Module frontmatter 

Frontmatter mode: address the leading TOML (+++) or YAML (---) metadata block of a Markdown-ish file as a config document, leaving the body bytes untouched.

This backend does not parse Markdown. It splits the source into three byte-exact spans — the opening delimiter line, the frontmatter block, and the closing delimiter line plus everything after it (the body) — and hands only the middle span to the inner TOML/YAML backend. Every edit re-splices pre + edited_frontmatter + post, so the body survives verbatim; the frozen body is exactly why frontmatter mode is source-preserving-only (there is no whole-document re-render — the body is not part of the parsed value).

Detection is never automatic: the caller selects the delimiter explicitly (--input-format toml-frontmatter|yaml-frontmatter). A file that does not open with the requested delimiter, or whose block is never closed, is a hard error — sniffing a fence is exactly the shape-guessing AFDATA avoids.

Structs

Parts

Three byte-exact spans of a frontmatter document: the opening delimiter line (pre), the frontmatter block handed to the inner backend (frontmatter), and the closing delimiter line plus the body (post). Concatenating pre, frontmatter, and post reproduces the original source byte for byte.

Enums

Delimiter

The fence delimiter that brackets a frontmatter block.

Functions

split

Split source into its frontmatter spans for the given delimiter.