EmailValidator should use filter_var in strict mode if Egulias library is missing

[ebuildy]

Q	A
Bug report?	no
Feature request?	yes
BC Break report?	no
RFC?	yes/no
Symfony version	4.0.0

Egulias\EmailValidator\EmailValidator is not really perfect (toto@toto.___c is valid whereas it's not for HTML5 or filter_var), so I propose to use filter_var with FILTER_VALIDATE_EMAIL if Egulias is not installed:

EmailValidator:

if (!class_exists('\Egulias\EmailValidator\EmailValidator')) {
                if (filter_var($value, FILTER_VALIDATE_EMAIL) === false) {
                    $this->context->buildViolation($constraint->message)
                        ->setParameter('{{ value }}', $this->formatValue($value))
                        ->setCode(Email::INVALID_FORMAT_ERROR)
                        ->addViolation();

                    return;
                }
            }

[jvasseur]

Having the behavior of the constraint change based on the presence of a dependency looks like a bad idea.

We could add another validation mode that is based on FILTER_VALIDATE_EMAIL but I'm not sure if it's worth it since FILTER_VALIDATE_EMAIL doesn't match any standard (that's why we stopped using it).

[ebuildy]

Yes you are right, I should declare the bug on the library Egulias\EmailValidator instead.

We are using FILTER_VALIDATE_EMAIL in lot of projects, do you have sources saying it's bad?

Thanks you, I am closing the issue so.

[jvasseur]

@ebuildy you can look at the references in the PR that removed the use of filter_var : #9140