Clean Code Series: Writing Self-Documenting Code

When reading code, the what should be obvious, the how should be discoverable, and the why should be rare but justified.

In this post, we explore the concept of self-documenting code: code that clearly communicates its purpose without relying on excessive or outdated comments. This is a foundational principle of clean, maintainable software.

1. What is Self-Documenting Code?

Self-documenting code communicates intent through structure, naming, and clarity, eliminating the need for most comments.

It relies on:

• Descriptive names for variables, functions, and types
• Clear logic flow and readable control structures
• Well-structured abstractions that group behavior meaningfully

If someone can understand what your code does without reading a comment, that’s self-documenting.

Example:

// Bad: requires comment to clarify intent
// Check if user is an admin
if u.Role == 1 {
    // ...
}

// Better: self-documenting
if u.IsAdmin() {
    // ...
}

2. The Problem with Excessive or Misleading Comments

Comments aren’t inherently bad—but most are unnecessary, and many are harmful when they fall out of sync with the code.

Common issues:

• Outdated comments:

  "This uses AES-128 encryption" → but the code now uses AES-256.

• Obvious comments:

  i += 1  # Increment i by one  ❌
  

• Noise: comments that clutter rather than clarify.

The more your code relies on comments, the more fragile your understanding becomes over time.

3. When Comments Are Acceptable

Use comments only when the code cannot express something clearly on its own—especially when explaining why, not what.

✅ Acceptable comment use cases:

• Justifying a non-obvious decision

  // Using polling due to webhook unreliability (see issue #123)
  

• Linking to external specifications

  // Follows RFC 7519 for JWT validation
  

• Clarifying complex business rules that can't be modeled directly

In short: comment the why, not the what.

4. How to Make Code Self-Explaining

Achieving self-documenting code is a discipline. These are key strategies:

✅ Use Meaningful Names

Bad:

def calc(d, f): ...

Good:

def calculate_final_price(discount, fees): ...

✅ Keep Functions Small and Focused

Small functions are easier to name and understand.

Bad:

func Process(data []byte) error {
    // parsing, validating, persisting, logging...
}

Good:

func Process(data []byte) error {
    parsed := parseData(data)
    if err := validate(parsed); err != nil { return err }
    return persist(parsed)
}

✅ Use Clear Abstractions

Group related behavior meaningfully.

Instead of:

user.SetRole(1)

Use:

user.PromoteToAdmin()

5. Before and After Example

❌ Before (with unnecessary comment):

# Check if the order total is greater than the discount threshold
if order.total > 100:
    apply_discount(order)

✅ After (self-documenting):

if order.qualifies_for_discount():
    order.apply_discount()

This version is cleaner, more readable, and the comment becomes unnecessary.

6. Key Takeaways

• Comments should be a last resort, not a first instinct.
• Aim to write code that explains itself through naming, structure, and abstraction.
• Use comments only to document intent, non-obvious decisions, or external context.
• Self-documenting code leads to cleaner diffs, easier reviews, and fewer bugs.

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Final Thoughts

Writing self-documenting code isn’t just about style—it’s a communication skill that separates good developers from great ones.

Next time you write a comment, ask yourself: “Could I improve the code instead?”
Your future self—and your team—will thank you.

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📣 Keep the Conversation Going!

What are your challenges or strategies with self-documenting code? Share your thoughts in the comments!

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