From e8bae7d03561208f9d5e6def541ef932ca8264e7 Mon Sep 17 00:00:00 2001
From: Alp Mestanogullari <alpmestan@gmail.com>
Date: Thu, 18 Jun 2015 18:03:48 +0200
Subject: [PATCH 1/4] Tweak the HasLink instance for QueryParam, fixes #129

---
 servant/src/Servant/Utils/Links.hs | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/servant/src/Servant/Utils/Links.hs b/servant/src/Servant/Utils/Links.hs
index 15f38096..ec6ebbd6 100644
--- a/servant/src/Servant/Utils/Links.hs
+++ b/servant/src/Servant/Utils/Links.hs
@@ -273,10 +273,10 @@ instance (KnownSymbol sym, HasLink sub) => HasLink (sym :> sub) where
 -- QueryParam instances
 instance (KnownSymbol sym, ToText v, HasLink sub)
     => HasLink (QueryParam sym v :> sub) where
-    type MkLink (QueryParam sym v :> sub) = v -> MkLink sub
-    toLink _ l v =
-        toLink (Proxy :: Proxy sub)
-             (addQueryParam (SingleParam k (toText v)) l)
+    type MkLink (QueryParam sym v :> sub) = Maybe v -> MkLink sub
+    toLink _ l mv =
+        toLink (Proxy :: Proxy sub) $
+            maybe id (addQueryParam . SingleParam k . toText) mv l
       where
         k :: String
         k = symbolVal (Proxy :: Proxy sym)

From 9fbd312b4c707d73fefb77eb6724767f4a4d0623 Mon Sep 17 00:00:00 2001
From: Alp Mestanogullari <alpmestan@gmail.com>
Date: Fri, 19 Jun 2015 10:03:24 +0200
Subject: [PATCH 2/4] adapt tests to the modified HasLink instance for
 QueryParam

---
 servant/test/Servant/Utils/LinksSpec.hs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/servant/test/Servant/Utils/LinksSpec.hs b/servant/test/Servant/Utils/LinksSpec.hs
index 0fa17b3a..b261559e 100644
--- a/servant/test/Servant/Utils/LinksSpec.hs
+++ b/servant/test/Servant/Utils/LinksSpec.hs
@@ -61,7 +61,7 @@ spec = describe "Servant.Utils.Links" $ do
         let l2 = Proxy :: Proxy ("hello" :> Capture "name" String
                                          :> QueryParam "capital" Bool
                                          :> Delete '[JSON] ())
-        apiLink l2 "bye" True `shouldBeURI` "hello/bye?capital=true"
+        apiLink l2 "bye" (Just True) `shouldBeURI` "hello/bye?capital=true"
 
         let l3 = Proxy :: Proxy ("parent" :> MatrixParams "name" String
                                           :> "child"

From 82328247e693b97f822d5fb56095f0ac20b064e3 Mon Sep 17 00:00:00 2001
From: Alp Mestanogullari <alpmestan@gmail.com>
Date: Fri, 19 Jun 2015 10:29:06 +0200
Subject: [PATCH 3/4] Fix doctests for Link/QueryParam

---
 servant/src/Servant/Utils/Links.hs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/servant/src/Servant/Utils/Links.hs b/servant/src/Servant/Utils/Links.hs
index ec6ebbd6..5fa8bd0b 100644
--- a/servant/src/Servant/Utils/Links.hs
+++ b/servant/src/Servant/Utils/Links.hs
@@ -49,7 +49,7 @@
 -- or without those:
 --
 -- >>> let with = Proxy :: Proxy ("bye" :> QueryParam "name" String :> Delete '[JSON] ())
--- >>> print $ safeLink api with "Hubert"
+-- >>> print $ safeLink api with (Just "Hubert")
 -- bye?name=Hubert
 --
 -- >>> let without = Proxy :: Proxy ("bye" :> Delete '[JSON] ())

From 0e22d19800514f14ca838257b2debb809e7ef939 Mon Sep 17 00:00:00 2001
From: Alp Mestanogullari <alpmestan@gmail.com>
Date: Fri, 19 Jun 2015 11:30:44 +0200
Subject: [PATCH 4/4] Make Link take a Maybe argument for MatrixParam, just
 like QueryParam

---
 servant/src/Servant/Utils/Links.hs      | 6 +++---
 servant/test/Servant/Utils/LinksSpec.hs | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/servant/src/Servant/Utils/Links.hs b/servant/src/Servant/Utils/Links.hs
index 5fa8bd0b..19fdc019 100644
--- a/servant/src/Servant/Utils/Links.hs
+++ b/servant/src/Servant/Utils/Links.hs
@@ -303,10 +303,10 @@ instance (KnownSymbol sym, HasLink sub)
 -- MatrixParam instances
 instance (KnownSymbol sym, ToText v, HasLink sub)
     => HasLink (MatrixParam sym v :> sub) where
-    type MkLink (MatrixParam sym v :> sub) = v -> MkLink sub
-    toLink _ l v =
+    type MkLink (MatrixParam sym v :> sub) = Maybe v -> MkLink sub
+    toLink _ l mv =
         toLink (Proxy :: Proxy sub) $
-            addMatrixParam (SingleParam k (toText v)) l
+            maybe id (addMatrixParam . SingleParam k . toText) mv l
       where
         k = symbolVal (Proxy :: Proxy sym)
 
diff --git a/servant/test/Servant/Utils/LinksSpec.hs b/servant/test/Servant/Utils/LinksSpec.hs
index b261559e..16f13925 100644
--- a/servant/test/Servant/Utils/LinksSpec.hs
+++ b/servant/test/Servant/Utils/LinksSpec.hs
@@ -67,7 +67,7 @@ spec = describe "Servant.Utils.Links" $ do
                                           :> "child"
                                           :> MatrixParam "gender" String
                                           :> Get '[JSON] String)
-        apiLink l3 ["Hubert?x=;&", "Cumberdale"] "Edward?"
+        apiLink l3 ["Hubert?x=;&", "Cumberdale"] (Just "Edward?")
             `shouldBeURI` "parent;name[]=Hubert%3Fx%3D%3B%26;\
                            \name[]=Cumberdale/child;gender=Edward%3F"