Allow type inference from validation

[dresslerdemos]

Currently Symfony Validation is used to validate request data, however, phpstan is not able to infer the type from that, which increases the chance for type based bugs in the code.

Something like https://github.com/jbboehr/phpstan-laravel-validation is needed, but with a license that allows usage inside a MIT (Expat) licensed project, which is not the case with AGPL v3+.

[dresslerdemos]

phpixie/validate: type awareness doesn't seem to be build in; no phpstan compatibility was found

[dresslerdemos]

beberlei/assert: has a phpstan extension, but is (for performance reasons) kept very simple. Thus it is more an alternative to webmozart/assert (which is already used with a phpstan extension) than to Symfony Validation.

[dresslerdemos]

zendframework/zend-validator: is no longer maintained and recommends laminas/laminas-validator

[dresslerdemos]

laminas/laminas-validator: an phpstan extension https://github.com/Slamdunk/phpstan-laminas-framework for the Laminas framework in general, but it does not support the wanted validation typing

[dresslerdemos]

Respect/Validation: no phpstan extension was found

[joorei]

It is quite possible that no library exists that covers all requirements. Also, there is no major concern in keeping Symfony Validation:

• The drawback of missing built-in phpstan support can be mitigated by hard-coding type hints for the logic after the validation as is already done in at least one validator implementations.
• Depending on a component from a large framework may be problematic in case an application needs to use a different version than the one supported by this library. However, Symfony Validation is not the only Symfony component used and trying to keep this library working without any Symfony components will not be done without a specific use case.

Due to those considerations, the investigation is closed for now.