const fs = require('fs');
const { SourceMapConsumer } = require('source-map');
(async () => {
  const mapJson = await (await fetch('http://127.0.0.1:8099/main.dart.js.map')).text().catch(()=>null);
  if (!mapJson) { console.log('无 sourcemap'); return; }
  const smc = await new SourceMapConsumer(mapJson);
  // 解析 299:254 (line:col)
  const pos = smc.originalPositionFor({ line: 299, column: 254 });
  console.log('299:254 →', pos.source, pos.line + ':' + pos.column, '|', pos.name);
  // 也试 299 的前后几行
  for (const c of [200, 100, 50]) {
    const p = smc.originalPositionFor({ line: 299, column: c });
    if (p.source) console.log(`299:${c} →`, p.source.split('/').slice(-2).join('/') + ':' + p.line);
  }
})();