req.acceptsEncodings: default to 'identity'

docs/api/request.md

@@ -224,7 +224,7 @@ switch (this.accepts('json', 'html', 'text')) {
 ### req.acceptsEncodings(encodings)
 
   Check if `encodings` are acceptable, returning
-  the best match when true, otherwise `undefined`.
+  the best match when true, otherwise `identity`.
 
 ```js
 // Accept-Encoding: gzip

lib/request.js

@@ -428,7 +428,7 @@ module.exports = {
     if (!Array.isArray(encodings)) encodings = [].slice.call(arguments);
     var n = new Negotiator(this.req);
     if (!encodings.length) return n.preferredEncodings();
-    return n.preferredEncodings(encodings)[0];
+    return n.preferredEncodings(encodings)[0] || 'identity';
   },
 
   /**

test/request/acceptsEncodings.js

@@ -8,6 +8,7 @@ describe('ctx.acceptsEncodings()', function(){
         var ctx = context();
         ctx.req.headers['accept-encoding'] = 'gzip, compress;q=0.2';
         ctx.acceptsEncodings().should.eql(['gzip', 'compress', 'identity']);
+        ctx.acceptsEncodings('gzip', 'compress').should.equal('gzip');
       })
     })
 
@@ -15,6 +16,7 @@ describe('ctx.acceptsEncodings()', function(){
       it('should return identity', function(){
         var ctx = context();
         ctx.acceptsEncodings().should.eql(['identity']);
+        ctx.acceptsEncodings('gzip', 'deflate').should.equal('identity');
       })
     })
   })