Util Multi File Refactor

Multi-File Refactor

Quick Start

Systematic, token-efficient multi-file refactoring with safety checks. Enforces MultiEdit for 2+ changes per file (30-50% token savings vs sequential Edit).

Most common use case:

User: "Rename function search_code to find_code across the codebase"

→ Discover all occurrences (Grep)
→ Plan changes (group by file)
→ Execute with MultiEdit (2+ changes per file)
→ Update imports/references
→ Validate (run tests, quality gates)

Result: Clean refactor with no broken references

When to Use This Skill

Primary triggers:

• "Rename function/class/variable across codebase"
• "Refactor pattern X to pattern Y"
• "Extract common code to shared module"
• "Move functionality from A to B"
• "Update all usages of X"

Contextual triggers (agent detection):

• Multiple files need same change
• Function/class used in 3+ files
• Pattern repeats across modules
• Cross-file dependency changes

When NOT to use:

• Single file changes (use Edit directly)
• Simple find-replace (use Edit with replace_all)
• Trivial changes (1-2 total edits)

What This Skill Does

Core capabilities:

1. Discovery & Analysis - Find all affected files using Grep/Glob
2. Change Planning - Group changes by file, identify dependencies
3. Token-Efficient Execution - Use MultiEdit for 2+ changes (30-50% savings)
4. Import/Reference Updates - Fix broken imports and references
5. Validation - Run tests and quality gates
6. Reporting - Document changes and validation results

Refactoring Workflow

Phase 1: Discovery & Analysis

Find all affected files:

# Search for function/class usage
grep -r "search_code" src/ --include="*.py"

# Or use Grep tool
pattern: "search_code"
path: src/
output_mode: files_with_matches

Analyze impact:

• Count occurrences per file
• Identify import statements
• Find documentation references
• Check test files

Phase 2: Change Planning

Group changes by file:

File: src/handlers.py (3 changes) - USE MULTIEDIT
File: src/repository.py (2 changes) - USE MULTIEDIT
File: tests/test_search.py (5 changes) - USE MULTIEDIT
File: README.md (1 change) - USE EDIT

Determine execution order:

1. Core implementation files first
2. Dependent files next
3. Tests last
4. Documentation last

Phase 3: Execution

Token optimization rules:

Rule 1: ALWAYS Use MultiEdit for 2+ Edits

# ❌ BAD: Sequential Edit (wastes tokens)
Edit(file="handlers.py", old_string="search_code(query)", new_string="find_code(query)")
Edit(file="handlers.py", old_string="def search_code", new_string="def find_code")
Edit(file="handlers.py", old_string="search_code_handler", new_string="find_code_handler")

# ✅ GOOD: Single MultiEdit (30-50% token savings)
MultiEdit(file="handlers.py", edits=[
    {"old_string": "search_code(query)", "new_string": "find_code(query)"},
    {"old_string": "def search_code", "new_string": "def find_code"},
    {"old_string": "search_code_handler", "new_string": "find_code_handler"}
])

Rule 2: Group Changes by File

• One MultiEdit call per file
• Include ALL changes for that file
• Read file first to verify changes

Rule 3: Read Before Modifying

# Always read first
Read(file_path="src/handlers.py")

# Then modify
MultiEdit(file="src/handlers.py", edits=[...])

Rule 4: Batch Independent Operations

• Run Read calls in parallel
• Run MultiEdit calls in parallel (if files independent)
• Run validation commands sequentially

Phase 4: Import & Reference Updates

Update import statements:

# If function moved or renamed
# OLD: from src.handlers import search_code
# NEW: from src.handlers import find_code

MultiEdit(file="src/app.py", edits=[
    {"old_string": "from src.handlers import search_code",
     "new_string": "from src.handlers import find_code"}
])

Check for broken references:

# Verify old name doesn't exist
grep -r "search_code" src/ --include="*.py"

# Should return empty or only comments/strings

Phase 5: Validation

Run quality gates:

# Type checking
mypy src/

# Linting
ruff check src/

# Tests
pytest tests/

# All must pass before considering refactor complete

Manual verification:

• Test in running application
• Check logs for errors
• Verify documentation updated

Phase 6: Reporting

Generate refactor report:

## Refactor Report: search_code → find_code

### Files Modified: 8
- src/handlers.py (3 changes)
- src/repository.py (2 changes)
- src/models.py (1 change)
- tests/test_search.py (5 changes)
- tests/test_repository.py (2 changes)
- tests/conftest.py (1 change)
- README.md (1 change)
- docs/API.md (1 change)

### Changes Made:
- Function renamed: search_code → find_code
- Imports updated: 6 files
- Tests updated: 3 files
- Documentation updated: 2 files

### Validation:
✅ mypy: 0 type errors
✅ ruff: 0 linting errors
✅ pytest: 42/42 tests passing
✅ grep verification: No old references found

Status: COMPLETE

Common Refactoring Patterns

Pattern 1: Function/Method Rename

# 1. Find all usages
grep -r "old_function_name" src/

# 2. Plan changes (group by file)
# 3. Execute with MultiEdit per file
# 4. Update imports
# 5. Run tests

Pattern 2: Class Rename

# Additional considerations:
# - Update class definition
# - Update all instantiations
# - Update type hints
# - Update docstrings
# - Update imports

Pattern 3: Module/File Move

# 1. Move file: mv old/path.py new/path.py
# 2. Update all imports referencing old path
# 3. Update relative imports in moved file
# 4. Run tests

Pattern 4: Extract Common Code

# 1. Create new shared module
# 2. Move common code to new module
# 3. Update original files to import from new module
# 4. Remove duplicate code
# 5. Run tests

Pattern 5: API Signature Change

# Example: Add parameter to function
# 1. Update function definition
# 2. Update all call sites (add new parameter)
# 3. Update tests
# 4. Update documentation

Language-Specific Guidance

Python

• Update __init__.py imports
• Fix relative imports (from . import X)
• Update type hints
• Check for dynamic imports (importlib)

JavaScript/TypeScript

• Update named imports: import { oldName } from 'module'
• Update default imports: import oldName from 'module'
• Update require statements: const oldName = require('module')
• Update type definitions (.d.ts files)

Java

• Update package imports
• Update fully qualified names
• Rebuild project (Maven/Gradle)
• Update XML configuration files

Go

• Update package imports
• Run go mod tidy
• Update interface implementations
• Run go build

Validation Checklist

After refactoring, verify:

• All quality gates passing (mypy, ruff, pytest)
• No grep results for old name (except comments/strings if intended)
• All imports updated
• Tests passing (unit, integration, E2E)
• Documentation updated (README, API docs)
• No broken references in other files
• Application runs without errors
• Logs show no warnings/errors

Anti-Patterns to Avoid

1. Sequential Edit on Same File - Use MultiEdit for 2+ changes (30-50% token savings)
2. Blind Editing Without Reading - Always Read file first to verify context
3. Skipping Tests - Tests catch broken references immediately
4. Ignoring Quality Gates - Type errors indicate missed references
5. Forgetting Imports - Broken imports cause runtime errors
6. Incomplete Refactoring - Leaving old name in some files creates confusion
7. Wrong Dependency Order - Update core files before dependent files

Edge Cases & Troubleshooting

Pattern in Strings/Comments

Issue: Grep finds occurrences in strings/comments that shouldn't be changed

Solution:

• Review grep results manually
• Exclude string/comment matches from changes
• Use more specific search patterns (e.g., def search_code instead of just search_code)

Partial Matches

Issue: "search_code" also matches "search_code_advanced"

Solution:

• Use word boundaries in grep: \bsearch_code\b
• Review all matches before changing
• Use more specific old_string in Edit/MultiEdit

Tests Failing After Refactor

Issue: Tests fail with "NameError" or "ImportError"

Diagnosis:

# Check for old references
grep -r "old_name" tests/

# Check import statements
grep -r "from.*import.*old_name" tests/

Solution:

• Update test imports
• Update test fixture names
• Update mock/patch references

MultiEdit Conflicts

Issue: MultiEdit fails with "overlapping edits" or "string not found"

Diagnosis:

• Edits are in wrong order
• String changed between Read and MultiEdit
• old_string not unique

Solution:

• Ensure old_strings are unique
• Order edits top-to-bottom in file
• Re-read file if it changed

Expected Outcomes

Successful Refactor

## Refactor Complete

Files Modified: 12
Total Changes: 37
Token Efficiency: 45% savings (MultiEdit vs Edit)

Validation:
✅ Type checking: 0 errors
✅ Linting: 0 issues
✅ Tests: 87/87 passing
✅ Verification: No old references

Status: READY TO COMMIT

Failed Validation

## Refactor Failed Validation

Files Modified: 12
Total Changes: 37

Validation:
❌ Tests: 3 failures
  - test_search_handler: ImportError: cannot import 'search_code'
  - test_repository: NameError: 'search_code' not defined
❌ Grep verification: 2 old references found
  - src/cache.py:45: search_code_cache
  - tests/conftest.py:12: mock_search_code

Action Required:
1. Fix remaining imports in test files
2. Update cache.py reference
3. Update conftest.py fixture
4. Re-run validation

Status: BLOCKED

Supporting Files

• references/refactoring-guide.md - Comprehensive guidance:
  • Detailed refactoring patterns (10+ scenarios)
  • Language-specific best practices (Python, JS/TS, Java, Go, Rust)
  • Token optimization calculations and examples
  • Advanced edge cases and solutions
  • Quality gate configuration details

Red Flags to Avoid

1. Using Edit for 2+ changes - Wastes 30-50% tokens
2. Skipping Read before Edit - Causes edit failures
3. Incomplete refactoring - Partial changes break codebase
4. Ignoring test failures - Broken references in production
5. Not verifying old references gone - grep should return empty
6. Forgetting documentation - README/API docs out of sync
7. Skipping quality gates - Type errors indicate missed updates
8. Wrong execution order - Dependencies before dependents causes failures

Key principle: Token-efficient refactoring uses MultiEdit for 2+ changes (30-50% savings) while maintaining safety through validation.

Remember: 10 minutes of systematic refactoring prevents hours of debugging broken references.