NPEs when using @ParameterGroup with custom Pageable and adding descriptions to fields

[arjunchhabra-invitae]

Describe the bug

• When using a custom class that extends from Pageable and receiving it with @ParameterGroup at an endpoint, if you attempt to annotate a field with a description within that class, you will receive an NPE when accessing the generated docs and return a 500.
• If you use this same class as a @ParameterGroup but remove the reference to Pageable, the docs are generated correctly and the descriptions are displaye.

To Reproduce
Steps to reproduce the behavior:

• What version of spring-boot you are using? 2.5.5
• What modules and versions of springdoc-openapi are you using? 1.5.12
• What is the actual and the expected result using OpenAPI Description (yml or json)? Expect actual yml/json generation, but receive a 500
• Provide with a sample code (HelloController) or Test that reproduces the problem

in Controller.kt...

    @GetMapping
    fun getSomething(@ParameterObject example: ExampleClass) {

in ExampleClass.kt...

data class ExampleClass (
    @field:Parameter(description = "Anything")
    val something: Int = 0
) : Pageable {

    override fun getPageNumber(): Int {
        TODO("Not yet implemented")
    }

    override fun getPageSize(): Int {
        TODO("Not yet implemented")
    }

    override fun getOffset(): Long {
        TODO("Not yet implemented")
    }

    override fun getSort(): Sort {
        TODO("Not yet implemented")
    }

    override fun next(): Pageable {
        TODO("Not yet implemented")
    }

    override fun previousOrFirst(): Pageable {
        TODO("Not yet implemented")
    }

    override fun first(): Pageable {
        TODO("Not yet implemented")
    }

    override fun withPage(pageNumber: Int): Pageable {
        TODO("Not yet implemented")
    }

    override fun hasPrevious(): Boolean {
        TODO("Not yet implemented")
    }
}

in ExampleClass2.kt...

data class ExampleClass2 (
    @field:Parameter(description = "Anything")
    val something: Int = 0
)

The above will fail with 500. If you replace ExampleClass with ExampleClass2 in Controller.kt, the docs will generate and include the description.

[bnasslahsen]

@arjun-chhabra,

Not reproducible.
Make sure you provide a minimal reproducible simple as described in the contribution guide.
This ticket will be closed and can be reopened if the relevant information are provided.

[arjunchhabra-invitae]

@bnasslahsen

Here is a self contained reproducer project.

exampleProject.zip

If you stand up the server with ./gradlew bootRun and access the docs, you should receive an NPE and a HTTP500.

If you replace ExamplePageable with ExampleNonPageable in ExampleController, the issue will resolve and the docs will be generated as expected.

Thank you again for your attention into this matter and my apologies if I am simply misconfiguring something.

[bnasslahsen]

@arjun-chhabra,

This will be fixed with the next release.
You can already validate the fix, using the latest SNAPSHOT.

[arjunchhabra-invitae]

Thank you for the quick turnaround on this @bnasslahsen! Much appreciated!