I recently joined a company that's using a huge codebase developed over many years, and it's pretty daunting. The code isn't overly complex at first glance, but due to various edge cases that have piled up, some functions have ballooned to 5000 lines with confusing logic. There's also an ongoing issue with bugs, and to make matters worse, I can't rely on any documentation or test cases since everything is vaguely commented, and the naming is pretty nonsensical. I usually find myself spending hours debugging when something goes wrong.
I'm thinking about how to tackle the refactoring process safely and would like some advice. My initial plan involves creating test cases since the expected inputs and flows are unclear. I figured adding detailed logging could help me capture the behavior of the function under different scenarios to generate useful test cases. Once I have those, I believe I can start refactoring the messy if/else statements into smaller, more manageable methods using guard clauses. I'm open to any additional tips or insights from more experienced programmers!
6 Answers
A solid reference for handling legacy code is 'Working Effectively with Legacy Code' by Michael Feathers. I think what you're planning aligns well with his recommendations. It’s a good read if you want some structured advice on this.
If you can avoid rewriting it completely, that’s best. But if you have to refactor, start by wrapping existing functionality with unit tests. Make sure you cover all bases, then follow the red-green-refactor cycle. I've had to do this before, and it can be tough, but it’s worth it.
Your approach is sound. Just remember that refactoring often comes with the risk of introducing new bugs. Focus on creating tests that validate logical outcomes, not just the implementation details, as those tests will serve as your new documentation. This way, you’ll know that your functions produce the correct results without worrying too much about the underlying logic.
Consider using the Strangler Fig Pattern; this allows you to gradually phase out old functionality in a controlled way. Make sure you implement robust monitoring in the old code to catch any unexpected side effects during the transition.
What I've found helpful is to slowly recreate parts of the code into neater snippets. It’s similar to the ship of Theseus idea: if you replace every part of a ship, is it still the same ship? It’s a gradual process, but you'll end up with a cleaner structure.
Totally agree!
That's a great analogy!
It's usually a nightmare to do such a refactor 😂, but if the code is already buggy, your plan sounds smart. Adding logs to verify behavior should help. Have you thought about how the code runs in production? Analytics can provide insight into actual usage, which will help you prioritize what to isolate and refactor first.
Thanks! I'll definitely check that out!