Allow sending commands after sending an unsubscribe (#1036)

* Add test of async commands after unsubscribe

Verify that commands are handled after unsubscribing from a channel.
A command is sent before the `unsubscribe` response is received,
which currently triggers an assert in async.c:567:

`redisProcessCallbacks: Assertion `(c->flags & REDIS_SUBSCRIBED || c->flags & REDIS_MONITORING)' failed.`

* Handle async commands after an unsubscribe

When unsubscribing from the last channel we move from the `subscribe`
state to a normal state. These states uses different holders for the
command callback information.
By moving the callback info during the state change the callback order
can be maintained.

async.c

@@ -460,8 +460,15 @@ static int __redisGetSubscribeCallback(redisAsyncContext *ac, redisReply *reply,
                 /* Unset subscribed flag only when no pipelined pending subscribe. */
                 if (reply->element[2]->integer == 0
                     && dictSize(ac->sub.channels) == 0
-                    && dictSize(ac->sub.patterns) == 0)
+                    && dictSize(ac->sub.patterns) == 0) {
                     c->flags &= ~REDIS_SUBSCRIBED;
+
+                    /* Move ongoing regular command callbacks. */
+                    redisCallback cb;
+                    while (__redisShiftCallback(&ac->sub.replies,&cb) == REDIS_OK) {
+                        __redisPushCallback(&ac->replies,&cb);
+                    }
+                }
             }
         }
         sdsfree(sname);

test.c

@@ -1454,8 +1454,15 @@ typedef struct TestState {
     redisOptions *options;
     int           checkpoint;
     int           resp3;
+    int           disconnect;
 } TestState;
 
+/* Helper to disconnect and stop event loop */
+void async_disconnect(redisAsyncContext *ac) {
+    redisAsyncDisconnect(ac);
+    event_base_loopbreak(base);
+}
+
 /* Testcase timeout, will trigger a failure */
 void timeout_cb(int fd, short event, void *arg) {
     (void) fd; (void) event; (void) arg;
@@ -1480,9 +1487,18 @@ void publish_msg(redisOptions *options, const char* channel, const char* msg) {
     disconnect(c, 0);
 }
 
+/* Expect a reply of type INTEGER */
+void integer_cb(redisAsyncContext *ac, void *r, void *privdata) {
+    redisReply *reply = r;
+    TestState *state = privdata;
+    assert(reply != NULL && reply->type == REDIS_REPLY_INTEGER);
+    state->checkpoint++;
+    if (state->disconnect) async_disconnect(ac);
+}
+
 /* Subscribe callback for test_pubsub_handling and test_pubsub_handling_resp3:
  * - a published message triggers an unsubscribe
- * - an unsubscribe response triggers a disconnect */
+ * - a command is sent before the unsubscribe response is received. */
 void subscribe_cb(redisAsyncContext *ac, void *r, void *privdata) {
     redisReply *reply = r;
     TestState *state = privdata;
@@ -1505,13 +1521,13 @@ void subscribe_cb(redisAsyncContext *ac, void *r, void *privdata) {
         redisAsyncCommand(ac,unexpected_cb,
                           (void*)"unsubscribe should call subscribe_cb()",
                           "unsubscribe");
+        /* Send a regular command after unsubscribing, then disconnect */
+        state->disconnect = 1;
+        redisAsyncCommand(ac,integer_cb,state,"LPUSH mylist foo");
+
     } else if (strcmp(reply->element[0]->str,"unsubscribe") == 0) {
         assert(strcmp(reply->element[1]->str,"mychannel") == 0 &&
                reply->element[2]->str == NULL);
-
-        /* Disconnect after unsubscribe */
-        redisAsyncDisconnect(ac);
-        event_base_loopbreak(base);
     } else {
         printf("Unexpected pubsub command: %s\n", reply->element[0]->str);
         exit(1);
@@ -1520,11 +1536,11 @@ void subscribe_cb(redisAsyncContext *ac, void *r, void *privdata) {
 
 /* Expect a reply of type ARRAY */
 void array_cb(redisAsyncContext *ac, void *r, void *privdata) {
-    (void) ac;
     redisReply *reply = r;
     TestState *state = privdata;
     assert(reply != NULL && reply->type == REDIS_REPLY_ARRAY);
     state->checkpoint++;
+    if (state->disconnect) async_disconnect(ac);
 }
 
 /* Expect a NULL reply */
@@ -1565,7 +1581,7 @@ static void test_pubsub_handling(struct config config) {
     event_base_free(base);
 
     /* Verify test checkpoints */
-    assert(state.checkpoint == 2);
+    assert(state.checkpoint == 3);
 }
 
 /* Unexpected push message, will trigger a failure */
@@ -1575,15 +1591,6 @@ void unexpected_push_cb(redisAsyncContext *ac, void *r) {
     exit(1);
 }
 
-/* Expect a reply of type INTEGER */
-void integer_cb(redisAsyncContext *ac, void *r, void *privdata) {
-    (void) ac;
-    redisReply *reply = r;
-    TestState *state = privdata;
-    assert(reply != NULL && reply->type == REDIS_REPLY_INTEGER);
-    state->checkpoint++;
-}
-
 static void test_pubsub_handling_resp3(struct config config) {
     test("Subscribe, handle published message and unsubscribe using RESP3: ");
     /* Setup event dispatcher with a testcase timeout */
@@ -1624,7 +1631,7 @@ static void test_pubsub_handling_resp3(struct config config) {
     event_base_free(base);
 
     /* Verify test checkpoints */
-    assert(state.checkpoint == 5);
+    assert(state.checkpoint == 6);
 }
 
 /* Subscribe callback for test_command_timeout_during_pubsub: