Prefer br over gzip and deflate

index.js

@@ -45,17 +45,13 @@ var cacheControlNoTransformRegExp = /(?:^|,)\s*?no-transform\s*?(?:,|$)/
 var hasBrotliSupport = 'createBrotliCompress' in zlib
 
 var supportedEncodings = hasBrotliSupport
-  ? ['gzip', 'deflate', 'br', 'identity']
+  ? ['br', 'gzip', 'deflate', 'identity']
   : ['gzip', 'deflate', 'identity']
 
-var supportedCompressionsNoDeflate = hasBrotliSupport
-  ? ['gzip', 'br']
+var preferredEncodings = hasBrotliSupport
+  ? ['br', 'gzip']
   : ['gzip']
 
-var supportedEncodingsNoDeflate = hasBrotliSupport
-  ? ['gzip', 'br', 'identity']
-  : ['gzip', 'identity']
-
 /**
  * Compress response data with gzip / deflate.
  *
@@ -209,9 +205,14 @@ function compression (options) {
       var accept = accepts(req)
       var method = accept.encoding(supportedEncodings)
 
-      // we really don't prefer deflate
-      if (method === 'deflate' && accept.encoding(supportedCompressionsNoDeflate)) {
-        method = accept.encoding(supportedEncodingsNoDeflate)
+      // we have our own set of preferences, override user-agent preferences
+      for (var i = 0, len = preferredEncodings.length, preferred; i < len; i++) {
+        preferred = preferredEncodings[i]
+
+        if (method !== preferred && accept.encoding(preferred)) {
+          method = preferred
+          break
+        }
       }
 
       // negotiation failed

test/compression.js

@@ -532,6 +532,36 @@ describe('compression()', function () {
     })
   })
 
+  describe('when "Accept-Encoding: gzip, br"', function () {
+    var brotlit = hasBrotliSupport ? it : it.skip
+    brotlit('should respond with br', function (done) {
+      var server = createServer({ threshold: 0 }, function (req, res) {
+        res.setHeader('Content-Type', 'text/plain')
+        res.end('hello, world')
+      })
+
+      request(server)
+        .get('/')
+        .set('Accept-Encoding', 'gzip, br')
+        .expect('Content-Encoding', 'br', done)
+    })
+  })
+
+  describe('when "Accept-Encoding: deflate, gzip, br"', function () {
+    var brotlit = hasBrotliSupport ? it : it.skip
+    brotlit('should respond with br', function (done) {
+      var server = createServer({ threshold: 0 }, function (req, res) {
+        res.setHeader('Content-Type', 'text/plain')
+        res.end('hello, world')
+      })
+
+      request(server)
+        .get('/')
+        .set('Accept-Encoding', 'deflate, gzip, br')
+        .expect('Content-Encoding', 'br', done)
+    })
+  })
+
   describe('when "Accept-Encoding: deflate, br"', function () {
     var brotlit = hasBrotliSupport ? it : it.skip
     brotlit('should respond with br', function (done) {