Delete key if resulting TTL is negative in set method. (#321)

If the set method is invoked with a session object which has a cookie
that expires in the past then the key is deleted / destroyed. Otherwise,
a negative TTL is calculated and that leads to Redis throwing an error
'ERR invalid expire time in set'.

lib/connect-redis.js

@@ -54,9 +54,19 @@ module.exports = function (session) {
         return cb(er)
       }
       args.push(value)
-      if (!this.disableTTL) args.push('EX', this._getTTL(sess))
 
-      this.client.set(args, cb)
+      let ttl = 1
+      if (!this.disableTTL) {
+        ttl = this._getTTL(sess)
+        args.push('EX', ttl)
+      }
+
+      if (ttl > 0) {
+        this.client.set(args, cb)
+      } else {
+        // If the resulting TTL is negative we can delete / destroy the key
+        this.destroy(sid, cb)
+      }
     }
 
     touch(sid, sess, cb = noop) {

test/connect-redis-test.js

@@ -120,6 +120,20 @@ async function lifecycleTest(store, t) {
 
   res = await p(store, 'clear')()
   t.equal(res, count, 'bulk clear')
+
+  expires = new Date(Date.now() + ttl * 1000).toISOString() // expires in the future
+  res = await p(store, 'set')('789', { cookie: { expires } })
+  t.equal(res, 'OK', 'set value')
+
+  res = await p(store, 'length')()
+  t.equal(res, 1, 'one key exists (session 789)')
+
+  expires = new Date(Date.now() - ttl * 1000).toISOString() // expires in the past
+  res = await p(store, 'set')('789', { cookie: { expires } })
+  t.equal(res, 1, 'returns 1 because destroy was invoked')
+
+  res = await p(store, 'length')()
+  t.equal(res, 0, 'no key remains and that includes session 789')
 }
 
 function load(store, count) {