Clean Code Skill

This skill embodies the principles of "Clean Code" by Robert C. Martin (Uncle Bob). Use it to transform "code that works" into "code that is clean."

🧠 Core Philosophy

"Code is clean if it can be read, and enhanced by a developer other than its original author." — Grady Booch

When to Use

Use this skill when:

Writing new code: To ensure high quality from the start.
Reviewing Pull Requests: To provide constructive, principle-based feedback.
Refactoring legacy code: To identify and remove code smells.
Improving team standards: To align on industry-standard best practices.

1. Meaningful Names

Use Intention-Revealing Names: elapsedTimeInDays instead of d.
Avoid Disinformation: Don't use accountList if it's actually a Map.
Make Meaningful Distinctions: Avoid ProductData vs ProductInfo.
Use Pronounceable/Searchable Names: Avoid genymdhms.
Class Names: Use nouns (Customer, WikiPage). Avoid Manager, Data.
Method Names: Use verbs (postPayment, deletePage).

2. Functions

Small!: Functions should be shorter than you think.
Do One Thing: A function should do only one thing, and do it well.
One Level of Abstraction: Don't mix high-level business logic with low-level details (like regex).
Descriptive Names: isPasswordValid is better than check.
Arguments: 0 is ideal, 1-2 is okay, 3+ requires a very strong justification.
No Side Effects: Functions shouldn't secretly change global state.

3. Comments

Don't Comment Bad Code—Rewrite It: Most comments are a sign of failure to express ourselves in code.

Explain Yourself in Code:

# Check if employee is eligible for full benefits
if employee.flags & HOURLY and employee.age > 65:

if employee.isEligibleForFullBenefits():

Good Comments: Legal, Informative (regex intent), Clarification (external libraries), TODOs.
Bad Comments: Mumbling, Redundant, Misleading, Mandated, Noise, Position Markers.

4. Formatting

The Newspaper Metaphor: High-level concepts at the top, details at the bottom.
Vertical Density: Related lines should be close to each other.
Distance: Variables should be declared near their usage.
Indentation: Essential for structural readability.

5. Objects and Data Structures

Data Abstraction: Hide the implementation behind interfaces.
The Law of Demeter: A module should not know about the innards of the objects it manipulates. Avoid a.getB().getC().doSomething().
Data Transfer Objects (DTO): Classes with public variables and no functions.

6. Error Handling

Use Exceptions instead of Return Codes: Keeps logic clean.
Write Try-Catch-Finally First: Defines the scope of the operation.
Don't Return Null: It forces the caller to check for null every time.
Don't Pass Null: Leads to NullPointerException.

7. Unit Tests

The Three Laws of TDD:
1. Don't write production code until you have a failing unit test.
2. Don't write more of a unit test than is sufficient to fail.
3. Don't write more production code than is sufficient to pass the failing test.
F.I.R.S.T. Principles: Fast, Independent, Repeatable, Self-Validating, Timely.

8. Classes

Small!: Classes should have a single responsibility (SRP).
The Stepdown Rule: We want the code to read like a top-down narrative.

9. Smells and Heuristics

Rigidity: Hard to change.
Fragility: Breaks in many places.
Immobility: Hard to reuse.
Viscosity: Hard to do the right thing.
Needless Complexity/Repetition.

🛠️ Implementation Checklist

Is this function smaller than 20 lines?
Does this function do exactly one thing?
Are all names searchable and intention-revealing?
Have I avoided comments by making the code clearer?
Am I passing too many arguments?
Is there a failing test for this change?

Example

User request:

Refactor this working code for clearer names, smaller units, explicit errors, and preserved behavior; verify it with focused tests.

Limitations

Use this skill only when the task clearly matches the scope described above.
Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.

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