Need a way to indicate no additional restrictions

[njr-11]

This came up during discussion of one of the other issues.
Given a repository method that allows Restrictions to be supplied at run time, such as,

@Find
List<Person> bornIn(int year, Restriction<Person> restrictions, Order<Person> order);

There is currently no way for a repository user to use the method when a case arises where they don't need to make any additional restrictions.

Currently, allowing for that possibility would require the repository to duplicate the method and omit the Restriction parameter,

@Find
List<Person> bornIn(int year, Order<Person> order);

One idea to avoid the need to duplicate repository methods is to allow an empty Restriction instance that indicates the decision to not apply any additional restrictions,

everyoneBornIn2000 = people.bornIn(2000, Restrict.none(), Order.by(_Person.ssn.asc()));

I'm not sure what a good name for it is. This PR calls it Restrict.none(), but open to better ideas for names.

[otaviojava]

@njr-11 shall we combine those?

One is for static query, and the other one is for dynamic.

Using your sample:

@Find
List<Person> bornIn(int year, Restriction<Person> restrictions, Order<Person> order);

I could you do the same using:

@Find
List<Person> bornIn(Restriction<Person> restrictions, Order<Person> order);

And implement this way:

Restriction<Person> restriction = _Person.age().in(List.of(1,2,3);

I am inclined to run an exception when the user tries this approach.

[gavinking]

I think Restrict.none() is pretty ambiguous, and could be read as "restrict to none". That's why I called it unrestricted() on the Hibernate API.

[njr-11]

@njr-11 shall we combine those?

One is for static query, and the other one is for dynamic.

Using your sample:

@Find
List<Person> bornIn(int year, Restriction<Person> restrictions, Order<Person> order);

I could you do the same using:

@Find
List<Person> bornIn(Restriction<Person> restrictions, Order<Person> order);

And implement this way:

Restriction<Person> restriction = _Person.age().in(List.of(1,2,3);

I am inclined to run an exception when the user tries this approach.

@otaviojava I think you misunderstood the point. The presence or absence of a statically defined restriction is not important at all here. We could instead give an example that doesn't use int year, and the exact same problem arises regardless.

A repository provides the following,

@Find
List<Person> findAll(Restriction<Person> restrictions, Order<Person> order);

The repository user computes restrictions at run time, and this works great as long as the set of restrictions is non-empty, but as soon as the the scenario arises that nothing should be restricted, the method cannot be used anymore, and the repository author ends up needing to a duplicate method, but without the Restriction<Person> restrictions,

@Find
List<Person> findAll(Order<Person> order);

This is where a way to represent "no restrictions" is useful, so that duplicated methods can be avoided, and the computation at run time doesn't need to be annoyed with whether to invoke one method or another.

[njr-11]

I think Restrict.none() is pretty ambiguous, and could be read as "restrict to none". That's why I called it unrestricted() on the Hibernate API.

Good idea. I renamed it to unrestricted() in 48e2c3a