Some public Paho client properties and methods are not exposed - example username_pw_set()

[skewty]

Please either expose the Paho "Client" as a property (less preferred) or expose all its public methods and properties (preferred - also offers ability to place type hints).

Example of missing method is username_pw_set().

def username_pw_set(self, username: str | None = None, password: str | None) -> None:
    self._client.username_pw_set(username, password)

Otherwise accessing them must be done via protected "_client" which leads to linting warnings
unless something like this getattr(client, "_client").username_pw_set(username=token) is used.

[frederikaalund]

Hi Scott, thanks for opening this issue. Let me have a look. :)

This is a really good point. 👍 There are other issues around (as you've found; thanks for the PR!) about specific properties/methods already. It is clearly something that our users want. :)

We (asyncio-mqtt team) won't expose the underlying paho-mqtt client. Through the paho client, the user can, e.g., change the callbacks and break the higher-level API. It's a footgun.

Instead, we (asyncio-mqtt team) welcome PRs that expose properties/methods in an API-compatible way. 👍 It's actually a really good "first PR" since it's mostly just calling the underlying method on the paho-mqtt client.

Let me know if anything is unclear, or, if you have questions. 👍

~Frederik

[skewty]

Part of the difficulty with this is how the Paho client keeps many values protected. I spent some time yesterday looking into cleanest solution for many of the fields. In the end I came up with the following subclass of the Paho client with more fields exposed. Then the async Client class just instantiates this more exposed subclass.

class PahoClient(mqtt.Client):
    """Paho client with some exposed protected values"""

    @property
    def client_id(self) -> str:
        return self._client_id.decode()

    @client_id.setter
    def client_id(self, value: str) -> None:
        if value == "":
            if self._protocol == ProtocolVersion.V31:
                self._client_id = base62(uuid4().int, padding=22)  # copied from paho code
            else:
                self._client_id = b""
        else:
            self._client_id = value.encode()

    @property
    def host(self) -> str:
        return self._host

    @host.setter
    def host(self, value: str):
        self._host = str(value)

    @property
    def port(self) -> int:
        return self._port

    @port.setter
    def port(self, value: int) -> None:
        value = int(value)
        if 0x0000 <= value <= 0xFFFF:
            self._port = value
        raise ValueError("port number out of range")

    @property
    def username(self) -> str | None:
        return None if self._username is None else self._username.decode()

    @username.setter
    def username(self, value: str | None):
        self._username = None if value is None else value.encode()

    @property
    def password(self) -> str | None:
        return None if self._password is None else self._password.decode()

    @password.setter
    def password(self, value: str | None):
        self._password = None if value is None else value.encode()

    @property
    def connect_timeout(self) -> float:
        return self._connect_timeout

    @connect_timeout.setter
    def connect_timeout(self, value: float) -> None:
        value = float(value)
        if value <= 0.0:
            raise ValueError("timeout must be a positive number")
        self._connect_timeout = value

    @property
    def keep_alive(self) -> int:
        return self._keepalive

    @keep_alive.setter
    def keep_alive(self, value: int) -> None:
        value = int(value)
        if value <= 0:
            raise ValueError("keepalive must be a positive number")
        self._keepalive = value

    @property
    def max_inflight_messages(self) -> int:
        return self._max_inflight_messages

    @max_inflight_messages.setter
    def max_inflight_messages(self, value: int) -> None:
        if value < 0:
            raise ValueError("value must not be negative")
        self._max_inflight_messages = value

    @property
    def max_queued_messages(self) -> int:
        return self._max_queued_messages

    @max_queued_messages.setter
    def max_queued_messages(self, value: int) -> None:
        if value < 0:
            raise ValueError("value must not be negative")
        self._max_queued_messages = value

    @property
    def will_topic(self) -> str:
        return self._will_topic.decode()

    @property
    def will_payload(self) -> bytes:
        return self._will_payload

Your thoughts on an approach like this?

[frederikaalund]

Thanks for taking your time to look into this issue. 👍

Your thoughts on an approach like this?

In short: I fear the maintenance burden if we start to rely on private/protected member variables/methods. :)

paho-mqtt chose not to expose these variables/methods. There may or may not be a good reason for this. In any case, I vote that we don't depend on the non-public part of the paho-mqtt library.

As a side note, I know that we already do this for _client_id. That was a mistake on my part. I'd rather get rid of that than go further down that road. 😅

---

Alternative 1

Expose all the keyword-only parameters of Client.__init__. Basically make a bunch of propertys so that the user gets read-only access. That doesn't cover all the underlying API surface but it's a start.

Alternative 2

Move this issue to paho-mqtt first. That is, first convince paho-mqtt to expose these member variables in their public API (basically copy-paste of your property declarations 👍). Then, we can forward the very same properties in asyncio-mqtt as well.

---

Personally, I lean towards Alternative 2. What do you think?

I hope that makes sense. :) Again, thanks for looking into this!

[skewty]

Also: eclipse-paho/paho.mqtt.python#765

[skewty]

I tried Alternative 2 and didn't get anywhere. Closing for now.