Function eval_key 

pub fn eval_key(
    config: &RepoConfig,
    eval: &Eval,
    fingerprints: &BTreeMap<&ArtifactName, PreparedFingerprint>,
) -> Result<Key, Unkeyed>

The eval’s reuse key from prepared fingerprints. Without a fingerprint on every Artifact it depends on, the eval has no key, so it is never reused or published.