Function startMetroProcess

src/metro/client-metro.ts:373–402

(
  projectRoot: string,
  kind: ResolvedMetroKind,
  port: number,
  listenHost: string,
  logPath: string,
  env: EnvSource,
)

}

function startMetroProcess(
  projectRoot: string,
  kind: ResolvedMetroKind,
  port: number,
  listenHost: string,
  logPath: string,
  env: EnvSource,
): MetroProcessResult {
  const metro = buildMetroCommand(kind, port, listenHost);
  fs.mkdirSync(path.dirname(logPath), { recursive: true });
  const logFd = fs.openSync(logPath, 'a');
  let pid = 0;
  try {
    pid = runCmdDetached(metro.command, metro.installArgs, {
      cwd: projectRoot,
      env: env as NodeJS.ProcessEnv,
      stdio: ['ignore', logFd, logFd],
    });
  } finally {
    fs.closeSync(logFd);
  }

  if (!Number.isInteger(pid) || pid <= 0) {
    throw new Error('Failed to start Metro. Expected a detached child PID.');
  }

  return {
    pid,
  };
}

async function stopSpawnedMetroProcess(pid: number): Promise<void> {
  if (!Number.isInteger(pid) || pid <= 0) return;