Dead code detector for PHP

PHPStan extension to find unused PHP code in your project with ease!

Summary:

• ✅ PHPStan extension
• ♻️ Dead cycles detection
• 🔗 Transitive dead method detection
• 🧹 Automatic removal of unused code
• 📚 Popular libraries support
• ✨ Customizable entrypoints

Installation:

composer require --dev shipmonk/dead-code-detector

Use official extension-installer or just load the rules:

includes:
    - vendor/shipmonk/dead-code-detector/rules.neon

Supported libraries

• Any overridden method that originates in vendor is not reported as dead
• We also support many magic calls in following libraries:

Symfony:

• constructor calls for DIC services!
  • phpstan/phpstan-symfony with containerXmlPath must be used
• #[AsEventListener] attribute
• #[AsController] attribute
• #[AsCommand] attribute
• #[Required] attribute
• #[Route] attributes
• onKernelResponse, onKernelRequest, etc

Doctrine:

• #[AsEntityListener] attribute
• Doctrine\ORM\Events::* events
• Doctrine\Common\EventSubscriber methods
• lifecycle event attributes #[PreFlush], #[PostLoad], ...

PHPUnit:

• data provider methods
• testXxx methods
• annotations like @test, @before, @afterClass etc
• attributes like #[Test], #[Before], #[AfterClass] etc

PHPStan:

• constructor calls for DIC services (rules, extensions, ...)

Nette:

• handleXxx, renderXxx, actionXxx, injectXxx, createComponentXxx
• SmartObject magic calls for @property annotations

All those libraries are autoenabled when found within your composer dependencies. If you want to force enable/disable some of them, you can:

# phpstan.neon.dist
parameters:
    shipmonkDeadCode:
        entrypoints:
            phpunit:
                enabled: true

Customization:

• If your application does some magic calls unknown to this library, you can implement your own entrypoint provider.
• Just tag it with shipmonk.deadCode.entrypointProvider and implement ShipMonk\PHPStan\DeadCode\Provider\MethodEntrypointProvider
• You can simplify your implementation by extending ShipMonk\PHPStan\DeadCode\Provider\SimpleMethodEntrypointProvider

# phpstan.neon.dist
services:
    -
        class: App\ApiOutputEntrypointProvider
        tags:
            - shipmonk.deadCode.entrypointProvider

use ReflectionMethod;
use ShipMonk\PHPStan\DeadCode\Provider\SimpleMethodEntrypointProvider;

class ApiOutputEntrypointProvider extends SimpleMethodEntrypointProvider
{

    public function isEntrypointMethod(ReflectionMethod $method): bool
    {
        return $method->getDeclaringClass()->implementsInterface(ApiOutput::class));
    }
}

Dead cycles & transitively dead methods

• This library automatically detects dead cycles and transitively dead methods (methods that are only called from dead methods)
• By default, it reports only the first dead method in the subtree and the rest as a tip:

 ------ ------------------------------------------------------------------------
  Line   src/App/Facade/UserFacade.php
 ------ ------------------------------------------------------------------------
  26     Unused App\Facade\UserFacade::updateUserAddress
         🪪  shipmonk.deadMethod
         💡 Thus App\Entity\User::updateAddress is transitively also unused
         💡 Thus App\Entity\Address::setPostalCode is transitively also unused
         💡 Thus App\Entity\Address::setCountry is transitively also unused
         💡 Thus App\Entity\Address::setStreet is transitively also unused
         💡 Thus App\Entity\Address::setZip is transitively also unused
 ------ ------------------------------------------------------------------------

• If you want to report all dead methods individually, you can enable it in your phpstan.neon.dist:

parameters:
    shipmonkDeadCode:
        reportTransitivelyDeadMethodAsSeparateError: true

Automatic removal of dead code

• If you are sure that the reported methods are dead, you can automatically remove them by running PHPStan with removeDeadCode error format:

vendor/bin/phpstan analyse --error-format removeDeadCode

class UserFacade
{
-    public function deadMethod(): void
-    {
-    }
}

Calls over unknown types

• In order to prevent false positives, we support even calls over unknown types (e.g. $unknown->method()) by marking all methods named method as used
  • Such behaviour might not be desired for strictly typed codebases, because e.g. single new $unknown() will mark all constructors as used
  • Thus, you can disable this feature in your phpstan.neon.dist:

parameters:
    shipmonkDeadCode:
        trackCallsOnMixed: false

• If you want to check how many of those cases are present in your codebase, you can run PHPStan analysis with -vvv and you will see some diagnostics:

Found 2 methods called over unknown type:
 • setCountry, for example in App\Entity\User::updateAddress
 • setStreet, for example in App\Entity\User::updateAddress

Comparison with tomasvotruba/unused-public

• You can see detailed comparison PR
• Basically, their analysis is less precise and less flexible. Mainly:
  • It cannot detect dead constructors
  • It does not properly detect calls within inheritance hierarchy
  • It does not offer any custom adjustments of used methods
  • It has almost no built-it library extensions
  • It ignores trait methods
  • Is lacks many minor features like class-string calls, dynamic method calls, array callbacks, nullsafe call chains etc
  • It cannot detect dead cycles nor transitively dead methods
  • It has no built-in dead code removal

Limitations:

• Methods of anonymous classes are never reported as dead (PHPStan limitation)
• Abstract trait methods are never reported as dead
• Most magic methods (e.g. __get, __set etc) are never reported as dead
  • Only supported are: __construct, __clone

Other problematic cases:

Constructors:

• For symfony apps & PHPStan extensions, we simplify the detection by assuming all DIC classes have used constructor.
• For other apps, you may get false-positives if services are created magically.
  • To avoid those, you can easily disable consructor analysis with single ignore:

parameters:
    ignoreErrors:
        - '#^Unused .*?::__construct$#'

Private constructors:

• Those are never reported as dead as those are often used to deny class instantiation

Interface methods:

• If you never call interface method over the interface, but only over its implementors, it gets reported as dead
• But you may want to keep the interface method to force some unification across implementors
  • The easiest way to ignore it is via custom MethodEntrypointProvider:

class IgnoreDeadInterfaceMethodsProvider extends SimpleMethodEntrypointProvider
{
    public function isEntrypointMethod(ReflectionMethod $method): bool
    {
        return $method->getDeclaringClass()->isInterface();
    }
}

Future scope:

• Dead class constant detection
• Dead class property detection
• Dead class detection

Contributing

• Check your code by composer check
• Autofix coding-style by composer fix:cs
• All functionality must be tested

Supported PHP versions

• PHP 7.4 - 8.4