Fix partial query-string decoding bug

This aligns Ring form parameter parsing to adhere to the encoding
scheme defined by: https://url.spec.whatwg.org/#urlencoded-parsing

Fixes #524.

Author: weavejester

ring-core/src/ring/middleware/params.clj

@@ -5,7 +5,7 @@
             [ring.util.request :as req]))
 
 (defn- parse-params [params encoding]
-  (let [params (codec/form-decode params encoding)]
+  (let [params (codec/form-decode-map params encoding)]
     (if (map? params) params {})))
 
 (defn- assoc-param-map [req k v]

ring-core/test/ring/middleware/test/params.clj

@@ -12,6 +12,11 @@
     (is (empty? (:form-params resp)))
     (is (= {"foo" "bar" "biz" "bat%"} (:params resp)))))
 
+(deftest wrap-params-partial-query-params
+  (let [req  {:query-string "foo"}
+        resp (wrapped-echo req)]
+    (is (= {"foo" ""} (:query-params resp)))))
+
 (deftest wrap-params-query-and-form-params
   (let [req  {:query-string "foo=bar"
               :headers      {"content-type" "application/x-www-form-urlencoded"}