Function runForwarded

packages/container/src/dev.ts:113–170

* Run a command to completion, forwarding its stdout/stderr to the dev output * sink so it gets the per-service log prefix. Resolves stdout for parsing.

(
  cmd: string,
  args: string[],
  out: DevOutput,
  opts: { quiet?: boolean } = {}
)

 * sink so it gets the per-service log prefix. Resolves stdout for parsing.
 */
function runForwarded(
  cmd: string,
  args: string[],
  out: DevOutput,
  opts: { quiet?: boolean } = {}
): Promise<{ stdout: string }> {
  return new Promise((resolve, reject) => {
    const child = spawn(cmd, args, { stdio: ['ignore', 'pipe', 'pipe'] });
    let stdout = '';
    let stderr = '';
    child.stdout?.on('data', (chunk: Buffer) => {
      stdout += chunk.toString();
      if (!opts.quiet) {
        if (out.onStdout) {
          out.onStdout(chunk);
        } else {
          process.stderr.write(chunk.toString());
        }
      }
    });
    child.stderr?.on('data', (chunk: Buffer) => {
      stderr += chunk.toString();
      if (!opts.quiet) {
        if (out.onStderr) {
          out.onStderr(chunk);
        } else {
          process.stderr.write(chunk.toString());
        }
      }
    });
    child.on('error', (err: NodeJS.ErrnoException) => {
      if (err.code === 'ENOENT') {
        reject(
          new Error(
            `Command not found: \`${cmd}\`. Ensure \`${cmd}\` is installed ` +
              'and on your PATH (Docker is required for `vercel dev` with ' +
              'container services).'
          )
        );
        return;
      }
      reject(err);
    });
    child.on('close', code => {
      if (code === 0) {
        resolve({ stdout });
      } else {
        const detail = stderr.trim().split('\n').slice(-5).join('\n');
        reject(
          new Error(
            `\`${cmd} ${args.join(' ')}\` exited with code ${code}` +
              (detail ? `\n${detail}` : '')
          )
        );
      }
    });
  });
}