Add functions for reading credsExtra

package.yaml

@@ -26,6 +26,7 @@ library:
     - http-types >=0.8 && <0.10
     - microlens
     - random
+    - safe
     - safe-exceptions
     - text >=0.7 && <2.0
     - transformers >=0.2.2 && <0.6

src/Yesod/Auth/OAuth2.hs

@@ -16,11 +16,20 @@ module Yesod.Auth.OAuth2
     , oauth2Url
     , authOAuth2
     , authOAuth2Widget
+
+    -- * Reading our @'credsExtra'@ keys
+    , getAccessToken
+    , getUserResponseJSON
+    , getUserResponse
     ) where
 
+import Data.Aeson (FromJSON, eitherDecode)
+import Data.ByteString.Lazy (ByteString, fromStrict)
 import Data.Text (Text)
+import Data.Text.Encoding (encodeUtf8)
 import Network.HTTP.Conduit (Manager)
 import Network.OAuth.OAuth2
+import Safe (fromJustNote)
 import Yesod.Auth
 import Yesod.Auth.OAuth2.Dispatch
 import Yesod.Core.Widget
@@ -51,3 +60,29 @@ authOAuth2Widget widget name oauth getCreds =
     AuthPlugin name (dispatchAuthRequest name oauth getCreds) login
   where
     login tm = [whamlet|<a href=@{tm $ oauth2Url name}>^{widget}|]
+
+-- | Read from the values set via @'setExtra'@
+--
+-- This is unsafe.
+--
+getAccessToken :: Creds m -> AccessToken
+getAccessToken = AccessToken
+    . fromJustNote "yesod-auth-oauth2 bug: credsExtra without accessToken"
+    . lookup "accessToken" . credsExtra
+
+-- | Read from the values set via @'setExtra'@
+--
+-- This is unsafe.
+--
+getUserResponseJSON :: Creds m -> ByteString
+getUserResponseJSON = fromStrict . encodeUtf8
+    . fromJustNote "yesod-auth-oauth2 bug: credsExtra without userResponseJSON"
+    . lookup "userResponseJSON" . credsExtra
+
+-- | Read from the values set via @'setExtra'@
+--
+-- This is unsafe if the key is missing, but safe with respect to parsing
+-- errors.
+--
+getUserResponse :: FromJSON a => Creds m -> Either String a
+getUserResponse = eitherDecode . getUserResponseJSON