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decode_front_matter

dms

Function decode_front_matter 

Source 
pub fn decode_front_matter(src: &str) -> Result<Option<Value>, DecodeError>
Expand description

Front-matter-only decode. Scans leading trivia, the opening +++, the front-matter contents, and the closing +++, then stops — body bytes are NOT tokenized. Required at SPEC tier 0; see SPEC §“Front-matter-only decode” for the full contract.

Return value:

  • Ok(None) — the document has no front matter at all (no opening +++ after leading trivia).
  • Ok(Some(Value::Table(map))) — front matter was present. map is empty when the source carried +++\n+++\n with no inner keys, so callers can distinguish “no front matter” from “present-but-empty”.
  • Err(DecodeError) — every front-matter rule still applies: open/close on their own lines, unterminated front matter is an error, the _-prefix namespace is enforced (_dms_tier is type-checked, unknown reserved keys rejected). Diagnostics inside the +++ ... +++ block are byte-identical to a full decode.

Errors that only manifest in the body (duplicate body keys, unterminated body heredoc, …) are NOT surfaced — that’s the entire point of this entry point. Callers needing whole-document validation must use decode_document.

Runs in lite mode (no comment AST, no original_forms).