Why is injecting a service into an entity considered bad practice?

Question

symfony

Hey!
Why is injecting a service into an entity considered bad practice?
For example UserPasswordEncoderInterface in User->setPassword
or NotBlank validator in User setUsername

Answer 1

It is more correct to say not "bad practice", but "violates SOLID".
"Service in essence" violates the Single Responsibility Principle (SRP) by combining in one object both the representation of the object itself and some external logic.
It doesn't mean it's "bad" or "good"! There are different (sometimes mutually exclusive) approaches, it is not necessary to run into strict adherence to them all. Here is an example where this can greatly complicate development: https://habr.com/ru/post/153225/
UserPasswordEncoderInterface and NotBlank are not services, but validators. They refer to the internal logic of the object, not only do not violate the SRP, but they must be in this object.