1. Tackling
Tech Debt
with Rector

2. Michele Orselli
Eng Manager@Spreaker
_orso_
micheleorselli
michele.orselli@spreaker.com

3. ● Spreaker is a podcast platform
● Within Spreaker, podcasts can be
hosted, distributed, monetized,
discovered, and listened to
● Part of iHeartMedia family since
2020

4. 🤓 Expert teams can tame it, choosing willingly
to accumulate it
→ trade off cleaner solution with a good
enough one
Tech Debt
🐥 Green teams accumulate it unconsciously
→ let's try this and that
Never saw a project without it 🙄

5. The mere fact that
we are writing code
exposes us to tech debt
Tech Debt
-> Language Evolves
-> Libraries evolve
-> Frameworks evolve
-> Things are (re)discovered

6. How can we deal with it?
Invest 🕒 and ⚡
to repay the debt
😫 Sometimes it is hard
to justify the investment
🤔 Is there a way to get away
with it?
Tech Debt

7. Performs automated refactorings on a codebase
It provides a list of predefined rectors, aka rules, refactorings you can choose
to apply on your codebase, via a rector.php config file. E.g.
- Change a property access with a method call
from $obj->property to $obj->method()
- Substitute class invocation with another one
from Banana::method() to Apple::anotherMethod()
Rector

8. Provided a ton of rules out of the box
- Code style/quality
- Manipulate properties/methods
- Upgrade language version
- Upgrade framework version
Rector
https://github.com/rectorphp/rector/blob/main/docs/rector_rules_overview.md

9. Why do I need it?
-> Regexp are not enough?
-> Search and replace is not enough?
Rectors parses the code, so it can perform complex manipulation. For this
reason it is also unaffected by code formatting (spaces, newlines, …)
Rector

10. Installation/configuration
$ composer require rector/rector --dev
If you create custom rules, configure composer.json to enable autoload
"autoload-dev": {
"psr-4": {
"UtilsRector": "tools/php/rector/src",
"UtilsRectorTests": "tools/php/rector/tests"
}
}

11. Installation/configuration
Create an empty rector.php file in the project root directory
$ vendor/bin/rector init
Change rector.php to specify which directories should be scanned and which
rules should be applied

12. rector.php
<?php
return static function (RectorConfig $rectorConfig): void {
$rectorConfig->paths([
__DIR__ . '/apps',
__DIR__ . '/lib',
__DIR__ . '/test',
]);
$rectorConfig->rule(AddContainerAwareIfNotPresent::class);
$rectorConfig->rule(MigrateSpUtilStaticCallsRector::class);
};

13. Run
In the project root directory run
$ vendor/bin/rector process
If you want to see a preview of the changes without touching the files
$ vendor/bin/rector process --dry-run

14. Rules

15. RectorPhp74RectorPropertyTypedPropertyRector
TypedPropertyRector

16. RectorPhp80RectorClass_StringableForToStringRector
StringableForToStringRector

17. RectorPhp82RectorFuncCallUtf8DecodeEncodeToMbConvertEncodingRector
Utf8DecodeEncodeToMbConvertEncodingRector

18. Configurable Rules
Rule accepting configuration params

19. RectorTransformRectorClass_AddAllowDynamicPropertiesAttributeRector
AddAllowDynamicPropertiesAttributeRector

20. SetLists
Define a group of rules to avoid specify them one by one

21. rector.php
<?php
return static function (RectorConfig $rectorConfig): void {
$rectorConfig->paths([
__DIR__ . '/apps',
__DIR__ . '/lib',
__DIR__ . '/test',
]);
$rectorConfig->sets([SetList::DEAD_CODE, SetList::PHP_82]);
};

22. LevelSetLists
Applies all the rules up to a certain PHP version

23. rector.php
<?php
return static function (RectorConfig $rectorConfig): void {
$rectorConfig->paths([
__DIR__ . '/apps',
__DIR__ . '/lib',
__DIR__ . '/test',
]);
$rectorConfig->sets([LevelSetList::UP_TO_PHP_82]);
};

24. 1. Loads configuration from rector.php
2. Iterates all files
3. For each file
a. Preparation phase: parse file, creates AST (array of nodes), add some
metadata
b. Rectify Phase
i. Traverse AST
ii. Check if rectors can be applied to that node
iii. If yse, apply
c. Save/Diff phase
How it works

25. A rule is a PHP class that extends AbstractRector
Implement 3 method
Writing Custom Rules
public function getRuleDefinition(): RuleDefinition
public function getNodeTypes(): array
public function refactor(Node $node): ?Node

26. Life of a PHP file 🐘

27. <?php
namespace AppTime;
class Clock
{
public function now()
{
return date('Y-m-d');
}
}

28. <?php
namespace AppTime;
class Clock
{
public function now()
{
return date('Y-m-d');
}
}
T_OPEN_TAG ('<?php')
T_NAMESPACE ('namespace')
T_WHITESPACE (' ')
T_STRING ('App')
T_NS_SEPARATOR ('')
T_STRING ('Time')
T_WHITESPACE (' ')
T_CLASS ('class')
T_WHITESPACE (' ')
T_STRING ('Clock')
T_WHITESPACE (' ')
T_WHITESPACE (' ')
T_PUBLIC ('public')
T_WHITESPACE (' ')
T_FUNCTION ('function')
T_WHITESPACE (' ')
T_STRING ('now')
T_WHITESPACE (' ')
T_WHITESPACE ('')
T_RETURN ('return')
T_WHITESPACE (' ')
T_STRING ('date')
T_CONSTANT_ENCAPSED_STRING
(''Y-m-d'')
T_WHITESPACE ('')
T_WHITESPACE ('')
T_WHITESPACE ('')
Tokenizer

29. <?php
namespace AppTime;
class Clock
{
public function now()
{
return date('Y-m-d');
}
}
T_OPEN_TAG ('<?php')
T_NAMESPACE ('namespace')
T_WHITESPACE (' ')
T_STRING ('App')
T_NS_SEPARATOR ('')
T_STRING ('Time')
T_WHITESPACE (' ')
T_CLASS ('class')
T_WHITESPACE (' ')
T_STRING ('Clock')
T_WHITESPACE (' ')
T_WHITESPACE (' ')
T_PUBLIC ('public')
T_WHITESPACE (' ')
T_FUNCTION ('function')
T_WHITESPACE (' ')
T_STRING ('now')
T_WHITESPACE (' ')
T_WHITESPACE ('')
T_RETURN ('return')
T_WHITESPACE (' ')
T_STRING ('date')
T_CONSTANT_ENCAPSED_STRING
(''Y-m-d'')
T_WHITESPACE ('')
T_WHITESPACE ('')
T_WHITESPACE ('')
Tokenizer

30. <?php
namespace AppTime;
class Clock
{
public function now()
{
return date('Y-m-d');
}
}
T_OPEN_TAG ('<?php')
T_NAMESPACE ('namespace')
T_WHITESPACE (' ')
T_STRING ('App')
T_NS_SEPARATOR ('')
T_STRING ('Time')
T_WHITESPACE (' ')
T_CLASS ('class')
T_WHITESPACE (' ')
T_STRING ('Clock')
T_WHITESPACE (' ')
T_WHITESPACE (' ')
T_PUBLIC ('public')
T_WHITESPACE (' ')
T_FUNCTION ('function')
T_WHITESPACE (' ')
T_STRING ('now')
T_WHITESPACE (' ')
T_WHITESPACE ('')
T_RETURN ('return')
T_WHITESPACE (' ')
T_STRING ('date')
T_CONSTANT_ENCAPSED_STRING
(''Y-m-d'')
T_WHITESPACE ('')
T_WHITESPACE ('')
T_WHITESPACE ('')
Tokenizer

31. <?php
namespace AppTime;
class Clock
{
public function now()
{
return date('Y-m-d');
}
}
T_OPEN_TAG ('<?php')
T_NAMESPACE ('namespace')
T_WHITESPACE (' ')
T_STRING ('App')
T_NS_SEPARATOR ('')
T_STRING ('Time')
T_WHITESPACE (' ')
T_CLASS ('class')
T_WHITESPACE (' ')
T_STRING ('Clock')
T_WHITESPACE (' ')
T_WHITESPACE (' ')
T_PUBLIC ('public')
T_WHITESPACE (' ')
T_FUNCTION ('function')
T_WHITESPACE (' ')
T_STRING ('now')
T_WHITESPACE (' ')
T_WHITESPACE ('')
T_RETURN ('return')
T_WHITESPACE (' ')
T_STRING ('date')
T_CONSTANT_ENCAPSED_STRING
(''Y-m-d'')
T_WHITESPACE ('')
T_WHITESPACE ('')
T_WHITESPACE ('')
Tokenizer

32. <?php
namespace AppTime;
class Clock
{
public function now()
{
return date('Y-m-d');
}
}
T_OPEN_TAG ('<?php')
T_NAMESPACE ('namespace')
T_WHITESPACE (' ')
T_STRING ('App')
T_NS_SEPARATOR ('')
T_STRING ('Time')
T_WHITESPACE (' ')
T_CLASS ('class')
T_WHITESPACE (' ')
T_STRING ('Clock')
T_WHITESPACE (' ')
T_WHITESPACE (' ')
T_PUBLIC ('public')
T_WHITESPACE (' ')
T_FUNCTION ('function')
T_WHITESPACE (' ')
T_STRING ('now')
T_WHITESPACE (' ')
T_WHITESPACE ('')
T_RETURN ('return')
T_WHITESPACE (' ')
T_STRING ('date')
T_CONSTANT_ENCAPSED_STRING
(''Y-m-d'')
T_WHITESPACE ('')
T_WHITESPACE ('')
T_WHITESPACE ('')
Tokenizer

33. <?php
namespace AppTime;
class Clock
{
public function now()
{
return date('Y-m-d');
}
}
T_OPEN_TAG ('<?php')
T_NAMESPACE ('namespace')
T_WHITESPACE (' ')
T_STRING ('App')
T_NS_SEPARATOR ('')
T_STRING ('Time')
T_WHITESPACE (' ')
T_CLASS ('class')
T_WHITESPACE (' ')
T_STRING ('Clock')
T_WHITESPACE (' ')
T_WHITESPACE (' ')
T_PUBLIC ('public')
T_WHITESPACE (' ')
T_FUNCTION ('function')
T_WHITESPACE (' ')
T_STRING ('now')
T_WHITESPACE (' ')
T_WHITESPACE ('')
T_RETURN ('return')
T_WHITESPACE (' ')
T_STRING ('date')
T_CONSTANT_ENCAPSED_STRING
(''Y-m-d'')
T_WHITESPACE ('')
T_WHITESPACE ('')
T_WHITESPACE ('')
Tokenizer

34. <?php
namespace AppTime;
class Clock
{
public function now()
{
return date('Y-m-d');
}
}
T_OPEN_TAG ('<?php')
T_NAMESPACE ('namespace')
T_WHITESPACE (' ')
T_STRING ('App')
T_NS_SEPARATOR ('')
T_STRING ('Time')
T_WHITESPACE (' ')
T_CLASS ('class')
T_WHITESPACE (' ')
T_STRING ('Clock')
T_WHITESPACE (' ')
T_WHITESPACE (' ')
T_PUBLIC ('public')
T_WHITESPACE (' ')
T_FUNCTION ('function')
T_WHITESPACE (' ')
T_STRING ('now')
T_WHITESPACE (' ')
T_WHITESPACE ('')
T_RETURN ('return')
T_WHITESPACE (' ')
T_STRING ('date')
T_CONSTANT_ENCAPSED_STRING
(''Y-m-d'')
T_WHITESPACE ('')
T_WHITESPACE ('')
T_WHITESPACE ('')
Tokenizer

35. <?php
namespace AppTime;
c
class Clock
{
public function now()
{
return date('Y-m-d');
}
}
T_OPEN_TAG ('<?php')
T_NAMESPACE ('namespace')
T_WHITESPACE (' ')
T_STRING ('App')
T_NS_SEPARATOR ('')
T_STRING ('Time')
T_WHITESPACE (' ')
T_CLASS ('class')
T_WHITESPACE (' ')
T_STRING ('Clock')
T_WHITESPACE (' ')
T_WHITESPACE (' ')
T_PUBLIC ('public')
T_WHITESPACE (' ')
T_FUNCTION ('function')
T_WHITESPACE (' ')
T_STRING ('now')
T_WHITESPACE (' ')
T_WHITESPACE ('')
T_RETURN ('return')
T_WHITESPACE (' ')
T_STRING ('date')
T_CONSTANT_ENCAPSED_STRING
(''Y-m-d'')
T_WHITESPACE ('')
T_WHITESPACE ('')
T_WHITESPACE ('')
Tokenizer

36. <?php
namespace AppTime;
c
class Clock
{
public function now()
{
return date('Y-m-d');
}
}
T_OPEN_TAG ('<?php')
T_NAMESPACE ('namespace')
T_WHITESPACE (' ')
T_STRING ('App')
T_NS_SEPARATOR ('')
T_STRING ('Time')
T_WHITESPACE (' ')
T_CLASS ('class')
T_WHITESPACE (' ')
T_STRING ('Clock')
T_WHITESPACE (' ')
T_WHITESPACE (' ')
T_PUBLIC ('public')
T_WHITESPACE (' ')
T_FUNCTION ('function')
T_WHITESPACE (' ')
T_STRING ('now')
T_WHITESPACE (' ')
T_WHITESPACE ('')
T_RETURN ('return')
T_WHITESPACE (' ')
T_STRING ('date')
T_CONSTANT_ENCAPSED_STRING
(''Y-m-d'')
T_WHITESPACE ('')
T_WHITESPACE ('')
T_WHITESPACE ('')
Tokenizer

37. <?php
namespace AppTime;
c
class Clock
{
public function now()
{
return date('Y-m-d');
}
}
T_OPEN_TAG ('<?php')
T_NAMESPACE ('namespace')
T_WHITESPACE (' ')
T_STRING ('App')
T_NS_SEPARATOR ('')
T_STRING ('Time')
T_WHITESPACE (' ')
T_CLASS ('class')
T_WHITESPACE (' ')
T_STRING ('Clock')
T_WHITESPACE (' ')
T_WHITESPACE (' ')
T_PUBLIC ('public')
T_WHITESPACE (' ')
T_FUNCTION ('function')
T_WHITESPACE (' ')
T_STRING ('now')
T_WHITESPACE (' ')
T_WHITESPACE ('')
T_RETURN ('return')
T_WHITESPACE (' ')
T_STRING ('date')
T_CONSTANT_ENCAPSED_STRING
(''Y-m-d'')
T_WHITESPACE ('')
T_WHITESPACE ('')
T_WHITESPACE ('')
Tokenizer
token_get_all

38. T_OPEN_TAG ('<?php')
T_NAMESPACE ('namespace')
T_WHITESPACE (' ')
T_STRING ('App')
T_NS_SEPARATOR ('')
T_STRING ('Time')
T_WHITESPACE (' ')
T_CLASS ('class')
T_WHITESPACE (' ')
T_STRING ('Clock')
T_WHITESPACE (' ')
T_WHITESPACE (' ')
T_PUBLIC ('public')
T_WHITESPACE (' ')
T_FUNCTION ('function')
T_WHITESPACE (' ')
T_STRING ('now')
T_WHITESPACE (' ')
T_WHITESPACE ('')
T_RETURN ('return')
T_WHITESPACE (' ')
T_STRING ('date')
T_CONSTANT_ENCAPSED_STRING
(''Y-m-d'')
T_WHITESPACE ('')
T_WHITESPACE ('')
T_WHITESPACE ('')
Parser

39. T_OPEN_TAG ('<?php')
T_NAMESPACE ('namespace')
T_WHITESPACE (' ')
T_STRING ('App')
T_NS_SEPARATOR ('')
T_STRING ('Time')
T_WHITESPACE (' ')
T_CLASS ('class')
T_WHITESPACE (' ')
T_STRING ('Clock')
T_WHITESPACE (' ')
T_WHITESPACE (' ')
T_PUBLIC ('public')
T_WHITESPACE (' ')
T_FUNCTION ('function')
T_WHITESPACE (' ')
T_STRING ('now')
T_WHITESPACE (' ')
T_WHITESPACE ('')
T_RETURN ('return')
T_WHITESPACE (' ')
T_STRING ('date')
T_CONSTANT_ENCAPSED_STRING
(''Y-m-d'')
T_WHITESPACE ('')
T_WHITESPACE ('')
T_WHITESPACE ('')
Parser

40. T_OPEN_TAG ('<?php')
T_NAMESPACE ('namespace')
T_WHITESPACE (' ')
T_STRING ('App')
T_NS_SEPARATOR ('')
T_STRING ('Time')
T_WHITESPACE (' ')
T_CLASS ('class')
T_WHITESPACE (' ')
T_STRING ('Clock')
T_WHITESPACE (' ')
T_WHITESPACE (' ')
T_PUBLIC ('public')
T_WHITESPACE (' ')
T_FUNCTION ('function')
T_WHITESPACE (' ')
T_STRING ('now')
T_WHITESPACE (' ')
T_WHITESPACE ('')
T_RETURN ('return')
T_WHITESPACE (' ')
T_STRING ('date')
T_CONSTANT_ENCAPSED_STRING
(''Y-m-d'')
T_WHITESPACE ('')
T_WHITESPACE ('')
T_WHITESPACE ('')
Parser
AST:
Abstract
Syntax
Tree
PHP-Parser

41. PHP Vm
AST:
Abstract
Syntax
Tree

42. Compiler
PHP Vm
AST:
Abstract
Syntax
Tree

43. Compiler
PHP Vm
Opcodes
AST:
Abstract
Syntax
Tree

44. Compiler
PHP Vm
Opcodes
AST:
Abstract
Syntax
Tree

45. AST - Abstract Syntax Tree
Intermediate representation of the source code
Machine friendly
Tree structure
Traversing the AST means
traversing the original source code

46. https://phpast.com/

47. https://github.com/rectorphp/php-parser-nodes-docs
PHP-Parser nodes docs

48. A rule is a PHP class that extends AbstractRector
Implement 3 method
Writing Custom Rules
public function getRuleDefinition(): RuleDefinition
public function getNodeTypes(): array
public function refactor(Node $node): ?Node

49. Look for existing rules that perform similar tasks. Use it as a starting point.
Look for helper classes: classes that perform some heavy lifting for you. E.g
pull up a property
There are plenty:
- ClassDependencyManipulator
- ClassInsertManipulator
- NodeFactory
- ParamAnalyzer
Create a small snippet of code to test it with --dry-run
Start with an existing rule

50. Let's 👀 at the code…

51. Look for a rule that does something similar to what you need and use it as a
starting point
This part is a bit time consuming, there are multiple ways to achieve the same
result
Don't try to do too much in a single rule, combine multiple rules
Writing Custom Rules: lesson learned

52. Get all the corner cases is hard, Pareto rulez!
NodeDumper is your friend
Create a Dummy snippet for quick testing
Writing Custom Rules: lesson learned

53. Extensions: composer installable set of rules for specific framework/libraries
These are provided out of the box
https://github.com/rectorphp/rector-symfony
https://github.com/rectorphp/rector-doctrine
https://github.com/rectorphp/rector-phpunit
Extensions

54. That's All Folks!
https://leanpub.com/rector-the-power-of-automated-refactoring
Questions?