Git exec(): child killed by a signal rejects with new Error('') and loses the signal information

[joewalker]

Observed behavior

The internal exec helper in src/util/git.ts resolves/rejects on the close event:

cmdProcess.on('close', (code: number): void => {
  if (code === 0) {
    resolve(outputs.join(''));
  } else {
    reject(new Error(outputs.join('')));
  }
});

Node's documentation says code may be null if the child was terminated by a signal (the signal name is the second argument to the listener). In that case:

1. The type annotation code: number is wrong (it can be null).
2. The rejection becomes new Error('') if the child was killed before producing any output, with no indication that it was killed or by which signal.

Expected behavior

The error should communicate either the non-zero exit code or the signal name, so a caller (or a developer reading logs) can tell why git terminated.

Minimal reproduction

import { spawn } from 'node:child_process';
const child = spawn('sleep', ['10']);
const outputs = [];
child.stdout?.on('data', d => outputs.push(String(d)));
child.stderr?.on('data', d => outputs.push(String(d)));
child.on('close', (code, signal) => {
  console.log('code=', code, 'signal=', signal);
  if (code === 0) { console.log('resolve', JSON.stringify(outputs.join(''))); }
  else { console.log('reject', JSON.stringify(outputs.join(''))); }
});
setTimeout(() => child.kill('SIGTERM'), 50);
// -> code= null signal= SIGTERM
// -> reject \"\"

Suggested fix

cmdProcess.on('close', (code: number | null, signal: NodeJS.Signals | null): void => {
  if (code === 0) {
    resolve(outputs.join(''));
    return;
  }
  const detail = outputs.join('');
  const reason = signal != null
    ? `git was killed by ${signal}`
    : `git exited with code ${code}`;
  reject(new Error(detail ? `${reason}: ${detail}` : reason));
});