Fix behavior of null/undefined as "maxAge" in res.cookie

fixes #3935
closes #3936

History.md

@@ -4,6 +4,7 @@ unreleased
   * Add "root" option to `res.download`
   * Allow `options` without `filename` in `res.download`
   * Deprecate string and non-integer arguments to `res.status`
+  * Fix behavior of `null`/`undefined` as `maxAge` in `res.cookie`
   * Ignore `Object.prototype` values in settings through `app.set`/`app.get`
   * Invoke `default` with same arguments as types in `res.format`
   * Support proper 205 responses using `res.send`

lib/response.js

@@ -868,9 +868,13 @@ res.cookie = function (name, value, options) {
     val = 's:' + sign(val, secret);
   }
 
-  if ('maxAge' in opts) {
+  if (opts.maxAge != null) {
-    opts.expires = new Date(Date.now() + opts.maxAge);
+    var maxAge = opts.maxAge - 0
-    opts.maxAge /= 1000;
+
+    if (!isNaN(maxAge)) {
+      opts.expires = new Date(Date.now() + maxAge)
+      opts.maxAge = Math.floor(maxAge / 1000)
+    }
   }
 
   if (opts.path == null) {

test/res.cookie.js

@@ -111,6 +111,36 @@ describe('res', function(){
         .expect(200, optionsCopy, done)
       })
 
+      it('should not throw on null', function (done) {
+        var app = express()
+
+        app.use(function (req, res) {
+          res.cookie('name', 'tobi', { maxAge: null })
+          res.end()
+        })
+
+        request(app)
+          .get('/')
+          .expect(200)
+          .expect('Set-Cookie', 'name=tobi; Path=/')
+          .end(done)
+      })
+
+      it('should not throw on undefined', function (done) {
+        var app = express()
+
+        app.use(function (req, res) {
+          res.cookie('name', 'tobi', { maxAge: undefined })
+          res.end()
+        })
+
+        request(app)
+          .get('/')
+          .expect(200)
+          .expect('Set-Cookie', 'name=tobi; Path=/')
+          .end(done)
+      })
+
       it('should throw an error with invalid maxAge', function (done) {
         var app = express()