Enum ValueTypePersistence 

pub enum ValueTypePersistence {
    Persistable(AnyEncodeFn, AnyDecodeFn<SharedReference>),
    SkipPersist {
        expensive: bool,
    },
    HashOnly,
    SessionStateful,
}

Cell-persistence behavior of a ValueType.

Carries the serializer/deserializer pair for Persistable values — today that’s bincode, but the enum name is neutral so the choice of mechanism can evolve without a cascade of rename work.

Variants

Persistable(AnyEncodeFn, AnyDecodeFn<SharedReference>)

Cells are serialized to the persistent cache and restored on next access after eviction. Maps to serialization = "auto" | "custom".

SkipPersist

The value type opts out of being persisted: re-running the producing task to reproduce the cell is preferred over serializing the in-memory form. Cells are evictable; the next reader after eviction triggers a recompute from the task’s inputs. Maps to serialization = "skip" (plus an optional evict attribute).

Fields

expensive: bool

Whether re-deriving this cell is non-trivial (e.g. WASM compile, spawning a Node process pool). Eviction policy may prefer evicting cheap cells first. True iff declared with serialization = "skip", evict = "last".

HashOnly

The value type is not persisted, but the macro emitted a DeterministicHash derive and the write path stashes a content_hash into cell_data_hash so post-eviction reads can detect unchanged content and skip invalidation. Maps to serialization = "hash".

SessionStateful

Not persistable, not reconstructible — holds interior-mutable state that accumulates across the session (State<> cells, Arc<Mutex<_>> dedup histories). Re-running the producing task would lose the accumulated state, so cells of this type must stay in memory across eviction. Maps to serialization = "skip", evict = "never".