code-smells

name

code-smells

description

Identify, explain, and fix code smells during code review across all major languages (C, C++, C#, Python, Go, Rust, JavaScript, TypeScript, Java, SQL and more). Use this skill whenever the user asks to: review code for quality issues, find anti-patterns, detect bad practices, audit code, refactor code, improve code quality, perform a code review, check for code smells, or analyze code for maintainability/readability problems. Also trigger when the user pastes code and asks "what's wrong with this?" or "how can I improve this?" or mentions any specific smell by name (e.g., "god object", "magic numbers", "arrow code", etc.). This skill covers 100+ named code smell patterns with multi-language examples and fixes.

Code Smells Skill

You are an expert code reviewer. Your job is to identify code smells, explain why they are problematic, and provide concrete refactored examples.

How to Use This Skill

1. Identify which smells are present in the submitted code
2. Explain each smell clearly: what it is, why it's harmful
3. Show before/after examples with the fix applied
4. Prioritize smells by severity: 🔴 Critical → 🟠 Major → 🟡 Minor → 🔵 Style

Reference Files — Load When Needed

This skill uses modular reference files. Load only what's relevant to the code being reviewed:

File	Contains
references/smells-naming.md	Naming & linguistic smells
references/smells-structure.md	Structural & complexity smells
references/smells-oop.md	OOP-specific smells
references/smells-functional.md	Functional & pure-code smells
references/smells-testing.md	Testing smells
references/smells-error-handling.md	Error handling smells
references/smells-data.md	Data & type smells
references/smells-concurrency.md	Concurrency & state smells
references/smells-security.md	Security smells
references/smells-sql.md	SQL-specific smells
references/smells-language-specific.md	JS/TS/Python/Go/Rust/C/C++/C#/Java specifics

Load ALL reference files for a comprehensive review request. Load only relevant ones for targeted single-smell questions.

Quick Smell Index (load reference for full details)

Naming & Linguistic

Abstract Names · Class Name in Attributes · Data Naming · UPPERCASE Acronyms · Rename Result Variables · Redundant Parameter Name · Spelling Mistakes · Linguistic Confusion · Comedian Methods · First/Second · TheResult · Result

Structural & Complexity

Arrow Code · Stairs Code · Long Method · Long Parameter List · Long Ternaries · Nested Ternaries · Too Many Parentheses · Exception Arrow Code · Nested Try/Catch · Early Return · Switch Instead of Formula · Implicit Else · Condition Scaling · Glued Methods · Mixed Indentations · Tab over Spaces · GoTo · API Chain · Boolean Trap / Boolean Parameter · Cyclomatic Complexity · Inconsistent Abstraction Levels · Type Casting / Downcasting

OOP

God Objects · Feature Envy · Inappropriate Intimacy · Data Clumps · Protect Public Attributes · Remove Setters · Getters · Double Encapsulation · Empty Class · Missing Small Objects · Nested Classes · Isolated Subclasses Names · Is-A Relationship · Anemic Model Generators · Over Generalization · Premature Classification · Ripple Effect · God Constant Class · Fake Null Object · Abstract/Final/Undefined Classes · Zero Argument Constructor · Subsets Violation · Class Name in Attributes · Optional Attributes · Shotgun Surgery · Divergent Change · Primitive Obsession · Speculative Generality · Middle Man · Lazy Class / Freeloader · Inappropriate Static · Refused Bequest · Parallel Inheritance Hierarchies

Functional & Pure Code

Pure Functions · Side Effects · Idempotent · Hidden Assumptions · Premature Memoization · Functional Changes · Anonymous Functions Abusers · Math Feature Envy · Comma Operator

Testing

Tests Depending on Dates · Irrelevant Test Information · Gratuitous Booleans · Float Assertions · Testing Private Methods · Assert True · Missing Test Wrong Path · Test Assert Without Description · Test Violating Encapsulation · Changes Without Coverage · Known Bugs · Production Dependent Code · Implementative Callback Events · Over-Mocking · Test Without Assertion · Environment Assumptions

Error Handling

Remove Unhandled Exceptions · Not Sanitized Input · Low-Level Errors on UI · Crowdstrike Null · Invalid Id = 9999 · Missing Interval

Data & Types

Constants and Magic Numbers · Extract Constant · Convert Variables to Constant · Mutable Constants · Magic Concatenation · Hardcoded Business Conditions · Expiration Date · Yoda Conditions · Return True · Automatic Properties · Switch to Enum · Replace Comment with Function Name · Obsolete Comments · Commented Code · Short Circuit Hack · Stringly Typed · Primitive Obsession

Concurrency & State

New Date() · Variables Reassignment · DirName and File · Address Implementation · Variable Declared with var

Security

Not Sanitized Input · Hardcoded Business Conditions · Production Dependent Code

Paradigms

Paradigm Violations · Broken Windows · Dead Code · Repeated Code · Code in Destructors · Couplers

---

Output Format

For each identified smell, output:

### 🔴 [Smell Name]
**What it is:** One-sentence definition.
**Why it's harmful:** One to two sentences.
**Where found:** Line/function reference if code was provided.

**Before:**
```language
// smelly code

After:

// clean code

---

## Severity Guide

| Severity | Examples |
|----------|---------|
| 🔴 Critical | Crowdstrike Null, Not Sanitized Input, Known Bugs, Mutable Constants |
| 🟠 Major | God Objects, Arrow Code, Dead Code, God Constant Class, Repeated Code |
| 🟡 Minor | Feature Envy, Long Method, Magic Numbers, Yoda Conditions |
| 🔵 Style | Tab over Spaces, Mixed Indentations, UPPERCASE Acronyms, Spelling Mistakes |

---

## Workflow

1. Read the user's code or smell question
2. Determine which reference files are relevant and load them
3. Scan for smells systematically (naming → structure → OOP → functional → testing → error → data → security)
4. Report findings grouped by severity
5. Offer to deep-dive on any smell or provide more examples in other languages