id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
37221	Validator equality checks miss unequal configurations	Mike Edmunds	Vishy	"The validator `__eq__()` methods added in #21638 (a68f32579145dfbd51d87e14f9b5e04c770f9081) miss some cases where the validators are ''not'' actually equal. This could lead to missing migrations when changing a field's validators.

== 1. `EmailValidator.__eq__()` does not check its regex attrs

This test should fail, but does not:

{{{#!python
    def test_email_validator_regex_equality(self):
        validate_email_no_idna = EmailValidator()
        validate_email_no_idna.hostname_re = DomainNameValidator.ascii_only_domain_re
        validate_email_no_idna.domain_re = DomainNameValidator.ascii_only_domain_re
        validate_email_no_idna.tld_no_fqdn_re = DomainNameValidator.ascii_only_tld_re

        self.assertNotEqual(validate_email_no_idna, validate_email)
}}}

Compare to the `RegexValidator`-based validators, which ''do'' consider their regex attr for `__eq__()`. (E.g., `DomainNameValidator(accept_idna=True) != DomainNameValidator(accept_idna=False)` correctly, even though `DomainNameValidator` doesn't implement its own `__eq__()` method to check `accept_idna`.)

== 2. No validator `__eq__()` methods check the class

Custom validator subclasses may implement different logic, so should probably ''not'' be considered equal by default. I would expect this test to fail but it does not:

{{{#!python
    def test_custom_domain_name_validator_equality(self):
        class CustomDomainNameValidator(DomainNameValidator):
            def __call__(self, value):
                super().__call__(value)
                if value.lower().endswith(("".info"", "".xyz"", "".biz"")):
                    raise ValidationError(
                        self.message, code=self.code, params={""value"": value}
                    )

        self.assertNotEqual(CustomDomainNameValidator(), DomainNameValidator())
}}}

This ''might'' be considered a programming error that `CustomDomainNameValidator` doesn't override the base `__eq__()` method. But—particularly if we're going to encourage custom subclasses for tweaking validator functionality—it would probably be safer for the base equality check to require the same class. (And subclasses that ''do'' want to claim equality with base could override `__eq__()`.)"	Cleanup/optimization	assigned	Core (Other)	6.0	Normal		validators		Accepted	0	0	0	0	0	0