Clean Code

Be concise, direct, and solution-focused. Clean code reads like well-written prose — every name reveals intent, every function does one thing, and every abstraction earns its place.

Installation

OpenClaw / Moltbot / Clawbot

npx clawhub@latest install clean-code

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Core Principles

| Principle | Rule | Practical Test |

|-----------|------|----------------|

| SRP | Single Responsibility — each function/class does ONE thing | "Can I describe what this does without using 'and'?" |

| DRY | Don't Repeat Yourself — extract duplicates, reuse | "Have I written this logic before?" |

| KISS | Keep It Simple — simplest solution that works | "Is there a simpler way to achieve this?" |

| YAGNI | You Aren't Gonna Need It — don't build unused features | "Does anyone need this right now?" |

| Boy Scout | Leave code cleaner than you found it | "Is this file better after my change?" |

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Naming Rules

Names are the most important documentation. A good name eliminates the need for a comment.

| Element | Convention | Bad | Good |

|---------|------------|-----|------|

| Variables | Reveal intent | n, d, tmp | userCount, elapsed, activeUsers |

| Functions | Verb + noun | user(), calc() | getUserById(), calculateTotal() |

| Booleans | Question form | active, flag | isActive, hasPermission, canEdit |

| Constants | SCREAMING_SNAKE | max, timeout | MAX_RETRY_COUNT, REQUEST_TIMEOUT_MS |

| Classes | Noun, singular | Manager, Data | UserRepository, OrderService |

| Enums | PascalCase values | 'pending' string | Status.Pending |

Rule: If you need a comment to explain a name, rename it.

Naming Anti-Patterns

| Anti-Pattern | Problem | Fix |

|--------------|---------|-----|

| Cryptic abbreviations (usrMgr, cfg) | Unreadable in 6 months | Spell it out — IDE autocomplete makes long names free |

| Generic names (data, info, item, handler) | Says nothing about purpose | Use domain-specific names that reveal intent |

| Misleading names (getUserList returns one user) | Actively deceives readers | Match name to behavior, or change the behavior |

| Hungarian notation (strName, nCount, IUser) | Redundant with type system | Let TypeScript/IDE show types; names describe purpose |

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Function Rules

| Rule | Guideline | Why |

|------|-----------|-----|

| Small | Max 20 lines, ideally 5-10 | Fits in your head |

| One Thing | Does one thing, does it well | Testable and nameable |

| One Level | One level of abstraction per function | Readable top to bottom |

| Few Args | Max 3 arguments, prefer 0-2 | Easy to call correctly |

| No Side Effects | Don't mutate inputs unexpectedly | Predictable behavior |

Guard Clauses

Flatten nested conditionals with early returns. Never nest deeper than 2 levels.

// BAD — 5 levels deep
function processOrder(order: Order) {
  if (order) {
    if (order.items.length > 0) {
      if (order.customer) {
        if (order.customer.isVerified) {
          return submitOrder(order);
        }
      }
    }
  }
  throw new Error('Invalid order');
}

// GOOD — guard clauses flatten the structure
function processOrder(order: Order) {
  if (!order) throw new Error('No order');
  if (!order.items.length) throw new Error('No items');
  if (!order.customer) throw new Error('No customer');
  if (!order.customer.isVerified) throw new Error('Customer not verified');

  return submitOrder(order);
}

Parameter Objects

When a function needs more than 3 arguments, use an options object.

// BAD — too many parameters, order matters
createUser('John', 'Doe', 'john@example.com', 'secret', 'admin', 'Engineering');

// GOOD — self-documenting options object
createUser({
  firstName: 'John',
  lastName: 'Doe',
  email: 'john@example.com',
  password: 'secret',
  role: 'admin',
  department: 'Engineering',
});

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Code Structure Patterns

| Pattern | When to Apply | Benefit |

|---------|--------------|---------|

| Guard Clauses | Edge cases at function start | Flat, readable flow |

| Flat > Nested | Any nesting beyond 2 levels | Reduced cognitive load |

| Composition | Complex operations | Small, testable pieces |

| Colocation | Related code across files | Easier to find and change |

| Extract Function | Comments separating "sections" | Self-documenting code |

Composition Over God Functions

// BAD — god function doing everything
async function processOrder(order: Order) {
  // Validate... (15 lines)
  // Calculate totals... (15 lines)
  // Process payment... (10 lines)
  // Send notifications... (10 lines)
  // Update inventory... (10 lines)
  return { success: true };
}

// GOOD — composed of small, focused functions
async function processOrder(order: Order) {
  validateOrder(order);
  const totals = calculateOrderTotals(order);
  const payment = await processPayment(order.customer, totals);
  await sendOrderConfirmation(order, payment);
  await updateInventory(order.items);
  return { success: true, orderId: payment.orderId };
}

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Return Type Consistency

Functions should return consistent types. Use discriminated unions for multiple outcomes.

// BAD — returns different types
function getUser(id: string) {
  const user = database.find(id);
  if (!user) return false;     // boolean
  if (user.isDeleted) return null; // null
  return user;                 // User
}

// GOOD — discriminated union
type GetUserResult =
  | { status: 'found'; user: User }
  | { status: 'not_found' }
  | { status: 'deleted' };

function getUser(id: string): GetUserResult {
  const user = database.find(id);
  if (!user) return { status: 'not_found' };
  if (user.isDeleted) return { status: 'deleted' };
  return { status: 'found', user };
}

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Anti-Patterns

| Anti-Pattern | Problem | Fix |

|--------------|---------|-----|

| Comment every line | Noise obscures signal | Delete obvious comments; comment why, not what |

| Helper for one-liner | Unnecessary indirection | Inline the code |

| Factory for 2 objects | Over-engineering | Direct instantiation |

| utils.ts with 1 function | Junk drawer file | Put code where it's used |

| Deep nesting | Unreadable flow | Guard clauses and early returns |

| Magic numbers | Unclear intent | Named constants |

| God functions | Untestable, unreadable | Split by responsibility |

| Commented-out code | Dead code confusion | Delete it; git remembers |

| TODO sprawl | Never gets done | Track in issue tracker, not code |

| Premature abstraction | Wrong abstraction is worse than none | Wait for 3+ duplicates before abstracting |

| Copy-paste programming | Duplicated bugs | Extract shared logic |

| Exception-driven control flow | Slow and confusing | Use explicit conditionals |

| Stringly-typed code | Typos and missed cases | Use enums or union types |

| Callback hell | Pyramid of doom | Use async/await |

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Pre-Edit Safety Check

Before changing any file, answer these questions to avoid cascading breakage:

| Question | Why |

|----------|-----|

| What imports this file? | Dependents might break on interface changes |

| What does this file import? | You might need to update the contract |

| What tests cover this? | Tests might fail — update them alongside code |

| Is this a shared component? | Multiple consumers means wider blast radius |

File to edit: UserService.ts
├── Who imports this? → UserController.ts, AuthController.ts
├── Do they need changes too? → Check function signatures
└── What tests cover this? → UserService.test.ts

Rule: Edit the file + all dependent files in the SAME task. Never leave broken imports or missing updates.

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Self-Check Before Completing

Before marking any task complete, verify:

| Check | Question |

|-------|----------|

| Goal met? | Did I do exactly what was asked? |

| Files edited? | Did I modify all necessary files, including dependents? |

| Code works? | Did I verify the change compiles and runs? |

| No errors? | Do lint and type checks pass? |

| Nothing forgotten? | Any edge cases or dependent files missed? |

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NEVER Do

1. NEVER add comments that restate the code — if the code needs a comment to explain what it does, rename things until it doesn't
2. NEVER create abstractions for fewer than 3 use cases — premature abstraction is worse than duplication
3. NEVER leave commented-out code in the codebase — delete it; version control exists for history
4. NEVER write functions longer than 20 lines — extract sub-functions until each does one thing
5. NEVER nest deeper than 2 levels — use guard clauses, early returns, or extract functions
6. NEVER use magic numbers or strings — define named constants with clear semantics
7. NEVER edit a file without checking what depends on it — broken imports and missing updates are the most common source of bugs in multi-file changes
8. NEVER leave a task with failing lint or type checks — fix all errors before marking complete

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References

Detailed guides for specific clean code topics:

| Reference | Description |

|-----------|-------------|

| Anti-Patterns | 21 common mistakes with bad/good code examples across naming, functions, structure, and comments |

| Code Smells | Classic code smells catalog with detection patterns — Bloaters, OO Abusers, Change Preventers, Dispensables, Couplers |

| Refactoring Catalog | Essential refactoring patterns with before/after examples and step-by-step mechanics |