Enum RequestError 

#[non_exhaustive]
pub enum RequestError<DE> {
    Timeout {
        elapsed: Duration,
    },
    Client(MqttClientError),
    Decode(DE),
    CallerClosed,
}

Failure of one RPC call, as seen by the requester.

This is the RPC machinery failing (timeout, transport, undecodable reply, caller shut down) — distinct from the remote application saying “no”, which a responder models in the payload via response = Result<Reply, MyError> (see docs/DESIGN_RPC.md §6).

DE is the serializer’s DeserializeError for the declared response type, mirroring DecodeFailure on the subscribe side.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Timeout

No reply arrived within the deadline. The request is NOT retracted (MQTT has no unsend), so the responder may still have executed the handler.

Fields

elapsed: Duration

How long the call waited before giving up.

Client(MqttClientError)

Publish/subscribe/transport failure. Carries RequiresV5 (via MqttClientError::Capability) when the connection is not MQTT 5.

Decode(DE)

The reply arrived but its payload failed to deserialize as the declared response type.

CallerClosed

The MqttRpcCaller (or the connection) shut down while this call was still awaiting its reply.

Implementations

impl RequestError<Infallible>

pub fn widen<DE>(self) -> RequestError<DE>

Widen the decode-error type of a reply-wait outcome.

The caller machinery (PendingReply::await_reply) can only produce Timeout / Client / CallerClosed — it never decodes, so its DE is Infallible. The macro-generated call body then decodes with the topic’s serializer and needs the concrete DE; this maps the payload-agnostic error across without a fallible cast (the Decode(Infallible) arm is unreachable).

Trait Implementations

impl<DE> Debug for RequestError<DE>

where DE: Debug,

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl<DE> Display for RequestError<DE>

where DE: Debug,

fn fmt(&self, __formatter: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl<DE> Error for RequestError<DE>

where RequestError<DE>: Debug + Display,

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.

impl<DE> From<MqttClientError> for RequestError<DE>

fn from(source: MqttClientError) -> RequestError<DE>

Converts to this type from the input type.