From 1fba9dc6048cea6184964032b861b052cd54878c Mon Sep 17 00:00:00 2001
From: Ian Shipman <22924983+GambolingPangolin@users.noreply.github.com>
Date: Mon, 16 May 2022 09:50:10 -0500
Subject: [PATCH] Only add a ? when query string is nonempty (#1589)

* Only add a ? when query string is nonempty

* Adds changelog entry
---
 changelog.d/1589                                         | 2 ++
 servant-client/src/Servant/Client/Internal/HttpClient.hs | 3 ++-
 2 files changed, 4 insertions(+), 1 deletion(-)
 create mode 100644 changelog.d/1589

diff --git a/changelog.d/1589 b/changelog.d/1589
new file mode 100644
index 00000000..5f477b79
--- /dev/null
+++ b/changelog.d/1589
@@ -0,0 +1,2 @@
+synopsis: Only include question mark for nonempty query strings
+prs: 1589
diff --git a/servant-client/src/Servant/Client/Internal/HttpClient.hs b/servant-client/src/Servant/Client/Internal/HttpClient.hs
index 42fecfb7..ee146cc7 100644
--- a/servant-client/src/Servant/Client/Internal/HttpClient.hs
+++ b/servant-client/src/Servant/Client/Internal/HttpClient.hs
@@ -289,7 +289,8 @@ defaultMakeClientRequest burl r = Client.defaultRequest
         Https -> True
 
     -- Query string builder which does not do any encoding
-    buildQueryString = ("?" <>) . foldl' addQueryParam mempty
+    buildQueryString [] = mempty
+    buildQueryString qps = "?" <> foldl' addQueryParam mempty qps
 
     addQueryParam qs (k, v) =
           qs <> (if BS.null qs then mempty else "&") <> urlEncode True k <> foldMap ("=" <>) v