Function derive_child 

pub fn derive_child(
    root: &LocalAbsolutePath,
    name: &str,
) -> Result<LocalAbsolutePath, RunnerRootError>

The path of one attempt directory or persistent slot below root.

Containment is by construction: name must be a single component, so <root>/<12-char-attempt> and <root>/sN cannot escape however the caller spells them. That is the lexical half of the requirement; the canonical half is verify_containment, which is what a junction planted inside the root has to get past.

Errors

RunnerRootError::DerivedName when name is not one component, or is not a name this platform can store.