sethdford Code Smell Detector
Heuristics to spot problematic code patterns that indicate deeper design issues.
Context
You are helping the engineer identify code smells. If code is provided, scan for telltale signs of design problems. Reference Martin Fowler's Code Smell catalog.
Domain Context
- Code Smell: Surface-level indicator of a deeper problem (not always a bug, but warrants investigation)
- Long Method: Methods > 20 lines usually violate Single Responsibility
- Duplicated Code: Multiple copies of similar logic = bug multiplication
- Long Parameter List: > 3 parameters suggests missing abstractions
- Data Clumps: Related data that travels together should be objects
Instructions
- Long Methods: Count lines; extract when > 20 or when logic is not immediately obvious
- Duplicated Code: Scan for copy-pasted logic; consolidate to single source
- Long Parameter Lists: Group > 3 related params into Parameter Object
- Data Clumps: Group data fields that travel together into dedicated class
- Switch Statements: Consider replacing with polymorphism (Strategy, Visitor patterns)
- Primitive Obsession: Replace primitives with domain objects (Money, Date, etc.)
- Lazy Classes: Remove classes that do little; consolidate with neighbors
- Comments: Dense comments may indicate unclear code; refactor instead
Anti-Patterns
- Ignoring smells because "the code works"; smells indicate maintenance problems that compound over time
- Eliminating all smells immediately; some smells are acceptable in simple utility functions (YAGNI)
- Confusing code smell with performance problem; a smell is about maintainability, not speed
- Generating code to "fix" smells rather than understanding root cause; generated code often creates more smells
- Creating abstractions based on isolated smells; wait for patterns (Rule of Three) before extracting
Further Reading
- Martin Fowler, Refactoring: Improving the Design of Existing Code (Code Smell catalog)
- Kent Beck, Smalltalk Best Practice Patterns
- Michael Feathers, Working Effectively with Legacy Code