cannotBeEmpty on arrayNode is deprecated in symfony 3 and removed in 4

[JMLamodiere]

Here is the warning when using symfony 3.4 :

Using Symfony\Component\Config\Definition\Builder\ArrayNodeDefinition::cannotBeEmpty() at path "liip_monitor.mailer.recipient" has no effect, consider requiresAtLeastOneElement() instead. In 4.0 both methods will behave the same.

See symfony source code, it's a @trigger_error in sf3 and an exception in sf4 :

• 3.4 : https://github.com/symfony/config/blob/3.4/Definition/Builder/ArrayNodeDefinition.php#L415
• 4.0 : https://github.com/symfony/config/blob/4.0/Definition/Builder/ArrayNodeDefinition.php#L476

A similar fix can be viewed in another bundle : https://github.com/nelmio/NelmioJsLoggerBundle/pull/20

[kbond]

Thanks @JMLamodiere, I did notice this the other day.