Refactoring Code

Refactoring Code

MCP Tools

Serena (safe refactoring):

• find_symbol — Locate refactoring targets
• find_referencing_symbols — Find ALL usages before changes
• rename_symbol — Rename across entire codebase safely
• replace_symbol_body — Replace function implementations
• get_symbols_overview — Understand module structure

The Refactoring Hat

When refactoring, you change structure without changing behavior. Always have tests passing before and after.

Workflows

• Tests Green: Ensure all tests pass before starting
• Analyze: Use Serena to understand dependencies
• Small Steps: Make one small change at a time
• Verify Usages: Use find_referencing_symbols before changes
• Commit Often: Commit after each successful refactoring
• Tests Green: Verify tests still pass after each change

Common Refactorings

Extract Method

When a code block does one thing, extract it to a named method.

1. Use find_referencing_symbols to verify extraction won't break callers
2. Extract the method
3. Run tests

Rename for Clarity

Names should reveal intent.

1. Use find_referencing_symbols to find ALL usages
2. Use rename_symbol for codebase-wide rename
3. Verify no missed references

Remove Dead Code

1. Use find_referencing_symbols to verify code is unused
2. If zero references, safe to remove
3. If references exist, trace to understand usage

Code Smells to Address

• Long Method: Extract smaller methods
• Long Parameter List: Introduce parameter object
• Duplicate Code: Extract to shared function (use find_symbol to locate duplicates)
• Feature Envy: Move method to the class it uses most
• Data Clumps: Group related data into objects
• Primitive Obsession: Replace primitives with value objects

Safety Rules

1. Never refactor and add features simultaneously
2. Always use find_referencing_symbols before removing/renaming
3. Run tests after every change
4. Use Serena's rename_symbol instead of find-replace
5. Commit working states frequently