ViewsBulkOperationsActionBase::executeMultiple() return type fatal

Thank you for reporting, we should deprecate missing return type now and add it in the next major to the API.

Here’s a deprecated return type trait pattern:

namespace Drupal\your_module\Traits;

/**
 * Provides a helper to smoothly transition to strict PHP return types.
 */
trait ReturnTypeDeprecationTrait {

  /**
   * Tracks checked classes and methods to prevent performance-heavy reflection loops.
   *
   * @var array<string, array<string, bool>>
   */
  private static array $checkedReturnTypeSignatures = [];

  /**
   * Triggers a deprecation warning if a child class overrides a method without the proper return type.
   *
   * @param string $methodName
   *   The name of the method to inspect.
   * @param string $expectedType
   *   The expected native return type (e.g., 'array', 'string', 'int', or a FQCN).
   * @param string $version
   *   The future version when this type will become strictly enforced.
   */
  protected function deprecateMissingReturnType(string $methodName, string $expectedType, string $version = '2.0'): void {
    $currentClass = static::class;

    // Fast-return if this specific method on this specific class has already been verified.
    if (isset(self::$checkedReturnTypeSignatures[$currentClass][$methodName])) {
      return;
    }

    // Cache the check immediately so reflection runs exactly once per lifecycle.
    self::$checkedReturnTypeSignatures[$currentClass][$methodName] = true;

    try {
      $reflection = new \ReflectionMethod($this, $methodName);
      
      // Determine the base class where the trait is being used.
      $baseClass = $reflection->getPrototype()->getDeclaringClass()->getName();

      // If the method definition belongs to a child class, check its signature.
      if ($reflection->getDeclaringClass()->getName() !== $baseClass) {
        $returnType = $reflection->getReturnType();

        // Trigger deprecation if there is no type hint, or if it doesn't match the expected type.
        if ($returnType === null || $returnType->getName() !== $expectedType) {
          @trigger_error(
            sprintf(
              'Method "%s::%s()" will require a native "%s" return type declaration in v%s. Please update your child class definition to avoid fatal errors.',
              $currentClass,
              $methodName,
              $expectedType,
              $version
            ),
            E_USER_DEPRECATED
          );
        }
      }
    }
    catch (\ReflectionException $e) {
      // Fail silently if the method doesn't exist to prevent unexpected runtime crashes.
    }
  }

}