Allow null for query parameters in Kotlin panache

[LarsSven]

Quarkus Panache has Kotlin specific extensions that should be used for Kotlin projects when working with Hibernate and Panache. We recently wanted to migrate our Kotlin project from using the Java panache extensions to the Kotlin panache extensions, however it turned out that they behaved differently.

The big difference is that since Kotlin is non-nullable by default, function signatures such as vararg params: Any in Kotlin are different from A java version like vararg params: Object, since an Object is nullable but Any is not. This is a problem, because the query can absolutely take nullable parameters.

For example, the following code would work with the Java version, but not the Kotlin version, since all 3 parameters are possibly null within this context:

find("""
    (cast(?1 AS uuid) IS null OR assignment.courseInstanceId = ?1) AND
    (cast(?2 AS uuid) IS null OR groupId                     = ?2) AND 
    (cast(?3 AS uuid) IS null OR assignment.id               = ?3)
""", courseInstanceId, groupId, assignmentId)

It is also unreasonable to expect the user to deal with nullability outside of the query, as checking for nullability outside of this query makes the query extremely ugly as you'd need to dynamically construct the query based on whether a parameter is null or not.

This PR converts the Any parameter type to Any?, to allow for nullable parameters when using the Kotlin extensions (which is absolutely valid for queries), and to bring the Kotlin version in line with the Java version. These changes are made for both the Kotlin Panache for Hibernate ORM extension as well as the Kotlin Panache for Hibernate Reactive extension.

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[geoand]

Thanks for this!

Sounds reasonable to me, do you agree @yrodiere ?

[yrodiere]

Sounds reasonable to me, do you agree @yrodiere ?

Agreed, this makes sense.

FWIW we've started using @Nullable annotations in Hibernate ORM. It's not for all packages, and I don't know if we did it for the relevant packages (org.hibernate.query I guess?), but if we did, that can help us determine nullability on the Kotlin side.