Working effectively with legacy code isn’t all about creating test harnesses before refactoring algorithms. The “safety first” strategy doesn’t always apply. Not if the code you’re looking at is LYING IN YOUR FACE anyway. In this talk I’ll show you what brutal refactoring is. I’ll show you the red glowy eyes of the Churn. And I’ll hold up some big warning signs that should prevent you from producing legacy code today. Table flips allowed.

1. Brutal Refactoring
Lying Code
The Churn
(and other emotional stories from)
Legacy Land!
Matthias Noback
@matthiasnoback

2. ( °□°╯ ）╯︵ ┻━┻

3. (Maintaining) legacy code is depressing

4. “Technical debt”

5. “Continuous
improvement”

6. What can I know?

7. Besides outdated languages, old libraries, and
frameworks you no longer understand...

8. Domain knowledge has left the building
if ($product->isGrewBilly() && $customer->prefersPayTotum()) {
$this->emailManager->sendTotumBillyAnnuitySummary();
}

9. Nobody knows why anymore

10. "Code should be self-documenting"

11. Please add comments

12. if (invoiceLinesHaveDifferentVatRates) {
vatAmount = sumOfNetAmountsOnInvoiceLines * vatRate;
} else {
vatAmount = sumOfVatAmountsOnInvoiceLines;
}

13. "Legacy code is code without an owner"

14. So... what should I do?

15. Read books

21. The Churn.

24. Core domain concepts

26. Guess: who are the monsters in your project?

27. Scaring away Churn monsters is a lot of work too!

29. Create invoice
From time
writing
From
contracts
From
sales order
Create
credit
invoice
Update sales
order status
Sales order
stuff

30. Brutal refactoring

31. What else... should I do?

34. Little things?

35. Weed the ground

36. Pick up the stones, then put them back

37. Look your monster in the eyes

38. “Could this go somewhere else?”

39. What may I hope?

40. How did we get here?

41. Different developers
Changing landscape
Bad management
Bad developers

43. You know what to do...
● Write tests from the start
● Document code and architecture decisions
● Agree on a coding style
● Enforce a coding standard
● Run static analysis tools
And so on...

44. You can hope that people will do this from now on
(actually, force them...)

45. The secret: most code could remain untouched

46. Consolidate

47. Not everything needs “consolidation”

49. Again … What may I hope?

51. Naive?

52. This is it

53. Do what you can do

55. “Burnout”

57. This is it