Preventing NPE on decode-body-headers when body is nil (e.g. HEAD request)

README.org

@@ -387,6 +387,8 @@ from clj-http's dependencies without causing any problems like so:
                  [clj-http "0.6.0" :exclusions [crouton]]])
 #+END_SRC
 
+Note also that HEAD requests will not return a body, in which case this setting will have no effect.
+
 clj-http will automatically disable the =:decode-body-headers= option.
 
 ** Misc

src/clj_http/client.clj

@@ -488,22 +488,20 @@
   web page, adding them into the headers map of the response if any
   are found. Only looks at the body if the :decode-body-headers option
   is set to a truthy value. Will be silently disabled if crouton is excluded
-  from clj-http's dependencies."
+  from clj-http's dependencies. Will do nothing if no body is returned, e.g. HEAD requests"
   [client]
   (fn [req]
-    (if (opt req :decode-body-headers)
-      (if crouton-enabled?
-        (let [resp (client req)
-              body-bytes (util/force-byte-array (:body resp))
+    (let [resp (client req)]
+      (if (and (opt req :decode-body-headers) crouton-enabled? (:body resp))
+        (let [body-bytes (util/force-byte-array (:body resp))
               body-stream1 (java.io.ByteArrayInputStream. body-bytes)
               body-map (parse-html body-stream1)
               additional-headers (get-headers-from-body body-map)
               body-stream2 (java.io.ByteArrayInputStream. body-bytes)]
           (assoc resp
-                 :headers (merge (:headers resp) additional-headers)
-                 :body body-stream2))
-        (client req))
-      (client req))))
+            :headers (merge (:headers resp) additional-headers)
+            :body body-stream2))
+        resp))))
 
 (defn content-type-value [type]
   (if (keyword? type)

test/clj_http/test/client.clj

@@ -635,12 +635,14 @@
         client (fn [req] {:body (.getBytes text)})
         new-client (client/wrap-additional-header-parsing client)
         resp (new-client {:decode-body-headers true})
-        resp2 (new-client {:decode-body-headers false})]
+        resp2 (new-client {:decode-body-headers false})
+        resp3 ((client/wrap-additional-header-parsing (fn [req] {:body nil})) {:decode-body-headers true})]
     (is (= {"content-type" "text/html; charset=Shift_JIS"
             "content-style-type" "text/css"
             "content-script-type" "text/javascript"}
            (:headers resp)))
-    (is (nil? (:headers resp2)))))
+    (is (nil? (:headers resp2)))
+    (is (nil? (:headers resp3)))))
 
 (deftest t-wrap-additional-header-parsing-html5
   (let [^String text (slurp (resource "header-html5-test.html"))