Missing Accept-Encoding header should not result in compression

__tests__/index.js

@@ -245,16 +245,30 @@ describe('Compress', () => {
       .expect(200, done)
   })
 
-  it('should not crash if no accept-encoding is sent', (done) => {
+  it('should not compress if no accept-encoding is sent', (done) => {
     const app = new Koa()
-
-    app.use(compress())
-    app.use(sendBuffer)
+    app.use(compress({
+      threshold: 0
+    }))
+    app.use((ctx) => {
+      ctx.type = 'text'
+      ctx.body = buffer
+    })
     server = app.listen()
 
     request(server)
       .get('/')
-      .expect(200, done)
+      .unset('accept-encoding')
+      .end((err, res) => {
+        if (err) { return done(err) }
+
+        assert(!res.headers['content-encoding'])
+        assert(!res.headers['transfer-encoding'])
+        assert.equal(res.headers['content-length'], '1024')
+        assert.equal(res.headers.vary, 'Accept-Encoding')
+
+        done()
+      })
   })
 
   it('should not crash if a type does not pass the filter', (done) => {

lib/index.js

@@ -61,7 +61,7 @@ module.exports = (options = {}) => {
     const encodings = new Encodings({
       preferredEncodings
     })
-    encodings.parseAcceptEncoding(ctx.request.headers['accept-encoding'] || undefined)
+    encodings.parseAcceptEncoding(ctx.request.headers['accept-encoding'] || 'identity')
     const encoding = encodings.getPreferredContentEncoding()
 
     // identity === no compression