Dead Code Removal
This skill safely identifies and removes unused code across multiple programming languages. It includes comprehensive safety checks to prevent removing code that's actually needed.
When to Use This Skill
- After refactoring code and removing features
- Before production deployment to reduce bundle size
- When cleaning up legacy code
- When removing deprecated functionality
- When optimizing codebase size
- When maintaining code quality standards
What This Skill Does
- Language Detection: Identifies project languages and structure
- Entry Point Mapping: Maps entry points and critical paths
- Dependency Analysis: Builds dependency graphs and usage patterns
- Safe Detection: Identifies unused elements with safety checks
- Incremental Removal: Removes code incrementally with validation
- Backup Creation: Creates backups before making changes
Helper Scripts
This skill includes Python helper scripts in scripts/:
-
find_unused_imports.py: Uses AST parsing to accurately detect unused imports in Python files. Outputs JSON with unused imports and line numbers.
python scripts/find_unused_imports.py src/utils.py src/services.py
How to Use
Remove Unused Code
Find and remove unused imports and functions in this project
Clean up dead code in src/ directory, but be conservative
Specific Analysis
Check for unused functions in src/utils/ and remove them safely
Analysis Process
1. Language Detection
Identify Project Type:
- Python: Look for
pyproject.toml, setup.py, requirements.txt
- JavaScript/TypeScript: Check
package.json, tsconfig.json
- Java: Look for
pom.xml, build.gradle
- Go: Check
go.mod
- Rust: Check
Cargo.toml
Detect Entry Points:
- Python:
main.py, __main__.py, app.py, run.py
- JavaScript:
index.js, main.js, server.js, app.js
- Java:
Main.java, *Application.java, *Controller.java
- Config files:
*.config.*, settings.*, setup.*
- Test files:
test_*.py, *.test.js, *.spec.js
2. Build Dependency Graph
Cross-File Dependencies:
- Track imports and requires
- Map function/method calls
- Identify class inheritance
- Track dynamic usage patterns
Framework Patterns:
- Preserve framework-specific patterns (Django models, React components, etc.)
- Check for decorators and annotations
- Verify entry point registrations
3. Detect Unused Elements
Using Helper Script:
The skill includes a Python helper script for finding unused imports:
python scripts/find_unused_imports.py src/utils.py src/services.py
Unused Imports:
import ast
Unused Functions/Classes:
- Define: All declared functions/classes
- Reference: Direct calls, inheritance, callbacks
- Preserve: Entry points, framework hooks, event handlers
4. Safety Checks
Never Remove If:
- Python:
getattr(), eval(), globals() usage detected
- JavaScript:
window[], this[], dynamic import() usage
- Java: Reflection, annotations (
@Component, @Service)
- Framework patterns: Models, controllers, routes, components
- Entry points: Main functions, app initialization
- Test files: All test-related code
Framework Preservation:
Python:
- Django: Models, migrations, admin registrations
- Flask: Routes, blueprints, app factories
- FastAPI: Endpoints, dependencies
JavaScript:
- React: Components, hooks, context providers
- Vue: Components, directives, mixins
- Angular: Decorators, services, modules
Java:
- Spring: Beans, controllers, repositories
- JPA: Entities, repositories
5. Safe Removal Process
Backup Creation:
backup_dir="./unused_code_backup_$(date +%Y%m%d_%H%M%S)"
cp -r . "$backup_dir" 2>/dev/null || mkdir -p "$backup_dir" && rsync -a . "$backup_dir"
Incremental Removal:
- Create temp file with change
- Validate syntax
- Run tests if available
- Apply or rollback
Validation:
python -m py_compile file.py
python -m pytest
npx eslint file.js
npm test
javac -Xlint file.java
mvn test
Examples
Example 1: Remove Unused Imports
Input: Clean up unused imports in src/utils/helpers.py
Output:
## Dead Code Removal: src/utils/helpers.py
### Analysis
- **File**: `src/utils/helpers.py`
- **Total imports**: 8
- **Unused imports**: 3
### Unused Imports Found
1. `import os` - Line 2 (not used anywhere)
2. `import json` - Line 3 (not used anywhere)
3. `from datetime import timedelta` - Line 5 (not used anywhere)
### Safe to Remove
✅ All 3 imports are safe to remove (no dynamic usage detected)
### Changes
```python
# Before
import os
import json
from datetime import datetime, timedelta
import requests
# After
from datetime import datetime
import requests
Validation
- ✅ Syntax check passed
- ✅ Tests pass
- ✅ No dynamic imports detected
### Example 2: Remove Unused Functions
**Input**: Find unused functions in `src/services/`
**Output**:
```markdown
## Dead Code Removal: src/services/
### Analysis
- **Files analyzed**: 12
- **Functions found**: 45
- **Unused functions**: 2
### Unused Functions
**1. `formatOldDate()` in `src/services/utils.js`**
- **Location**: Line 34-42
- **Status**: ✅ Safe to remove
- **Reason**: No references found, not exported, not used in tests
**2. `legacyAuth()` in `src/services/auth.js`**
- **Location**: Line 78-95
- **Status**: ⚠️ Preserved (framework pattern)
- **Reason**: Referenced in route configuration (line 12)
### Summary
- **Removed**: 1 function (`formatOldDate`)
- **Preserved**: 1 function (framework usage)
- **Lines removed**: 9
- **Size reduction**: ~300 bytes
Best Practices
Safety Guidelines
Do:
- Run tests after each removal
- Preserve framework patterns
- Check string references in templates
- Validate syntax continuously
- Create comprehensive backups
- Remove incrementally
Don't:
- Remove without understanding purpose
- Batch remove without testing
- Ignore dynamic usage patterns
- Skip configuration files
- Remove from migrations
- Remove exported/public APIs
Detection Patterns
Static Analysis:
- Use AST parsing for accurate detection
- Track cross-file references
- Check for dynamic usage patterns
- Verify framework-specific patterns
Validation:
- Always run syntax checks
- Run tests after removal
- Verify build still works
- Check for runtime errors
Reporting
Report Should Include:
- Files analyzed (count and types)
- Unused detected (imports, functions, classes)
- Safely removed (with validation status)
- Preserved (reason for keeping)
- Impact metrics (lines removed, size reduction)
Related Use Cases
- Code cleanup before release
- Reducing bundle size
- Removing deprecated code
- Maintaining code quality
- Refactoring legacy codebases
- Optimizing build times
