martin-clean-code

Apply the Extract Till You Drop technique: extract until each function does one thing at one level of abstraction, rarely exceeding 20 lines. Use the TO-paragraph test to verify single responsibility, and follow the Stepdown Rule so the file reads top-down by descending abstraction.

Clean Code ranks argument counts as 0 > 1 > 2 > 3, with three or more requiring strong justification. Boolean flag arguments should be split into two functions, output arguments should be replaced with this, and argument clusters that travel together should be wrapped into an object.

Use unchecked exceptions rather than return codes, which clutter callers and violate Command Query Separation. Extract try/catch bodies into their own functions, never return or pass null, and use the Special Case pattern or empty collections for exceptional paths.

It covers all 17 chapters: naming, functions, comments, formatting, objects vs data structures, error handling, boundaries, unit tests, classes, systems, emergence, concurrency, successive refinement, and the full smells and heuristics catalog. It includes a glossary, patterns list, and decision cheatsheet.

The skill covers book content only and does not replace project-specific judgment or tooling. Some rules are context-dependent, such as file size guidelines being desirable rather than hard limits, and the unchecked-exceptions stance being Martin's trade-off judgment for general applications.