Add :raw-headers option to preserve response headers verbatim

Closes dakrone#155.

Author: joelittlejohn

Readme.md

@@ -466,6 +466,28 @@ response map. This is particularly useful for paging RESTful APIs:
     :last {:href "https://api.github.com/gists?page=22884"}}
 ```
 
+### Raw headers
+By default clj-http forces lowercase header names when parsing the
+response. If you want to preserve the exact response headers (with their
+original casing), you can use the `:raw-headers` option on your request.
+When you add this option you'll receive both the usual downcased headers
+_and_ an additional map of raw headers in your response.
+
+```clojure
+(client/get "http://google.com" {:raw-headers true})
+=> {:status 200
+    :headers {"date" "Sun, 01 Aug 2010 07:03:49 GMT"
+              "cache-control" "private, max-age=0"
+              "content-type" "text/html; charset=ISO-8859-1"
+              ...}
+    :raw-headers {"Date" "Sun, 01 Aug 2010 07:03:49 GMT"
+                  "Cache-Control" "private, max-age=0"
+                  "Content-Type" "text/html; charset=ISO-8859-1"
+                  ...}
+    ...
+
+```
+
 ### Using persistent connections
 clj-http can use persistent connections to speed up connections if
 multiple connections are being used:

src/clj_http/core.clj

@@ -35,15 +35,17 @@
    If a name appears more than once (like `set-cookie`) then the value
    will be a vector containing the values in the order they appeared
    in the headers."
-  [#^HeaderIterator headers]
-  (->> (iterator-seq headers)
-       (map (fn [#^Header h] [(.toLowerCase (.getName h)) (.getValue h)]))
-       (group-by first)
-       (map (fn [[name headers]]
-              (let [values (map second headers)]
-                [name (let [[value & tail] values]
-                        (if tail values value))])))
-       (into {})))
+  ([#^HeaderIterator headers]
+      (parse-headers headers #(.toLowerCase %)))
+  ([#^HeaderIterator headers name-transform]
+      (->> (iterator-seq headers)
+           (map (fn [#^Header h] [(name-transform (.getName h)) (.getValue h)]))
+           (group-by first)
+           (map (fn [[name headers]]
+                  (let [values (map second headers)]
+                    [name (let [[value & tail] values]
+                            (if tail values value))])))
+           (into {}))))
 
 (defn set-client-param [#^HttpClient client key val]
   (when-not (nil? val)
@@ -202,7 +204,8 @@
   [{:keys [request-method scheme server-name server-port uri query-string
            headers body multipart debug debug-body socket-timeout conn-timeout
            save-request? proxy-host proxy-port as cookie-store retry-handler
-           response-interceptor digest-auth connection-manager client-params]
+           response-interceptor digest-auth connection-manager client-params
+           raw-headers]
     :as req}]
   (let [^ClientConnectionManager conn-mgr
         (or connection-manager
@@ -270,9 +273,10 @@
       (try
         (let [http-resp (.execute http-client http-req)
               http-entity (.getEntity http-resp)
-              resp {:status (.getStatusCode (.getStatusLine http-resp))
-                    :headers (parse-headers (.headerIterator http-resp))
-                    :body (coerce-body-entity req http-entity conn-mgr)}]
+              resp (merge {:status (.getStatusCode (.getStatusLine http-resp))
+                           :headers (parse-headers (.headerIterator http-resp))
+                           :body (coerce-body-entity req http-entity conn-mgr)}
+                          (if raw-headers {:raw-headers (parse-headers (.headerIterator http-resp) identity)}))]
           (if save-request?
             (-> resp
                 (assoc :request req)

test/clj_http/test/core.clj

@@ -144,7 +144,13 @@
 (deftest ^{:integration true} returns-arbitrary-headers
   (run-server)
   (let [resp (request {:request-method :get :uri "/get"})]
-    (is (string? (get-in resp [:headers "date"])))))
+    (is (string? (get-in resp [:headers "date"])))
+    (is (nil? (get-in resp [:headers "Date"])))))
+
+(deftest ^{:integration true} returns-raw-headers
+  (run-server)
+  (let [resp (request {:request-method :get :uri "/get" :raw-headers true})]
+    (is (string? (get-in resp [:raw-headers "Date"])))))
 
 (deftest ^{:integration true} returns-status-on-exceptional-responses
   (run-server)