disconnect on reconnect() if connected

fixes #243

Author: vladak

adafruit_minimqtt/adafruit_minimqtt.py

@@ -939,11 +939,18 @@ def reconnect(self, resub_topics: bool = True) -> int:
         """
 
         self.logger.debug("Attempting to reconnect with MQTT broker")
+        subscribed_topics = []
+        if self.is_connected():
+            # disconnect() will reset subscribed topics so stash them now.
+            if resub_topics:
+                subscribed_topics = self._subscribed_topics.copy()
+            self.disconnect()
+
         ret = self.connect()
         self.logger.debug("Reconnected with broker")
-        if resub_topics:
+
+        if resub_topics and subscribed_topics:
             self.logger.debug("Attempting to resubscribe to previously subscribed topics.")
-            subscribed_topics = self._subscribed_topics.copy()
             self._subscribed_topics = []
             while subscribed_topics:
                 feed = subscribed_topics.pop()

tests/test_reconnect.py

@@ -0,0 +1,205 @@
+# SPDX-FileCopyrightText: 2025 Vladimír Kotal
+#
+# SPDX-License-Identifier: Unlicense
+
+"""reconnect tests"""
+
+import logging
+import ssl
+import sys
+
+import pytest
+from mocket import Mocket
+
+import adafruit_minimqtt.adafruit_minimqtt as MQTT
+
+if not sys.implementation.name == "circuitpython":
+    from typing import Optional
+
+    from circuitpython_typing.socket import (
+        SocketType,
+        SSLContextType,
+    )
+
+
+class FakeConnectionManager:
+    """
+    Fake ConnectionManager class
+    """
+
+    def __init__(self, socket):
+        self._socket = socket
+
+    def get_socket(  # noqa: PLR0913, Too many arguments
+        self,
+        host: str,
+        port: int,
+        proto: str,
+        session_id: Optional[str] = None,
+        *,
+        timeout: float = 1.0,
+        is_ssl: bool = False,
+        ssl_context: Optional[SSLContextType] = None,
+    ) -> SocketType:
+        """
+        Return the specified socket.
+        """
+        return self._socket
+
+    def close_socket(self, socket) -> None:
+        pass
+
+
+def handle_subscribe(client, user_data, topic, qos):
+    """
+    Record topics into user data.
+    """
+    assert topic
+    assert user_data["topics"] is not None
+    assert qos == 0
+
+    user_data["topics"].append(topic)
+
+
+def handle_disconnect(client, user_data, zero):
+    """
+    Record disconnect.
+    """
+
+    user_data["disconnect"] = True
+
+
+# The MQTT packet contents below were captured using Mosquitto client+server.
+testdata = [
+    (
+        [],
+        bytearray(
+            [
+                0x20,  # CONNACK
+                0x02,
+                0x00,
+                0x00,
+                0x90,  # SUBACK
+                0x03,
+                0x00,
+                0x01,
+                0x00,
+                0x20,  # CONNACK
+                0x02,
+                0x00,
+                0x00,
+                0x90,  # SUBACK
+                0x03,
+                0x00,
+                0x02,
+                0x00,
+            ]
+        ),
+    ),
+    (
+        [("foo/bar", 0)],
+        bytearray(
+            [
+                0x20,  # CONNACK
+                0x02,
+                0x00,
+                0x00,
+                0x90,  # SUBACK
+                0x03,
+                0x00,
+                0x01,
+                0x00,
+                0x20,  # CONNACK
+                0x02,
+                0x00,
+                0x00,
+                0x90,  # SUBACK
+                0x03,
+                0x00,
+                0x02,
+                0x00,
+            ]
+        ),
+    ),
+    (
+        [("foo/bar", 0), ("bah", 0)],
+        bytearray(
+            [
+                0x20,  # CONNACK
+                0x02,
+                0x00,
+                0x00,
+                0x90,  # SUBACK
+                0x03,
+                0x00,
+                0x01,
+                0x00,
+                0x00,
+                0x20,  # CONNACK
+                0x02,
+                0x00,
+                0x00,
+                0x90,  # SUBACK
+                0x03,
+                0x00,
+                0x02,
+                0x00,
+                0x90,  # SUBACK
+                0x03,
+                0x00,
+                0x03,
+                0x00,
+            ]
+        ),
+    ),
+]
+
+
+@pytest.mark.parametrize(
+    "topics,to_send",
+    testdata,
+    ids=[
+        "no_topic",
+        "single_topic",
+        "multi_topic",
+    ],
+)
+def test_reconnect(topics, to_send) -> None:
+    """
+    Test reconnect() handling, mainly that it performs disconnect on already connected socket.
+
+    Nothing will travel over the wire, it is all fake.
+    """
+    logging.basicConfig()
+    logger = logging.getLogger(__name__)
+    logger.setLevel(logging.DEBUG)
+
+    host = "localhost"
+    port = 1883
+
+    user_data = {"topics": [], "disconnect": False}
+    mqtt_client = MQTT.MQTT(
+        broker=host,
+        port=port,
+        ssl_context=ssl.create_default_context(),
+        connect_retries=1,
+        user_data=user_data,
+    )
+
+    mocket = Mocket(to_send)
+    mqtt_client._connection_manager = FakeConnectionManager(mocket)
+    mqtt_client.connect()
+
+    mqtt_client.logger = logger
+
+    if topics:
+        logger.info(f"subscribing to {topics}")
+        mqtt_client.subscribe(topics)
+
+    logger.info("reconnecting")
+    mqtt_client.on_subscribe = handle_subscribe
+    mqtt_client.on_disconnect = handle_disconnect
+    mqtt_client.reconnect()
+
+    assert user_data.get("disconnect") == True
+    assert set(user_data.get("topics")) == set([t[0] for t in topics])