Function try_format_marker 

pub fn try_format_marker(
    prefix: &str,
    label: &str,
    counters: BenchmarkCounters,
) -> Result<String, BenchmarkMarkerError>

Format one complete marker after admitting its prefix and start/end label.

Printable Unicode and spaces remain literal. No fields are escaped or trimmed. The parser must separately be configured to accept this prefix.

Errors

Refuses empty prefixes, pipe/CR/LF delimiters and labels without a nonempty span followed by :start or :end. Errors do not include the rejected text.