Replace Nested Conditional with Guard Clauses

Removes smells

Symptom

A function with deeply nested if/else where the happy path is buried under indentation; the agent must trace through edge-case branches to find the main flow.

Goal

Edge cases exit at the top of the function; the happy path runs at the function's base indent level, and adding a precondition is one new guard at the top instead of a rewrite of the nested branches.

Before the refactoring

function payAmount(employee) {
  if (employee.isSeparated) {
    return separationPay(employee);
  } else {
    if (employee.isRetired) {
      return retirementPay(employee);
    } else {
      return regularPay(employee);
    }
  }
}

After the refactoring

function payAmount(employee) {
  if (employee.isSeparated) return separationPay(employee);
  if (employee.isRetired)   return retirementPay(employee);
  return regularPay(employee);
}

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

Pressure

The agent's parsing of the function's intent is obscured by indentation; reasoning about the happy path requires tracking which edge cases have already been ruled out.

Tradeoff

Early returns can duplicate work if multiple paths share follow-up logic; the agent inlining guards must verify the shared work is genuinely separable.

Relief

Guards exit at the top of the function and the happy path runs at the function's base indent level; adding a precondition is one new guard prepended at the top instead of a rewrite of the nested branches.

Trap

Inlining guards for every condition — including ones that shared follow-up work — fragments the shared logic across early-return branches the agent must keep consistent.