Function resolve_path 

pub fn resolve_path(
    root: &Value,
    path: &str,
    addressing: Addressing<'_>,
) -> DocumentResult<String>

Rewrite path into the equivalent index-only address for root.

Content addressing is something only the parsed value can answer, and the source-preserving writers never see it: each backend re-walks the original text by path, and nothing in identities.me tells a TOML editor which element me is. So a write resolves the address once, here, where the whole document is in hand, and hands the backends the canonical identities.0. The alternative — teaching six backends to match on content — would give each its own chance to disagree with the read walk about what an address means.

Resolution stops at the first segment the document does not have and copies the rest verbatim, because set creates missing object parents and a node that does not exist yet cannot be addressed by its content anyway. Whatever is wrong with the tail is then the writer’s error to report, unchanged.

Two prefixes are tracked because they answer different questions: the semantic one (the caller’s own segments) is what a KeyedList registration is matched against, so a registration keeps meaning what it meant on the read path, while the canonical one (resolved indices) is what gets returned.