Function evaluate_cache 

pub fn evaluate_cache(
    venv_path: &Path,
    metadata_path: &Path,
    expected_requirements_hash: &str,
    expected_manifest_version: Option<&str>,
    expected_manifest_hash: Option<&str>,
) -> CacheVerdict

Decide whether a cached venv can be reused.

expected_manifest_version and expected_manifest_hash are what the plugin declares now; the metadata carries what was true at install time. A metadata signal that is absent is skipped rather than compared — see the module docs for why that asymmetry matters.