From cee0763507ed51ff75307fef2c3881b0f2f2d9e4 Mon Sep 17 00:00:00 2001
From: Erik Aker <eraker@gmail.com>
Date: Thu, 16 Jan 2020 21:22:56 -0800
Subject: [PATCH] Add an illustrative test demonstrating single question mark
 result

---
 servant-docs/test/Servant/DocsSpec.hs         | 4 +---
 servant-server/src/Servant/Server/Internal.hs | 2 +-
 servant-server/test/Servant/ServerSpec.hs     | 9 +++++++++
 3 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/servant-docs/test/Servant/DocsSpec.hs b/servant-docs/test/Servant/DocsSpec.hs
index 4d18f7e2..5c98ec32 100644
--- a/servant-docs/test/Servant/DocsSpec.hs
+++ b/servant-docs/test/Servant/DocsSpec.hs
@@ -22,8 +22,6 @@ import           Control.Monad
 import           Control.Monad.Trans.Writer
                  (Writer, runWriter, tell)
 import           Data.Aeson
-import           Data.Data
-                 (Data)
 import           Data.List
                  (isInfixOf)
 import           Data.Proxy
@@ -161,7 +159,7 @@ spec = describe "Servant.Docs" $ do
 
 data Datatype1 = Datatype1 { dt1field1 :: String
                            , dt1field2 :: Int
-                           } deriving (Eq, Show, Data, Generic)
+                           } deriving (Eq, Show, Generic)
 
 instance ToJSON Datatype1
 instance ToForm Datatype1
diff --git a/servant-server/src/Servant/Server/Internal.hs b/servant-server/src/Servant/Server/Internal.hs
index 988e4ecb..36f9f15e 100644
--- a/servant-server/src/Servant/Server/Internal.hs
+++ b/servant-server/src/Servant/Server/Internal.hs
@@ -607,7 +607,7 @@ instance
             mev :: Maybe (Either T.Text a)
             mev = case B.length rawQS of
               0 -> Nothing
-              _ -> Just $ urlDecodeAsForm (BL.drop 1 . BL.fromStrict $ rawQS)
+              _ -> Just $ urlDecodeAsForm $ BL.drop 1 $ BL.fromStrict rawQS
 
             errReq = delayedFailFatal err400
               { errBody = "Query parameter form is required"
diff --git a/servant-server/test/Servant/ServerSpec.hs b/servant-server/test/Servant/ServerSpec.hs
index e71c2015..265b2aa4 100644
--- a/servant-server/test/Servant/ServerSpec.hs
+++ b/servant-server/test/Servant/ServerSpec.hs
@@ -514,6 +514,15 @@ queryParamFormSpec = do
            }
           liftIO $ do
             decode' (simpleBody response1) `shouldBe` (Just $ Animal { species = "bimac", numberOfLegs = 7})
+      it "Just a question mark will match but return a Left" $
+        (flip runSession) (serve queryParamFormApi qpFormServer) $ do
+          let paramsQ = "?"
+          response1 <- Network.Wai.Test.request defaultRequest{
+            rawQueryString = paramsQ,
+            queryString = parseQuery paramsQ
+           }
+          liftIO $ do
+            decode' (simpleBody response1) `shouldBe` (Just $ Animal { species = "broken", numberOfLegs = 0})
       it "allows no query params at all" $
         (flip runSession) (serve queryParamFormApi qpFormServer) $ do
           response1 <- Network.Wai.Test.request defaultRequest