Can't ignore significant @Id field

[bjansen]

The latest version of equalsverifier complains that our class that extends org.hibernate.envers.DefaultRevisionEntity uses an @Id property as a significant field:

java.lang.AssertionError: EqualsVerifier found a problem in class our.custom.AuditRevision.
-> Significant fields: id is marked @id or @EmbeddedId so equals should not use it, but it does.
Suppress Warning.SURROGATE_KEY if you want to use only the @id or @EmbeddedId field(s).

It seems to me that adding id to the list of ignored fields should make this error disappear, but it does not:

		EqualsVerifier.forClass(AuditRevision.class)
				.suppress(Warning.STRICT_INHERITANCE)
				.withIgnoredFields("id")
				.verify();

In nl.jqno.equalsverifier.internal.checkers.fieldchecks.SignificantFieldCheck#assertFieldShouldNotBeUsed, I see this assertion:

        assertTrue(
            Formatter.of(message, fieldName),
            !fieldShouldBeIgnored ||
            !equalsChanged ||
            skipCertainTestsThatDontMatterWhenValuesAreNull
        );

I'm wondering if the code should read fieldShouldBeIgnored instead of !fieldShouldBeIgnored? I.e. the assertion should pass if the field should be ignored.

[jqno]

EqualsVerifier has recently become a bit more rigorous when it comes to JPA entities. There's a debate on whether it's better to give entities a business key (aka natural key), or a surrogate key. A business key is when all the semantically meaningful fields are part of the object's identity and assumes that the key is just there for technical reasons and doesn't actually mean anything for the user. A surrogate key is when the object's identity relies exclusively on the key, and the actual content of the fields doesn't matter.

EqualsVerifier assumes a business key by default, which means that you can't use id in equals. If you want EqualsVerifier to assume a surrogate key, you can suppress Warning.SURROGATE_KEY (as the error message states!), but then you can only use the id field.

If your class has a business key but the id field actually has a semantic meaning, for instance if you have a Person class and the id field is the person's social security number, you can suppress Warning.SURROGATE_OR_BUSINESS_KEY, which allows you to use both id and other fields in equals.

You can read more about it in the manual: https://jqno.nl/equalsverifier/manual/jpa-entities/

.withIgnoredFields is intended for the opposite use case, where you have a field in your class that you're not using in equals. EqualsVerifier will notice that the field is not used and complain; you can tell EqualsVerifier that that's intended by having it ignored.

[bjansen]

Thanks for the explanation! I read the docs but somehow missed the SURROGATE_OR_BUSINESS_KEY part, which fixed my problem as expected.