HOW TO SURVIVE: THE ENDLESS FUN THAT IS LEGACY CODE

The first step of working with legacy code is realising the incredible amount of value that has dropped in you lap.
In this talk we are going to pinpoint that value. And move that value in a better to maintain and understand codebase.

First we will cover the general mentality that will make it easier to prepare a plan of attack.
Next up are more technical tips that will make it easier to talk about the code.
We will end off the session with actually porting a small piece of code.

Transcript

1. HOW TO SURVIVE: HOW TO SURVIVE: THE ENDLESS FUN THE ENDLESS FUN THAT IS LEGACY THAT IS LEGACY CODE CODE
2. FREDERICK FREDERICK VANBRABANT VANBRABANT @maybeFrederick www.frederickvanbrabant.com KEYBOARD FOR HIRE KEYBOARD FOR HIRE
6. "INHERENT VALUE OF THE CODE "INHERENT VALUE OF THE CODE RULES EVERYTHING AROUND ME" RULES EVERYTHING AROUND ME" - THE WU TANG CLAN - THE WU TANG CLAN
7. SO HOW DO WE GET STARTED? SO HOW DO WE GET STARTED?
8. FIRST THINGS FIRST: FIRST THINGS FIRST: MENTALITY MENTALITY
9. DON'T REWRITE DON'T REWRITE
10. “ MOVE FAST AND BREAK MOVE FAST AND BREAK THINGS. UNLESS YOU ARE THINGS. UNLESS YOU ARE BREAKING STUFF, YOU ARE NOT BREAKING STUFF, YOU ARE NOT MOVING FAST ENOUGH. MOVING FAST ENOUGH.
11. “ MOVE FAST AND BREAK MOVE FAST AND BREAK THINGS. UNLESS YOU ARE THINGS. UNLESS YOU ARE BREAKING STUFF, YOU ARE NOT BREAKING STUFF, YOU ARE NOT MOVING FAST ENOUGH. MOVING FAST ENOUGH. - Guy that never worked on legacy code
12. ACT LIKE IT IS OPEN-SOURCE ACT LIKE IT IS OPEN-SOURCE
13. AUTOMATE & ANALYSE AUTOMATE & ANALYSE EVERYTHING EVERYTHING
14. STOP THINKING ABOUT YOUR STOP THINKING ABOUT YOUR FAVOURITE FRAMEWORK FAVOURITE FRAMEWORK
15. NEXT UP: NEXT UP: CODE MINDSET CODE MINDSET
16. KEEP METHODS AND CLASSES KEEP METHODS AND CLASSES SMALL SMALL
17. KEEP PR'S AND COMMITS KEEP PR'S AND COMMITS SMALL SMALL
18. DO CODE REVIEWS DO CODE REVIEWS
19. PAIR PROGRAM AND MENTOR PAIR PROGRAM AND MENTOR
20. DOWN TO BUSINESS: DOWN TO BUSINESS: GETTING STARTED GETTING STARTED
21. GET YOUR BUILDS, GIT AND GET YOUR BUILDS, GIT AND DEPLOYS UNDER CONTROL DEPLOYS UNDER CONTROL
22. USE A DEBUG TOOL USE A DEBUG TOOL
23. USE A FULL ON IDE, USE A FULL ON IDE, No ... seriously
24. WRITE END TO END TESTS. WRITE END TO END TESTS. HEAPS OF THEM HEAPS OF THEM
25. WORK OUTSIDE IN WORK OUTSIDE IN
27. End to end test End to end test End to end test End to end test
28. End to end test End to end test End to end test End to end test Shiny new code
29. End to end test End to end test End to end test End to end test Shiny new code ? ?
30. <?php * A million things * $conn = new mysqli('catInc', 'root', 'hunter2', 'main'); if ($conn->connect_error) { die("Connection failed"); } $sql = "INSERT INTO Cats (name) VALUES ('Thoru')"; $conn->query($sql) $conn->close(); * A million things *
31. <?php class KittenTranslationLayer { public static function addCat($name) { $container = App::getContainer(); $catRepository = $container ->get(CatRepository::class); $catRepository->addCat(new CatName($name)); } }
32. <?php class CatRepository { private $connection; public function __construct(Connection $connection) { $this->connection = $connection; } public function addCat(CatName $name) { $query = $this->connection ->createQueryBuilder(); $query->insert('cats') ->setValue('name', ':name') ->setParameter('name', $name) ->execute();
33. <?php * A million things * $conn = new mysqli('catInc', 'root', 'hunter2', 'main'); if ($conn->connect_error) { die("Connection failed"); } $sql = "INSERT INTO Cats (name) VALUES ('Thoru')"; $conn->query($sql) $conn->close(); * A million things *
34. <?php * A million things * KittenTranslationLayer::addCat('Thoru'); * A million things *
35. NOW ADD ALL THE OTHER NOW ADD ALL THE OTHER TESTS TESTS
36. THE THING ABOUT THE THING ABOUT MICROSERVICES ... MICROSERVICES ...
37. WE AREN'T DONE YET WE AREN'T DONE YET THROW SOME DDD AT IT THROW SOME DDD AT IT
38. ORDER PER DOMAIN NOT PER ORDER PER DOMAIN NOT PER ACTION ACTION
39. App/ ├── Controllers/ │ ├── UserControler.php │ └── PostController.php ├── Models/ │ ├── User.php │ └── Post.php ├── Validators/ │ ├── UserCreate.php │ ├── UserUpdate.php │ ├── PostCreate.php │ └── PostUpdate.php └── Transformers/ ├── User.php └── Post.php
40. App/ ├── Controllers/ │ ├── UserControler.php │ └── PostController.php ├── Models/ │ ├── User.php │ └── Post.php ├── Validators/ │ ├── UserCreate.php │ ├── UserUpdate.php │ ├── PostCreate.php │ └── PostUpdate.php └── Transformers/ ├── User.php └── Post.php App/ ├── Http/ │ ├── UserControler.php │ └── PostController.php ├── User/ │ ├── Validators/ │ ├── ├── Create.php │ ├── └── Update.php │ ├── Transformer.php │ └── User.php └── Post/ ├── Validators/ ├── ├── Create.php ├── └── Update.php ├── Transformer.php └── Post.php
41. ON THAT NOTE: ON THAT NOTE: VALUE OBJECTS VALUE OBJECTS
42. <?php class UserRepository { public function setAmountOfCats(int $amount, int $id) { *code* } }
43. <?php class UserController { private $repo; public function __construct(UserRepository $repo) { $this->repo = $repo; } public function update() { $this->repo->setAmountOfCats(?, ?); } }
44. <?php class UserRepository { public function setAmountOfCats( int $amount, UserId $id ) { *code* } }
45. <?php class UserId implements IdInterface { public function __constructor(int $id) { if ($id < 1) { throw new InvalidIdException(); } $this->id = $id; } public function getValue(); public function getAsUUID(); }
46. GUESS I'M NOW A GUESS I'M NOW A LEGACY CODE LEGACY CODE DEVELOPER DEVELOPER
47. YOU'RE GOING TO SEE SOME YOU'RE GOING TO SEE SOME FUNKY THINGS FUNKY THINGS
48. TRY AND UNDERSTAND WHY TRY AND UNDERSTAND WHY SOMETHING IS DONE SOMETHING IS DONE
49. LEARN MORE? LEARN MORE? Modernizing Legacy Applications In PHP - PM Jones Working Effectively with Legacy Code - Michael Feathers The League of Extraordinary Packages
50. THANKS THANKS
51. QUESTIONS QUESTIONS MAYBEFREDERICK MAYBEFREDERICK