MQTTDefaultSubscriber

@override
async def start(self) -> None:
    # Re-resolve the parser now that _outer_config is fully composed
    # (i.e. include_router has been called and the broker's MQTTBrokerConfig
    # is reachable through the config chain).
    parser = self._build_parser()
    self._parser = parser.parse_message
    self._decoder = parser.decode_message

    await super().start()

    if self.calls:
        await self._create_subscription()
        self.add_task(self._consume_loop, restart_on_failure=False)

    self._post_start()

@override
async def stop(self) -> None:
    # Stop receiving before TasksMixin cancels the consume task. In particular,
    # StopConsume calls this method from that task, so cancelling it first would
    # also cancel an in-flight UNSUBSCRIBE.
    self.running = False
    if self._subscription is not None:
        with suppress(Exception):
            await self._subscription.stop()
        self._subscription = None

    await super().stop()

def add_call(
    self,
    *,
    parser_: Optional["CustomCallable"],
    decoder_: Optional["CustomCallable"],
    dependencies_: Sequence["Dependant"],
    codec_: Optional["CodecProto"] = None,
) -> Self:
    self._call_options = _CallOptions(
        parser=parser_,
        decoder=decoder_,
        dependencies=dependencies_,
        codec=codec_,
    )
    return self

async def consume(self, msg: MsgType) -> Any:
    """Consume a message asynchronously."""
    if not self.running:
        return None

    try:
        return await self.process_message(msg)

    except StopConsume:
        # Stop handler at StopConsume exception
        await self.stop()

    except SystemExit:
        # Stop handler at `exit()` call
        await self.stop()

        if app := self._outer_config.context.get("app"):
            app.exit()

    except Exception:  # nosec B110  # noqa: S110
        # All other exceptions were logged by CriticalLogMiddleware
        pass

async def process_message(self, msg: MsgType) -> "Response":
    """Execute all message processing stages."""
    context = self._outer_config.context
    logger_state = self._outer_config.logger

    async with AsyncExitStack() as stack:
        stack.enter_context(self.lock)

        # Enter context before middlewares
        stack.enter_context(
            context.scopes(
                (
                    ("handler_", self),
                    ("logger", logger_state.logger.logger),
                    *self._outer_config.extra_context.items(),
                ),
            ),
        )

        # enter all middlewares
        middlewares: list[BaseMiddleware] = []
        for base_m in self.__build__middlewares_stack():
            middleware = base_m(msg, context=context)
            middlewares.append(middleware)
            await middleware.__aenter__()

        cache: dict[Any, Any] = {}
        parsing_error: Exception | None = None
        for h in self.calls:
            try:
                message = await h.is_suitable(msg, cache)
            except Exception as e:
                parsing_error = e
                break

            if message is not None:
                stack.enter_context(
                    context.scopes(
                        (
                            ("log_context", self.get_log_context(message)),
                            ("message", message),
                        ),
                    ),
                )

                # Middlewares should be exited before scope release
                for m in middlewares:
                    stack.push_async_exit(m.__aexit__)

                result_msg = ensure_response(
                    await h.call(
                        message=message,
                        # consumer middlewares
                        _extra_middlewares=(
                            m.consume_scope for m in middlewares[::-1]
                        ),
                    ),
                )

                if not result_msg.correlation_id:
                    result_msg.correlation_id = message.correlation_id

                for p in chain(
                    self.__get_response_publisher(message),
                    h.handler._publishers,
                ):
                    await p._publish(
                        result_msg.as_publish_command(),
                        _extra_middlewares=(
                            m.publish_scope for m in middlewares[::-1]
                        ),
                    )

                # Return data for tests
                return result_msg

        # Suitable handler was not found or
        # parsing/decoding exception occurred
        for m in middlewares:
            stack.push_async_exit(m.__aexit__)

        # Reraise it to catch in tests
        if parsing_error:
            raise parsing_error

        error_msg = f"There is no suitable handler for {msg=}"
        raise SubscriberNotFound(error_msg)

    # An error was raised and processed by some middleware
    return ensure_response(None)

@override
async def get_one(
    self,
    *,
    timeout: float = 5.0,
) -> "MQTTMessage | None":
    assert not self.calls, (
        "You can't use `get_one` method if subscriber has registered handlers."
    )

    if self._subscription is None:
        auto_ack = self.ack_policy is AckPolicy.ACK_FIRST
        self._subscription = self._outer_config.client.subscribe(
            self.topic,
            qos=zmqtt.QoS(self._qos),
            auto_ack=auto_ack,
        )
        await self._subscription.start()

    async_parser, async_decoder = self._get_parser_and_decoder()

    raw_msg: zmqtt.Message | None = None
    with anyio.move_on_after(timeout):
        raw_msg = await self._subscription.get_message()

    context = self._outer_config.context
    msg: MQTTMessage | None = await process_msg(  # type: ignore[assignment]
        msg=raw_msg,
        middlewares=(m(raw_msg, context=context) for m in self._broker_middlewares),
        parser=async_parser,
        decoder=async_decoder,
    )
    return msg

def get_log_context(
    self,
    message: "StreamMessage[zmqtt.Message] | None",
) -> dict[str, str]:
    return self.build_log_context(message=message, topic=self.topic)

def schema(self) -> dict[str, "SubscriberSpec"]:
    self._build_fastdepends_model()
    return self.specification.get_schema()

def add_task(
    self,
    func: Callable[..., Coroutine[Any, Any, Any]],
    func_args: tuple[Any, ...] | None = None,
    func_kwargs: dict[str, Any] | None = None,
    *,
    restart_on_failure: bool = True,
) -> None:
    args = func_args or ()
    kwargs = func_kwargs or {}
    task = asyncio.create_task(func(*args, **kwargs))
    callback = TaskCallbackSupervisor(
        func,
        func_args,
        func_kwargs,
        self,
        restart_on_failure=restart_on_failure,
    )
    task.add_done_callback(callback)
    self.tasks.append(task)

@staticmethod
def build_log_context(
    message: "StreamMessage[zmqtt.Message] | None",
    topic: str = "",
) -> dict[str, str]:
    return {
        "topic": topic,
        "message_id": getattr(message, "message_id", ""),
    }