reportMetric function
Emits one machine-readable benchmark sample on stdout.
Format: HINTFUL_BENCH_JSON:<json>. Every sample carries metric and a
nullable value (null = could not measure — the collector skips such
samples).
Implementation
void reportMetric(String metric, num? value, {Map<String, Object>? extra}) {
final payload = <String, Object?>{
'metric': metric,
'value': value,
if (extra != null) ...extra,
};
// ignore: avoid_print
print('$envelope${jsonEncode(payload)}');
}