General Clean Code Principles

Critical Rules

G5: DRY (Don't Repeat Yourself)

Every piece of knowledge has one authoritative representation.

// Bad - duplication
const taxRate = 0.0825;
const caTotal = subtotal * 1.0825;
const nyTotal = subtotal * 1.07;

// Good - single source of truth
const TAX_RATES: Record<string, number> = { CA: 0.0825, NY: 0.07 };
function calculateTotal(subtotal: number, state: string): number {
  return subtotal * (1 + TAX_RATES[state]);
}

G16: No Obscured Intent

Don't be clever. Be clear.

// Bad - what does this do?
return ((x & 0x0f) << 4) | (y & 0x0f);

// Good - obvious intent
return packCoordinates(x, y);

G23: Prefer Polymorphism to If/Else

// Bad - will grow forever
function calculatePay(employee: {
  type: "SALARIED" | "HOURLY" | "COMMISSIONED";
  salary?: number;
  hours?: number;
  rate?: number;
  base?: number;
  commission?: number;
}): number {
  if (employee.type === "SALARIED") {
    return employee.salary ?? 0;
  } else if (employee.type === "HOURLY") {
    return (employee.hours ?? 0) * (employee.rate ?? 0);
  } else if (employee.type === "COMMISSIONED") {
    return (employee.base ?? 0) + (employee.commission ?? 0);
  }
  return 0;
}

// Good - open/closed principle
interface Employee {
  calculatePay(): number;
}

class SalariedEmployee implements Employee {
  constructor(private readonly salary: number) {}
  calculatePay(): number {
    return this.salary;
  }
}

class HourlyEmployee implements Employee {
  constructor(
    private readonly hours: number,
    private readonly rate: number,
  ) {}
  calculatePay(): number {
    return this.hours * this.rate;
  }
}

class CommissionedEmployee implements Employee {
  constructor(
    private readonly base: number,
    private readonly commission: number,
  ) {}
  calculatePay(): number {
    return this.base + this.commission;
  }
}

G25: Replace Magic Numbers with Named Constants

// Bad
if (elapsedTime > 86400) {
  // ...
}

// Good
const SECONDS_PER_DAY = 86400;
if (elapsedTime > SECONDS_PER_DAY) {
  // ...
}

G30: Functions Should Do One Thing

If you can extract another function, your function does more than one thing.

G36: Law of Demeter (Avoid Train Wrecks)

// Bad - reaching through multiple objects
const outputDir = context.options.scratchDir.absolutePath;

// Good - one dot
const outputDir = context.getScratchDir();

Enforcement Checklist

When reviewing AI-generated code, verify:

• No duplication (G5)
• Clear intent, no magic numbers (G16, G25)
• Polymorphism over conditionals (G23)
• Functions do one thing (G30)
• No Law of Demeter violations (G36)
• Boundary conditions handled (G3)
• Dead code removed (G9)