fn parse_rustc_cfg_output()

in cargo/cargo_build_script_runner/bin.rs [246:272]

• 22 lines of code
• 8 McCabe index (conditional complexity)

fn parse_rustc_cfg_output(stdout: &str) -> BTreeMap<String, String> {
    let mut values = BTreeMap::new();

    for line in stdout.lines() {
        if line.starts_with("target_") && line.contains('=') {
            let mut parts = line.splitn(2, '=');
            // UNWRAP: Verified that line contains = and split into exactly 2 parts.
            let key = parts.next().unwrap();
            let value = parts.next().unwrap();
            if value.starts_with('"') && value.ends_with('"') && value.len() >= 2 {
                values
                    .entry(key)
                    .or_insert_with(Vec::new)
                    .push(value[1..(value.len() - 1)].to_owned());
            }
        } else if ["windows", "unix"].contains(&line) {
            // the 'windows' or 'unix' line received from rustc will be turned
            // into eg. CARGO_CFG_WINDOWS='' below
            values.insert(line, vec![]);
        }
    }

    values
        .into_iter()
        .map(|(key, value)| (format!("CARGO_CFG_{}", key.to_uppercase()), value.join(",")))
        .collect()
}