Adding option to disable automatic decompression (#2661)

* Adding ability to disable auto decompression

* Updating decompress documentation in README

* Fixing test\unit\adapters\http.js lint errors

* Adding test for disabling auto decompression

* Removing changes that fixed lint errors in tests

* Removing formating change to unit test

Co-authored-by: Xianming Zhong <chinesedfan@qq.com>

lib/adapters/http.js

@@ -181,20 +181,25 @@ module.exports = function httpAdapter(config) {
 
       // uncompress the response body transparently if required
       var stream = res;
+
       // return the last request in case of redirects
       var lastRequest = res.req || req;
 
-      switch (res.headers['content-encoding']) {
-      /*eslint default-case:0*/
-      case 'gzip':
-      case 'compress':
-      case 'deflate':
-        // add the unzipper to the body stream processing pipeline
-        stream = (res.statusCode === 204 || lastRequest.method === 'HEAD') ? stream : stream.pipe(zlib.createUnzip());
 
-        // remove the content-encoding in order to not confuse downstream operations
-        delete res.headers['content-encoding'];
-        break;
+      // if no content, is HEAD request or decompress disabled we should not decompress
+      if (res.statusCode !== 204 && lastRequest.method !== 'HEAD' && config.decompress !== false) {
+        switch (res.headers['content-encoding']) {
+        /*eslint default-case:0*/
+        case 'gzip':
+        case 'compress':
+        case 'deflate':
+        // add the unzipper to the body stream processing pipeline
+          stream = stream.pipe(zlib.createUnzip());
+
+          // remove the content-encoding in order to not confuse downstream operations
+          delete res.headers['content-encoding'];
+          break;
+        }
       }
 
       var response = {