Struct PendingPublish 

pub struct PendingPublish {
    pub progress_tx: Sender<PublishProgress>,
    pub completion_tx: Sender<Result<ReasonCode, Error>>,
    pub deadline: Option<Instant>,
}

Held by the event loop for each in-flight QoS >= 1 publish.

Tracking is keyed by PacketId, which per §4.4 is preserved across reconnects when the session is resumed and so doubles as the stable handle for the user-facing completion future.

Fields

progress_tx: Sender<PublishProgress>

Kept alive so the watch channel doesn’t error on recv while the caller is still observing progress.

completion_tx: Sender<Result<ReasonCode, Error>>

deadline: Option<Instant>

Ack-timeout deadline, set once the packet is written to the wire and only when ack_timeout is enabled. Mirrors the entry in Pending deadline schedule so the schedule entry can be removed on acknowledgement.