disabling AutoReconnect causes spurious error to be logged

[rittneje]

We set AutoReconnect to false in our ClientOptions. When the connection to the broker is lost unexpectedly, we see the following error come from this library:

[client] BUG BUG BUG reconnection function is nil

Tracing through the code, this is because disDone is assigned like so.

paho.mqtt.golang/client.go

Line 517 in 714f7c0

disDone, err := c.status.ConnectionLost(c.options.AutoReconnect && c.status.ConnectionStatus() > connecting)

Since c.options.AutoReconnect is false, that will pass false to c.status.ConnectionLost. Thus the callback that it returns will itself return nil, nil.

paho.mqtt.golang/status.go

Lines 278 to 280 in 714f7c0

	if !reconnectRequested || !proceed {
	return nil, nil
	}

This in turn triggers the log that "should never happen".

paho.mqtt.golang/client.go

Lines 547 to 552 in 714f7c0

	reConnDone, err := disDone(true)
	if err != nil {
	ERROR.Println(CLI, "failure whilst reporting completion of disconnect", err)
	} else if reConnDone == nil { // Should never happen
	ERROR.Println(CLI, "BUG BUG BUG reconnection function is nil", err)
	}

I believe this regression was introduced in v1.4.2. It prevents us from upgrading from v1.3.5.

[stoxx]

I've assumed it's harmless.

[MattBrittan]

The library has quite a few options and I was concerned that I may have missed some possible combinations when rearchitecting the status handling (it was a bit of a mess), hence the "BUG BUG" log entry. Have had a quick look and the log entry should be supressed if c.options.AutoReconnect == false (probably best to add something like reconnectExpected := c.options.AutoReconnect && c.status.ConnectionStatus() > connecting at the top, and then use that value).
Having said that the code looks like it will work OK, it's just an incorrect log entry. Will fix when I get a chance (or would welcome a PR).