Post 🚀 New issue to faststream-community/zMQTT by @borisalekseev

🚀 New issue to faststream-community/zMQTT by @borisalekseev 📝 MQTT 5 publish() silently succeeds when PUBACK or PUBREC rejects the message (#65) Summary MQTTClient.publish() returns normally when an MQTT 5 broker rejects a QoS 1 or QoS 2 PUBLISH with a negative acknowledgement reason code. For example, Mosquitto returns 0x87 (Not authorized) for an ACL-denied publication: Received PubAck(packet_id=1, reason_code=135, properties=None) The message was not accepted by the broker, but await client.publish(...) completes without an exception. Current behavior For QoS 1, _handle_puback() resolves the publish future successfully without checking PubAck.reason_code. For QoS 2, _handle_pubrec() also ignores the reason code and sends PUBREL even when PUBREC contains 0x87. MQTT 5 only permits PUBREL after a PUBREC reason code below 0x80. The public MQTTClient.publish() method discards the acknowledgement returned by MQTTProtocol.publish(). Expected behavior • PUBACK/PUBREC reason codes below 0x80, including 0x00 and 0x10 (No matching subscribers), complete successfully. • A PUBACK or PUBREC reason code of 0x80 or greater raises a public MQTTPublishError. • The exception exposes at least reason_code; exposing the optional Reason String would also be useful. • A negative PUBREC completes and removes the QoS 2 flight, releases its packet identifier, and does not send PUBREL. • The MQTT connection remains usable after the rejected operation. • MQTT 3.1.1 behavior remains unchanged because PUBACK and PUBREC do not carry reason codes in that protocol version. MQTTPublishError would be consistent with the existing MQTTSubscribeError. Protocol references • MQTT 5.0 section 2.4: reason codes 0x80 and greater indicate failure. • MQTT 5.0 section 3.4.2.1: PUBACK 0x87 means the PUBLISH is not authorized. • MQTT 5.0 section 3.5.2.1: PUBREC has the same publish-rejection reason codes. • MQTT 5.0 section 4.3.3: PUBREL is sent only after a PUBREC reason code below 0x80. • MQTT 5.0 section 4.4: a negative PUBACK/PUBREC acknowledges the packet for retry purposes, but does not make the publication successful. • MQTT 3.1.1 section 3.3.5: when a PUBLISH is not authorized, the server must either send a positive acknowledgement or close the connection because the protocol has no negative publish acknowledgement. Reproduction result Reproduced with Mosquitto 2.1.2 and a read-only ACL: MQTT 5 QoS 1: Received PubAck(packet_id=1, reason_code=135, properties=None) publish() returned normally MQTT 5 QoS 2: Received PubRec(packet_id=1, reason_code=135, properties=None) QoS 2 PUBREC received, sent PUBREL publish() returned normally Mosquitto logs Denied PUBLISH for both messages. Suggested tests • QoS 1 negative PUBACK raises and releases the packet identifier. • QoS 1 0x10 completes successfully. • QoS 2 negative PUBREC raises, releases the packet identifier, and sends no PUBREL. • Optional Reason String is preserved in the exception. • MQTT 3.1.1 ACK behavior is unchanged. #good_first_issue #faststream #zmqtt sent via relator