ -1,3 +1,4 @@
+cabal-version:  2.0
 name:           aeson-pretty
 version:        0.8.8
 license:        BSD3
@@ -7,7 +8,6 @@ copyright:      Copyright 2011 Falko Peters
 author:         Falko Peters <[email protected]>
 maintainer:     Falko Peters <[email protected]>
 stability:      experimental
-cabal-version:  >= 1.8
 homepage:       http://github.com/informatikr/aeson-pretty
 bug-reports:    http://github.com/informatikr/aeson-pretty/issues
 build-type:     Simple
@@ -40,7 +40,7 @@ library
         Data.Aeson.Encode.Pretty
 
     build-depends:
-        aeson >= 1.0,
+        aeson ^>= 1.0 || ^>=1.1 || ^>=1.2 || ^>=1.3 || ^>=1.4 || ^>=1.5 || ^>=2.0,
         base >= 4.5,
         base-compat >= 0.9,
         bytestring >= 0.9,