refactor: simplify encoding negotiation logic

Author: bjohansebas

index.js

@@ -44,8 +44,6 @@ var cacheControlNoTransformRegExp = /(?:^|,)\s*?no-transform\s*?(?:,|$)/
 var SUPPORTED_ENCODING = hasBrotliSupport ? ['br', 'gzip', 'deflate', 'identity'] : ['gzip', 'deflate', 'identity']
 var PREFERRED_ENCODING = hasBrotliSupport ? ['br', 'gzip'] : ['gzip']
 
-var encodingSupported = ['*', 'gzip', 'deflate', 'identity', 'br']
-
 /**
  * Compress response data with gzip / deflate.
  *
@@ -195,14 +193,9 @@ function compression (options) {
       }
 
       // compression method
-      var negotiator = new Negotiator(req)
+      var negotiator = new Negotiator({ headers: req.headers['accept-encoding'] ? req.headers : { 'accept-encoding': enforceEncoding } })
       var method = negotiator.encoding(SUPPORTED_ENCODING, PREFERRED_ENCODING)
 
-      // if no method is found, use the default encoding
-      if (!req.headers['accept-encoding'] && encodingSupported.indexOf(enforceEncoding) !== -1) {
-        method = enforceEncoding === '*' ? 'gzip' : enforceEncoding
-      }
-
       // negotiation failed
       if (!method || method === 'identity') {
         nocompress('not acceptable')

test/compression.js

@@ -969,8 +969,8 @@ describe('compression()', function () {
       request(server)
         .get('/')
         .set('Accept-Encoding', '')
-        .expect('Content-Encoding', 'gzip')
-        .expect(200, 'hello, world', done)
+        .expect('Content-Encoding', 'br')
+        .expect(200, done)
     })
   })
 })