[Symfony2][2.0] A validator which trigger validation constraints only if an entity has some values in its properties. All properties of the entity must have a getter or must be public, otherwise the PropertyPath will throw an exception.

FakeEntity.php

<?php

namespace Sensio\Bundle\FakeBundle\Entity;

use Sensio\Component\Validator\Constraints\ValidateIfNeeded;
use Symfony\Component\Validator\Constraints as Assert;

/**
 * FakeEntity.
 *
 * @ValidateIfNeeded()
 */
class FakeEntity
{
    /**
     * @Assert\NotBlank(groups={"ValidateIfNeeded"})
     */
    public $a;

    /**
     * @Assert\NotBlank(groups={"ValidateIfNeeded"})
     */
    protected $b;

    /**
     * @Assert\NotBlank(groups={"ValidateIfNeeded"})
     */
    private $c;

    public function getB()
    {
        return $this->b;
    }

    public function setB($b)
    {
        $this->b = $b;
    }

    public function getC()
    {
        return $this->c;
    }

    public function setC($c)
    {
        $this->c = $c;
    }
}

services.yml

validator.constraint.validate_if_needed:
    class:      Sensio\Component\Validator\Constraints\ValidateIfNeededValidator
    arguments:  [@validator]
    tags:
        - { name: validator.constraint_validator, alias: validate_if_needed }

ValidateIfNeeded.php

<?php

namespace Sensio\Component\Validator\Constraints;

use Symfony\Component\Validator\Constraint;

/**
 * Constraint for the Validate if needed validator
 *
 * @Annotation
 * @author Pierre-Yves LEBECQ <py.lebecq@gmail.com>
 */
class ValidateIfNeeded extends Constraint
{
    /**
     * {@inheritDoc}
     */
    public function getTargets()
    {
        return self::CLASS_CONSTRAINT;
    }

    /**
     * {@inheritDoc}
     */
    public function validatedBy()
    {
        return 'validate_if_needed';
    }
}

ValidateIfNeededValidator.php

<?php

namespace Sensio\Component\Validator\Constraints;

use Symfony\Component\Validator\ValidatorInterface;
use Symfony\Component\Form\Util\PropertyPath;
use Symfony\Component\Validator\Constraint;
use Symfony\Component\Validator\ConstraintValidator;
use Symfony\Component\Validator\Exception\UnexpectedTypeException;

/**
 * Validates an entity only if it seems to contains some values.
 *
 * @author Pierre-Yves LEBECQ <py.lebecq@gmail.com>
 */
class ValidateIfNeededValidator extends ConstraintValidator
{
    /** @var ValidatorInterface */
    private $validator;

    public function __construct(ValidatorInterface $validator)
    {
        $this->validator = $validator;
    }

    /**
     * {@inheritDoc}
     */
    public function isValid($value, Constraint $constraint)
    {
        if (null === $value) {
            return true;
        }

        if (!is_object($value)) {
            throw new UnexpectedTypeException($value, 'object');
        }

        $hasSomeData        = false;
        $reflectionClass    = new \ReflectionClass($value);
        $properties         = $reflectionClass->getProperties();
        foreach ($properties as $property) {
            $propertyPath   = new PropertyPath($property->getName());
            $propertyValue  = $propertyPath->getValue($value);
            if (null !== $propertyValue) {
                $hasSomeData = true;
            }
        }

        if (!$hasSomeData) {
            return true;
        }

        $walker       = $this->context->getGraphWalker();
        $propertyPath = $this->context->getPropertyPath();
        $metadata     = $this->validator->getMetadataFactory()->getClassMetadata(get_class($value));

        $walker->walkObject($metadata, $value, 'ValidateIfNeeded', $propertyPath);
        $this->context->setPropertyPath($propertyPath); // Reset property path modified by the $walker->walkObject() call

        return true;
    }
}