Client does not resubscribe after reconnect if clean = false

[holopekochan]

Is there any reason we don't want resubscribe work if clean = false?
I have created a sub client with clean = false, and resubscribe = true, the client will not resubscribe the topics if MQTT aedes broker (no persistence) restart. And, sub-client will no longer receive the message of the topics
https://github.com/mcollina/aedes

https://github.com/mqttjs/MQTT.js/blob/master/lib/client.js
From MQTT.js/lib/client.js

 MqttClient.prototype._resubscribe = function () {
  if (!this._firstConnection &&
      this.options.clean &&
      Object.keys(this._resubscribeTopics).length > 0) {
    if (this.options.resubscribe) {
      this._resubscribeTopics.resubscribe = true
      this.subscribe(this._resubscribeTopics)
    } else {
      this._resubscribeTopics = {}
    }
  }

I can provide my sub client code and broker code if necessary

[zz123er]

@#749

[VirtualWolf]

I just ran into this myself with MQTT.js 4.2.8 and using Mosquitto 2.0.12 as the broker, and was extremely surprised by the behaviour. Was there a specific reason for it behaving like this, or is it some unintended bug?

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[Hypfer]

bump

[simonnilsson]

The sessionPresentFlag should be available since version 3.1.1. And it is possible for broker to lose the persistent session, in that case you would want the client to automatically resubscribe.

Thus this line:

MQTT.js/src/lib/client.ts

Lines 2108 to 2110 in 18bdd49

	(this.options.clean ||
	(this.options.protocolVersion === 5 &&
	!this.connackPacket.sessionPresent)) &&

Should be:

(this.options.clean || (this.options.protocolVersion >= 4 && !this.connackPacket.sessionPresent)) &&

Right?
@robertsLando

This problem seem to be observed in multiple issues
#749, #895, #1288

I can make a pull request for this. Not sure if this would be considered a breaking change, But I think most people woud expect resubscribe to work like this.

[robertsLando]

Yeah that's a bug. Open a PR if possible, remember to add a test. Thanks