fix(client): Handle multiple layers of compression

src/clj_http/client.clj

@@ -386,14 +386,12 @@
   [resp]
   (-> resp
       (update :body util/gunzip)
-      (assoc :orig-content-encoding (get-in resp [:headers "content-encoding"]))
       (dissoc-in [:headers "content-encoding"])))
 
 (defmethod decompress-body "deflate"
   [resp]
   (-> resp
       (update :body util/inflate)
-      (assoc :orig-content-encoding (get-in resp [:headers "content-encoding"]))
       (dissoc-in [:headers "content-encoding"])))
 
 (defmethod decompress-body :default [resp]
@@ -412,7 +410,34 @@
   [req resp]
   (if (false? (opt req :decompress-body))
     resp
-    (decompress-body resp)))
+    ;; If we are decompressing the body there might be multiple content
+    ;; encodings.
+    ;; https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Encoding
+    ;; Take each content encoding (in reverse order) and try to decompress the
+    ;; body using that content encording recursively. This way if content is
+    ;; compressed twice. Once with zlib and again with gzip, then we can
+    ;; properly decompress it in the correct order.
+    (loop [[encoding & rest-encodings] (some-> resp
+                                               (get-in [:headers "content-encoding"])
+                                               (str/split #",")
+                                               (reverse))
+           ;; Store the original content encoding somewhere so it can be
+           ;; referenced if needed.
+           resp (assoc resp
+                       :orig-content-encoding
+                       (get-in resp [:headers "content-encoding"]))]
+      (if encoding
+        ;; If there is an encoding then decompress the body using that encoding
+        ;; then recur with the remaining encodings.
+        (recur
+         rest-encodings
+         (decompress-body
+           ;; Force the content encoding to be a single encoding type for this.
+          (assoc-in resp
+                    [:headers "content-encoding"]
+                    (str/trim encoding))))
+        ;; If there are no encodings left then we are done.
+        resp))))
 
 (defn wrap-decompression
   "Middleware handling automatic decompression of responses from web servers. If

test/clj_http/test/client_test.clj

@@ -694,6 +694,20 @@
     (is (= "gzip" (:orig-content-encoding resp)))
     (is (= nil (get-in resp [:headers "content-encoding"])))))
 
+(deftest apply-on-compressed-layered
+  (let [client (fn [req]
+                 (is (= "gzip, deflate"
+                        (get-in req [:headers "accept-encoding"])))
+                 {:body (util/gzip (util/deflate (util/utf8-bytes "foofoofoo")))
+                  :headers {"content-encoding" "deflate, gzip"}})
+        c-client (client/wrap-decompression client)
+        resp (c-client {})]
+    ;; The response body here is going to be an input stream because of the
+    ;; nesting. So we need to slurp it, or force it to be a string of some sort.
+    (is (= "foofoofoo" (slurp (:body resp))))
+    (is (= "deflate, gzip" (:orig-content-encoding resp)))
+    (is (= nil (get-in resp [:headers "content-encoding"])))))
+
 (deftest apply-on-compressed-async
   (let [client (fn [req respond raise]
                  (is (= "gzip, deflate"