make QueryFlag more permissive

src/Servant/API/QueryParam.hs

@@ -132,12 +132,15 @@ instance (KnownSymbol sym, HasServer sublayout)
   route Proxy subserver request respond = do
     let querytext = parseQueryText $ rawQueryString request
         param = case lookup paramname querytext of
-          Just Nothing -> True  -- param is there, with no value
-          _            -> False -- param not in the query string or with a value
+          Just Nothing  -> True  -- param is there, with no value
+          Just (Just v) -> examine v -- param with a value
+          Nothing       -> False -- param not in the query string
 
     route (Proxy :: Proxy sublayout) (subserver param) request respond
 
     where paramname = cs $ symbolVal (Proxy :: Proxy sym)
+          examine v | v == "true" || v == "1" || v == "" = True
+                    | otherwise = False
 
 instance (KnownSymbol sym, HasClient sublayout)
       => HasClient (QueryFlag sym :> sublayout) where

test/Servant/ServerSpec.hs

@@ -178,6 +178,17 @@ queryParamSpec = do
               name = "ALICE"
              }
 
+          let params3' = "?capitalize="
+          response3' <- Network.Wai.Test.request defaultRequest{
+            rawQueryString = params3',
+            queryString = parseQuery params3',
+            pathInfo = ["b"]
+           }
+          liftIO $
+            decode' (simpleBody response3') `shouldBe` Just alice{
+              name = "ALICE"
+             }
+
 type PostApi = ReqBody Person :> Post Integer
 postApi :: Proxy PostApi
 postApi = Proxy