no-swallowed-errors.md

llm-core/no-swallowed-errors

📝 Disallow catch blocks that only log to console and swallow the error.

💼 This rule is enabled in the following configs: 🌐 all, 🏆 best-practices, ✅ recommended.

Disallow catch blocks that only call console.log, console.warn, console.error, or console.debug without rethrowing, returning, or delegating the failure to a real error handler.

Rule Details

LLMs often generate placeholder error handling like catch (error) { console.error(error); }. That looks intentional, but it still swallows the failure: callers do not see an error, control flow continues, and production systems quietly drift into bad state.

This rule focuses on the narrow, high-signal case where a non-empty catch block contains only console logging calls. It deliberately does not overlap with no-empty-catch — truly empty or comment-only blocks belong to that rule.

Examples

Incorrect

try {
  await processOrder(order);
} catch (error) {
  console.error(error);
}

try {
  await loadConfig();
} catch (error) {
  console.warn("Config failed", error);
  console.debug(error);
}

Correct

try {
  await processOrder(order);
} catch (error) {
  throw new Error("Failed to process order", { cause: error });
}

try {
  return await loadConfig();
} catch (error) {
  logger.error("Config load failed", { error });
  return null;
}

try {
  await publishEvent(event);
} catch (error) {
  Sentry.captureException(error);
}

try {
  await performWork();
} catch (error) {
  console.error(error);
  throw error;
}

What This Rule Flags

Catch body contents	Flagged?
console.error(error)	✅ Yes
console.log(error); console.warn("failed", e)	✅ Yes
console.error(error); throw error;	❌ No
console.error(error); handleError(error);	❌ No
handleError(error)	❌ No
empty catch {}	❌ No

Why Console-Only Handling Is Risky

• Logging alone does not change control flow.
• Callers cannot recover because they never learn the operation failed.
• Background tasks can keep running with partial or invalid state.
• The code looks "handled" in review even though the failure was dropped.

Error Messages

The teaching message explains:

1. What's wrong — the catch block only logs and swallows the error
2. Why — execution continues as if nothing failed
3. How to fix — rethrow, return an explicit fallback, or delegate to a real handler such as a logger or error tracker