fml-syntax

Parser and formatter for the FHIR Mapping Language (FML), in Rust.

Lossless. The syntax tree keeps every byte of the input, comments and whitespace included: parse(text).syntax().to_string() == text for any input.
Error-tolerant. A mistake becomes a diagnostic and an error node; the rest of the file still parses, so one typo does not hide the next one. Positions are given in bytes, lines and UTF-16 columns.
A formatter that keeps comments. One statement per line, consistent spacing, comments where they were. It re-parses its own output and refuses to return text that would change the map.
The real-world grammar. The Mapping Language IG grammar, plus what maps written for FHIR R3–R5 use and the HL7 reference compiler accepts: map "url" = "name", unparenthesised where, embedded conceptmap with unmapped, <<type+>> groups.

All 1,659 public maps we test against parse without errors, and formatting each of them twice gives the same result as formatting it once.

let parse = fml_syntax::parse(source);
for diagnostic in parse.diagnostics() {
    eprintln!("{}", diagnostic.message);
}
for group in parse.tree().groups() {
    for rule in group.rules() {
        // sources, targets, transforms, dependent rules…
    }
}
let formatted = fml_syntax::format(source, &fml_syntax::FormatOptions::default())?;

Part of fml-rs. Licensed under MIT or Apache-2.0.

fml-syntax 0.2.0

fml-syntax