Allow entities in quarkus-mongodb-panache-kotlin to use data class with val

[loriepisicchio]

Description

I have a project using mongodb-panache-kotlin extension to manipulate data in a MongoDB. We follow the repository pattern as presented in the documentation, using Kotlin data classes.

The documentation found here states that the Kotlin data classes representing Mongo Entities can use either val or var for the properties.

But I noticed that when using val, the Mongo driver returns an object with null values for every properties.

I have a project to reproduce the issue here : https://github.com/loriepisicchio/mongo-panache-kotlin

You can run UserMedicalStudyPanacheRepositoryTest as integration test. You will see the tests failing because the object properties are null.
If you change vals into var in UserMedicalStudyEntity, the tests will pass.

Let me know if you need more information.

Implementation ideas

No response

[quarkus-bot]

/cc @FroMage (panache), @geoand (kotlin), @loicmathieu (mongodb,panache)

[geoand]

Thanks a lot for reporting this!

I'll say right off the bat that I find it unlikely that Quarkus can do much here, however it's very hard to tell because the example application does not merely use Quarkus and Mongo, but it also seems to have some kind of DTO mapping layer.

Have you tried checking a simplified version where Mongo Panache is used directly?

[loriepisicchio]

@geoand I have added a new commit in the repository to remove shapeShift mapping. As you will see, tests are still failing if I use the Entity directly without any additional mapping step.

[geoand]

This seems to be a limitation in the Mongo driver. There does seem to be a Kotlin driver as well, but I haven't tried

[loriepisicchio]

@geoand not sure I understand your answer. I am using io.quarkus:quarkus-mongodb-panache-kotlin if that's what you were referring to (see https://github.com/loriepisicchio/mongo-panache-kotlin/blob/main/build.gradle.kts#L43)

My point is : if this is not possible to use val, then the documentation page should be explicit about this limitation. In the current page, we have this

[geoand]

Right, my point is that it's probably possible to improve on this, but it's not something Quarkus does anything about (it's the Mongo driver that handles it) at this point.

[kuoche1712003]

I think the documentation means:
If you use the @BsonCreator approach, you can use either 'val' or 'var'.
However, the no-arg plugin approach only supports 'var'.