Support aeson 2.x

Since the 2.x series contains a number of breaking changes, don't force
people to upgrade by CPP'ing the incompatibility. May revisit after a
few releases of aeson.

opentracing/OpenTracing/Log.hs

@@ -4,6 +4,7 @@ Module: OpenTracing.Log
 Logs are structured data that occur over the lifetime of a span.
 -}
 
+{-# LANGUAGE CPP                #-}
 {-# LANGUAGE GADTs              #-}
 {-# LANGUAGE OverloadedStrings  #-}
 {-# LANGUAGE RankNTypes         #-}
@@ -31,6 +32,9 @@ import           Control.Exception
 import           Control.Lens            hiding ((.=))
 import           Data.Aeson
 import qualified Data.Aeson.Encoding     as Encoding
+#if MIN_VERSION_aeson(2, 0, 0)
+import qualified Data.Aeson.Key          as Key
+#endif
 import           Data.ByteString.Builder (Builder)
 import           Data.Foldable
 import           Data.List.NonEmpty      (NonEmpty)
@@ -84,8 +88,12 @@ type LogFieldsFormatter = forall t. Foldable t => t LogField -> Builder
 jsonAssoc :: LogFieldsFormatter
 jsonAssoc = Encoding.fromEncoding . Encoding.list go . toList
   where
-    go lf = Encoding.pairs $
-        Encoding.pair (logFieldLabel lf) (logFieldEncoding lf)
+    go lf = Encoding.pairs $ Encoding.pair (key lf) (logFieldEncoding lf)
+#if MIN_VERSION_aeson(2, 0, 0)
+    key lf = Key.fromText $ logFieldLabel lf
+#else
+    key lf = logFieldLabel lf
+#endif
 
 -- | A log formatter that encodes each `LogField` as an entry in a shared JSON object
 --

opentracing/OpenTracing/Reporting/Stdio.hs

@@ -3,6 +3,7 @@ Module: OpenTracing.Reporting.Stdio
 
 Logging reporters that emit spans to stdout, stderr and System.IO `Handles`.
 -}
+{-# LANGUAGE CPP               #-}
 {-# LANGUAGE OverloadedStrings #-}
 
 module OpenTracing.Reporting.Stdio
@@ -16,6 +17,9 @@ import Control.Lens               (view)
 import Control.Monad.IO.Class
 import Data.Aeson                 (toEncoding)
 import Data.Aeson.Encoding
+#if MIN_VERSION_aeson(2, 0, 0)
+import qualified Data.Aeson.Key as Key
+#endif
 import Data.ByteString.Lazy.Char8 (hPutStrLn)
 import Data.Foldable              (toList)
 import GHC.Stack                  (prettyCallStack)
@@ -59,10 +63,16 @@ logRecE r = pairs $
     <> pair "fields" (list logFieldE . toList $ view logFields r)
 
 logFieldE :: LogField -> Encoding
-logFieldE f = pairs . pair (logFieldLabel f) $ case f of
+logFieldE f = pairs . pair key $ case f of
     Event      x -> text x
     Message    x -> text x
     Stack      x -> string . prettyCallStack $ x
     ErrKind    x -> text x
     ErrObj     x -> string . show $ x
     LogField _ x -> string . show $ x
+  where
+#if MIN_VERSION_aeson(2, 0, 0)
+    key = Key.fromText $ logFieldLabel f
+#else
+    key = logFieldLabel f
+#endif