Replace call to error with throwIO. Fixes #2

* error would crash the server
* IO exception should result in a 500

Yesod/Auth/OAuth2.hs

@@ -1,4 +1,6 @@
-{-# LANGUAGE OverloadedStrings, QuasiQuotes #-}
+{-# LANGUAGE DeriveDataTypeable #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE QuasiQuotes #-}
 -- |
 --
 -- Generic OAuth2 plugin for Yesod
@@ -8,19 +10,31 @@
 module Yesod.Auth.OAuth2
     ( authOAuth2
     , oauth2Url
+    , YesodOAuth2Exception(..)
     , module Network.OAuth.OAuth2
     ) where
 
+import Control.Exception.Lifted
 import Control.Monad.IO.Class
 import Data.ByteString (ByteString)
 import Data.Text (Text)
 import Data.Text.Encoding (decodeUtf8With, encodeUtf8)
 import Data.Text.Encoding.Error (lenientDecode)
+import Data.Typeable
 import Network.OAuth.OAuth2
 import Yesod.Auth
 import Yesod.Core
 import Yesod.Form
 
+import qualified Data.ByteString.Lazy as BSL
+
+data YesodOAuth2Exception = InvalidProfileResponse
+    Text           -- ^ Provider name
+    BSL.ByteString -- ^ Aeson parse error
+    deriving (Show, Typeable)
+
+instance Exception YesodOAuth2Exception
+
 oauth2Url :: Text -> AuthRoute
 oauth2Url name = PluginR name ["forward"]
 

Yesod/Auth/OAuth2/Learn.hs

@@ -13,6 +13,7 @@ module Yesod.Auth.OAuth2.Learn
     ) where
 
 import Control.Applicative ((<$>), (<*>))
+import Control.Exception.Lifted
 import Control.Monad (mzero)
 import Data.Aeson
 import Data.Text (Text)
@@ -65,7 +66,7 @@ fetchLearnProfile token = do
 
     case result of
         Right (LearnResponse user) -> return $ toCreds user
-        _ -> error "Invalid response for learn profile data"
+        Left err -> throwIO $ InvalidProfileResponse "learn" err
 
 toCreds :: LearnUser -> Creds m
 toCreds user = Creds "learn"

yesod-auth-oauth2.cabal

@@ -31,6 +31,7 @@ library
                    , yesod-form              >= 1.3       && < 1.4
                    , transformers            >= 0.2.2     && < 0.4
                    , hoauth2                 >= 0.3.6     && < 0.4
+                   , lifted-base             >= 0.2.2     && < 0.4
 
     exposed-modules: Yesod.Auth.OAuth2
                      Yesod.Auth.OAuth2.Google