mqtt.client:connect() "not established" callback is unexpectedly called after a disconnect - lua

Question

The documentation for mqtt.client:connect() states that the last arg is a "callback function for when the connection could not be established".
I have a case where mqtt.client:connect() succeeds, so the "not established" callback is not called (correct behavior). But, later, when my mqtt broker goes down, the "not established" callback function gets unexpectedly activated.
I have the following code:
function handle_mqtt_error (client, reason)
print("mqtt connect failed, reason = "..reason..". Trying again shortly.")
tmr.create():alarm(10 * 1000, tmr.ALARM_SINGLE, do_mqtt_connect)
end
function do_mqtt_connect ()
print("connecting---")
m:connect(MQTT_HOST, MQTT_PORT, 1, function(client)
print("mqtt connected")
client:publish("topic/status", "online", 1, 1)
end,
handle_mqtt_error
)
print("returning---")
end
-- init mqtt client
m = mqtt.Client(MQTT_CLIENT_ID, 120, MQTT_USER, MQTT_PASS)
-- connect to mqtt
print("Starting Test")
do_mqtt_connect()
I see the output from the test begin, as expected, with:
Starting Test
connecting---
returning---
mqtt connected
At this point, I kill my mqtt broker, and I unexpectedly see:
mqtt connect failed, reason = -5. Trying again shortly.
connecting---
returning---
mqtt connect failed, reason = -5. Trying again shortly.
connecting---
returning---
And, happily, but unexpectedly, when I restart my broker, I see:
mqtt connected
So, it appears that handle_mqtt_error() is not only called "when the connection could not be established". It appears that it also be called if mqtt.client:connect() successfully establishes a connection, then the connection is later broken.
======= New Information =======
I downloaded the "dev" tree and used the Docker image to build the firmware. Within mqtt.c, I enabled NODE_DBG. The interesting lines are:
enter mqtt_socket_reconnected.
mqtt connect failed, reason = -5. Trying again shortly.
enter mqtt_socket_disconnected.
leave mqtt_socket_disconnected.
leave mqtt_socket_reconnected.
The "mqtt connect failed..." message is printed by handle_mqtt_error(), which is my "connect failed" callback.
Here's my theory. When my test starts, do_mqtt_connect() calls mqtt_socket_connect(), which does this:
espconn_regist_reconcb(pesp_conn, mqtt_socket_reconnected);
This sets reconnect_callback (in app/lwip/app/espconn.c). Later, after my broker goes down and comes back up, espconn_tcp_reconnect() is called (in app/lwip/app/espconn_tcp.c). It calls the reconnect_callback, which is mqtt_socket_reconnected(), which calls handle_mqtt_error().
So, I think the end result doesn't match the documentation, but it works out okay for me. If the behavior did match the documentation, I would just add some Lua code to handle the "offline" event, and try to reestablish the mqtt connection. I just thought someone might be interested if the behavior doesn't match the documentation.