Enum TaskPresence 

#[non_exhaustive]
pub enum TaskPresence {
    Present {
        owner: TaskOwner,
    },
    Expired {
        owner: TaskOwner,
    },
    Missing,
}

Whether a task is present, expired, or was never known.

Option collapses the last two, so an application retaining expired tombstones cannot tell a caller “that task expired” rather than “no such task” (#1249).

The owner is carried for a reason

Expired keeps the owner because authorization has to happen before the distinction is revealed. A present or expired task belonging to another principal must remain indistinguishable from Missing to that caller, or tasks/get becomes an existence oracle: anyone could probe ids and learn which ones belong to somebody. Only the matching owner sees Expired.

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.

Present

The task exists and has not expired.

Fields

owner: TaskOwner

Principal that created it.

Expired

The task existed and its TTL elapsed.

Only reported by a store that retains expired records. One that drops them answers Missing, which is correct for it.

Fields

owner: TaskOwner

Principal that created it, needed to authorize before disclosing.

Missing

No such task, or the store no longer retains it.

Implementations

impl TaskPresence

pub fn owner(&self) -> Option<&TaskOwner>

The owner, for a task the store still knows about.

pub fn is_known(&self) -> bool

Whether the store knows this task at all, expired or not.

Trait Implementations

impl Clone for TaskPresence

fn clone(&self) -> TaskPresence

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for TaskPresence

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

Formats the value using the given formatter.

impl Eq for TaskPresence

impl PartialEq for TaskPresence

fn eq(&self, other: &TaskPresence) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for TaskPresence