Clean code

Robert C. Martin (Uncle Bob) Clean Code Best Practices

Comprehensive software craftsmanship guide based on Robert C. Martin's "Clean Code: A Handbook of Agile Software Craftsmanship", updated with modern corrections where the original 2008 advice has been superseded. Contains 48 rules across 10 categories, prioritized by impact to guide code reviews, refactoring decisions, and new development. Examples are primarily in Java but principles are language-agnostic.

When to Apply

Reference these guidelines when:

• Writing new functions, classes, or modules
• Naming variables, functions, classes, or files
• Reviewing code for maintainability issues
• Refactoring existing code to improve clarity
• Writing or improving unit tests
• Wrapping third-party dependencies

Rule Categories by Priority

Priority	Category	Impact	Prefix
1	Meaningful Names	CRITICAL	name-
2	Functions	CRITICAL	func-
3	Comments	HIGH	cmt-
4	Formatting	HIGH	fmt-
5	Error Handling	HIGH	err-
6	Objects and Data Structures	MEDIUM-HIGH	obj-
7	Boundaries	MEDIUM-HIGH	bound-
8	Classes and Systems	MEDIUM-HIGH	class-
9	Unit Tests	MEDIUM	test-
10	Emergence and Simple Design	MEDIUM	emerge-

Quick Reference

1. Meaningful Names (CRITICAL)

• name-intention-revealing - Use names that reveal intent
• name-avoid-disinformation - Avoid misleading names
• name-meaningful-distinctions - Make meaningful distinctions
• name-pronounceable - Use pronounceable names
• name-searchable - Use searchable names
• name-avoid-encodings - Avoid encodings in names
• name-class-noun - Use noun phrases for class names
• name-method-verb - Use verb phrases for method names

2. Functions (CRITICAL)

• func-small - Keep functions small
• func-one-thing - Functions should do one thing
• func-abstraction-level - Maintain one level of abstraction
• func-minimize-arguments - Minimize function arguments
• func-no-side-effects - Avoid side effects
• func-command-query-separation - Separate commands from queries
• func-dry - Do not repeat yourself

3. Comments (HIGH)

• cmt-express-in-code - Express yourself in code, not comments
• cmt-explain-intent - Use comments to explain intent
• cmt-avoid-redundant - Avoid redundant comments
• cmt-avoid-commented-out-code - Delete commented-out code
• cmt-warning-consequences - Use warning comments for consequences

4. Formatting (HIGH)

• fmt-vertical-formatting - Use vertical formatting for readability
• fmt-horizontal-alignment - Avoid horizontal alignment
• fmt-team-rules - Follow team formatting rules
• fmt-indentation - Respect indentation rules

5. Error Handling (HIGH)

• err-use-exceptions - Separate error handling from happy path
• err-write-try-catch-first - Write try-catch-finally first
• err-provide-context - Provide context with exceptions
• err-define-by-caller-needs - Define exceptions by caller needs
• err-avoid-null - Avoid returning and passing null

6. Objects and Data Structures (MEDIUM-HIGH)

• obj-data-abstraction - Hide data behind abstractions
• obj-data-object-asymmetry - Understand data/object anti-symmetry
• obj-law-of-demeter - Follow the Law of Demeter
• obj-avoid-hybrids - Avoid hybrid data-object structures
• obj-dto - Use DTOs for data transfer

7. Boundaries (MEDIUM-HIGH)

• bound-wrap-third-party - Wrap third-party APIs
• bound-learning-tests - Write learning tests for third-party code

8. Classes and Systems (MEDIUM-HIGH)

• class-small - Keep classes small
• class-cohesion - Maintain class cohesion
• class-organize-for-change - Organize classes for change
• class-isolate-from-change - Isolate classes from change
• class-separate-concerns - Separate construction from use

9. Unit Tests (MEDIUM)

• test-first-law - Follow the three laws of TDD
• test-keep-clean - Keep tests clean
• test-one-assert - One concept per test
• test-first-principles - Follow FIRST principles
• test-build-operate-check - Use Build-Operate-Check pattern

10. Emergence and Simple Design (MEDIUM)

• emerge-simple-design - Follow the four rules of simple design
• emerge-expressiveness - Maximize expressiveness

How to Use

Read individual reference files for detailed explanations and code examples:

• Section definitions - Category structure and impact levels
• Rule template - Template for adding new rules

Reference Files

File	Description
references/_sections.md	Category definitions and ordering
assets/templates/_template.md	Template for new rules
metadata.json	Version and reference information