Enum PrepareOutcome 

#[non_exhaustive]
pub enum PrepareOutcome {
    NoOp,
    Applied {
        description: String,
    },
}

Outcome of an EngineBackend::prepare call — one-time backend-specific boot preparation.

Issue #281: moves cairn’s ensure_library retry loop upstream so consumers can boot any backend uniformly via backend.prepare().await? without knowing whether it is Valkey (FUNCTION LOAD) or Postgres (migrations are out-of-band per RFC-v0.7 Wave 0 Q12, so NoOp). #[non_exhaustive] so future backends can add variants (e.g. Skipped { reason }) additively.

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.

NoOp

Backend had nothing to do — either genuinely no-op (Postgres: migrations applied out-of-band) or the requested prep work was already in place and idempotent (Valkey: library already at the expected version; the Valkey impl collapses the “already-present” case into Applied to keep one success variant — consumers that want to distinguish can parse description).

Applied

Backend ran preparation work (e.g. Valkey FUNCTION LOAD REPLACE). description is a human-readable summary suitable for info!-level log lines like "FUNCTION LOAD (flowfabric lib v<N>)"; shape is not machine-parseable and MAY change across versions.

Fields

description: String

Human-readable summary of what was prepared.

Implementations

impl PrepareOutcome

pub fn applied(description: impl Into<String>) -> Self

Shorthand constructor for the Applied variant.

Trait Implementations

impl Clone for PrepareOutcome

fn clone(&self) -> PrepareOutcome

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for PrepareOutcome

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

Formats the value using the given formatter.

impl PartialEq for PrepareOutcome

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Eq for PrepareOutcome

impl StructuralPartialEq for PrepareOutcome