Enum FetchPolicy 

pub enum FetchPolicy {
    CacheFirst,
    Refresh,
    AcceptUpstreamChange,
}

How a fetch treats an existing cache hit (D-02, D-09). All three behave IDENTICALLY on a cache MISS — the miss path (resolve, download, verify, persist) is implemented exactly once and is reached by every policy alike.

On a cache HIT, a re-released version upstream is refused BY DEFAULT: if the digest the feed publishes today differs from what’s cached for this version, the fetch refuses naming both digests and leaves the cached artifact usable and untouched. AcceptUpstreamChange is the deliberate, explicit way to accept that change — it downloads the new bytes and verifies them against the NEWLY published digest before caching them ALONGSIDE (never over) the old entry. Phase 16 wires these to a CLI flag.

Variants

CacheFirst

Trust an existing cache hit outright — never re-contact the feed for a version already cached. The default.

Refresh

Re-verify a cache hit against the feed’s current digest before trusting it: an unchanged digest reuses the cache (no re-download); a changed digest is REFUSED (module_digest_changed, exit 6), naming both digests, with the cached artifact left exactly as it was (15-02).

AcceptUpstreamChange

Accept a digest change the feed now reports for an already-cached version: downloads the new bytes and verifies them against the NEWLY published digest — never trusts them unverified — then persists them alongside (not over) the existing cache entry (15-02, D-02’s explicit override).

Trait Implementations

impl Clone for FetchPolicy

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for FetchPolicy

impl Debug for FetchPolicy

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

Formats the value using the given formatter.

impl Default for FetchPolicy

fn default() -> Self

Returns the “default value” for a type.

impl Eq for FetchPolicy

impl PartialEq for FetchPolicy

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for FetchPolicy