Added ring.util.response/charset function (fixes #67)

@@ -123,6 +123,16 @@
   [resp content-type]
   (header resp "Content-Type" content-type))
 
+(defn charset
+  "Returns an updated Ring response with the supplied charset added to the
+  Content-Type header."
+  [resp charset]
+  (update-in resp [:headers "Content-Type"]
+    (fn [content-type]
+      (-> (or content-type "text/plain")
+          (str/replace #";\s*charset=[^;]*" "")
+          (str "; charset=" charset)))))
+
 (defn set-cookie
   "Sets a cookie on the response. Requires the handler to be wrapped in the
   wrap-cookies middleware."

@@ -28,6 +28,18 @@
          (content-type {:status 200 :headers {"Content-Length" "10"}}
                        "text/html"))))
 
+(deftest test-charset
+  (testing "add charset"
+    (is (= (charset {:status 200 :headers {"Content-Type" "text/html"}} "UTF-8")
+           {:status 200 :headers {"Content-Type" "text/html; charset=UTF-8"}})))
+  (testing "replace existing charset"
+    (is (= (charset {:status 200 :headers {"Content-Type" "text/html; charset=UTF-16"}}
+                    "UTF-8")
+           {:status 200 :headers {"Content-Type" "text/html; charset=UTF-8"}})))
+  (testing "default content-type"
+    (is (= (charset {:status 200 :headers {}} "UTF-8")
+           {:status 200 :headers {"Content-Type" "text/plain; charset=UTF-8"}}))))
+
 (deftest test-header
   (is (= {:status 200 :headers {"X-Foo" "Bar"}}
          (header {:status 200 :headers {}} "X-Foo" "Bar"))))