Deal with JSON parse errors #511

yesod-json/Yesod/Json.hs

@@ -45,7 +45,7 @@ import Data.Text.Lazy.Builder (fromLazyText)
 import Data.Text.Lazy.Encoding (decodeUtf8)
 import Data.Text.Lazy.Builder (toLazyText)
 import qualified Blaze.ByteString.Builder.Char.Utf8 as Blaze
-import Data.Conduit (($$))
+import Data.Conduit
 import Network.Wai (requestBody, requestHeaders)
 import Network.Wai.Parse (parseHttpAccept)
 import qualified Data.ByteString.Char8 as B8
@@ -88,7 +88,13 @@ jsonToRepJson = return . RepJson . toContent . J.toJSON
 parseJsonBody :: J.FromJSON a => GHandler sub master (J.Result a)
 parseJsonBody = do
     req <- waiRequest
-    fmap J.fromJSON $ lift $ requestBody req $$ sinkParser JP.value'
+    eValue <- lift
+            $ runExceptionT
+            $ transPipe lift (requestBody req)
+           $$ sinkParser JP.value'
+    return $ case eValue of
+        Left e -> J.Error $ show e
+        Right value -> J.fromJSON value
 
 -- | Same as 'parseJsonBody', but return an invalid args response on a parse
 -- error.

yesod-json/yesod-json.cabal

@@ -7,7 +7,7 @@ maintainer:      Michael Snoyman <michael@snoyman.com>
 synopsis:        Generate content for Yesod using the aeson package.
 category:        Web, Yesod
 stability:       Stable
-cabal-version:   >= 1.6
+cabal-version:   >= 1.8
 build-type:      Simple
 homepage:        http://www.yesodweb.com/
 description:     Generate content for Yesod using the aeson package.
@@ -32,6 +32,18 @@ library
     exposed-modules: Yesod.Json
     ghc-options:     -Wall
 
+test-suite tests
+    type: exitcode-stdio-1.0
+    main-is: Spec.hs
+    hs-source-dirs: test
+    build-depends: base
+                 , wai-test
+                 , hspec
+                 , yesod-json
+                 , yesod-core
+                 , text
+                 , containers
+
 source-repository head
   type:     git
   location: https://github.com/yesodweb/yesod