Enum SubscribeError 

pub enum SubscribeError {
    EmptyWakeKeys,
}

Why a set of wake keys could not be accepted.

Variants

EmptyWakeKeys

A runtime-built collection of wake keys turned out to be empty.

Matching is set overlap, so an empty set intersects nothing: no event could ever reach such a subscription through the waker, and the first time it passivated it would stay Dormant forever with its events unread.

WakeKeys makes that unrepresentable, so this is reachable only through WakeKeys::try_from — the one place a type cannot decide, because the keys came from data rather than from the call site. It is deliberately raised there rather than inside Subscriptions::subscribe_in_op, so the caller handles it where the domain context to interpret an empty set actually exists.

A subscriber that genuinely wants waking on every event says so explicitly: declare one constant key and return that key from SubscriptionDef::wake_keys for every event. That costs a wake per event by construction, which is the point — the price is visible in the caller’s own code instead of hidden in an empty vector.

Trait Implementations

impl Debug for SubscribeError

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

Formats the value using the given formatter.

impl Display for SubscribeError

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

Formats the value using the given formatter.

impl Error for SubscribeError

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.