feat(pubsub):implement PUBSUB NUMPAT

Fix #195

fakeredis/commands_mixins/pubsub_mixin.py

@@ -73,6 +73,10 @@ def publish(self, channel, message):
                     receivers += 1
         return receivers
 
+    @command(name='PUBSUB NUMPAT', fixed=(), repeat=())
+    def pubsub_numpat(self, *_):
+        return len(self._server.psubscribers)
+
     @command(name='PUBSUB CHANNELS', fixed=(), repeat=(bytes,))
     def pubsub_channels(self, *args):
         channels = list(self._server.subscribers.keys())

test/test_mixins/test_pubsub_commands.py

@@ -1,16 +1,33 @@
 import threading
+import time
 import uuid
 from queue import Queue
 from time import sleep
+from typing import Optional, Dict, Any
 
 import pytest
 import redis
+from redis.client import PubSub
 
 import fakeredis
 from .. import testtools
 from ..testtools import raw_command
 
 
+def wait_for_message(
+        pubsub: PubSub, timeout=0.5, ignore_subscribe_messages=False
+) -> Optional[Dict[str, Any]]:
+    now = time.time()
+    timeout = now + timeout
+    while now < timeout:
+        message = pubsub.get_message(ignore_subscribe_messages=ignore_subscribe_messages)
+        if message is not None:
+            return message
+        time.sleep(0.01)
+        now = time.time()
+    return None
+
+
 def test_ping_pubsub(r: redis.Redis):
     p = r.pubsub()
     p.subscribe('channel')
@@ -40,6 +57,15 @@ def test_pubsub_subscribe(r: redis.Redis):
     assert message == expected_message
 
 
+@pytest.mark.slow
+def test_pubsub_numpat(r: redis.Redis):
+    p = r.pubsub()
+    p.psubscribe("*oo", "*ar", "b*z")
+    for i in range(3):
+        assert wait_for_message(p)["type"] == "psubscribe"
+    assert r.pubsub_numpat() == 3
+
+
 @pytest.mark.slow
 def test_pubsub_psubscribe(r: redis.Redis):
     pubsub = r.pubsub()