check-dependency-injection

Dependency Injection Check

Analyze PHP code for proper dependency injection patterns.

Detection Patterns

1. New Keyword in Business Logic

// BAD: Hard-coded dependency
class OrderService
{
    public function process(Order $order): void
    {
        $mailer = new Mailer(); // Can't mock this
        $mailer->send($order->getCustomer(), 'confirmation');
    }
}

// GOOD: Injected dependency
class OrderService
{
    public function __construct(
        private MailerInterface $mailer,
    ) {}

    public function process(Order $order): void
    {
        $this->mailer->send($order->getCustomer(), 'confirmation');
    }
}

2. Service Locator Antipattern

// BAD: Service locator
class UserService
{
    public function register(UserData $data): User
    {
        $hasher = Container::get(PasswordHasher::class);
        $repository = Container::get(UserRepository::class);
        $mailer = Container::get(Mailer::class);

        // Dependencies are hidden
    }
}

// GOOD: Constructor injection
class UserService
{
    public function __construct(
        private PasswordHasher $hasher,
        private UserRepository $repository,
        private Mailer $mailer,
    ) {}

    // Dependencies are explicit
}

3. Static Method Calls

// BAD: Static calls can't be mocked
class ReportGenerator
{
    public function generate(): Report
    {
        $data = Database::query('SELECT ...');  // Static
        $date = Carbon::now();                   // Static
        $id = Uuid::uuid4();                     // Static

        return new Report($data, $date, $id);
    }
}

// GOOD: Injectable services
class ReportGenerator
{
    public function __construct(
        private Connection $database,
        private ClockInterface $clock,
        private UuidGenerator $uuidGenerator,
    ) {}

    public function generate(): Report
    {
        $data = $this->database->query('SELECT ...');
        $date = $this->clock->now();
        $id = $this->uuidGenerator->generate();

        return new Report($data, $date, $id);
    }
}