Replace Exception with Precheck

Removes smells

Symptom

The agent finds try/catch for conditions the caller could check directly; control flow via exceptions obscures the rule.

Goal

The precheck appears at the point of decision; the agent reads the code top-to-bottom as the rule, with exceptions reserved for truly exceptional cases.

Before the refactoring

try {
  return amounts[i] / 100;
} catch (e) {
  return 0;
}

After the refactoring

if (i >= amounts.length) return 0;
return amounts[i] / 100;

Example source: Illustrative example written for this site, not a quotation from any source.

Pressure

The agent debugging exception flow must reason about catch handlers; benign throws fire breakpoints; the rule that 'should fire' isn't obvious from reading.

Tradeoff

Race conditions: the precheck may pass and the operation still fail (TOCTOU); the agent using prechecks must verify the caller can check the condition atomically.

Relief

The agent reads the rule top-to-bottom; debuggers stop catching benign throws; exception handlers reserve for truly exceptional cases.

Trap

Replacing exceptions with prechecks for conditions the caller can't atomically verify introduces race windows the agent's local tests won't catch.