RESTEasy Reactive does not call method ParamConverter#toString for collection elements

[timonzi]

Describe the bug

The fix in #35774 allows the definition of REST resources with a collection of parameterized types as a query parameter.

Example (from #35774):

@GET
@Path("/wrapperList")
public String wrapperList(@QueryParam("wrapperList") final List<WrapperClass<StatusEnum>> wrapperList) {
    // ...
}

The problem what I found now is that toString method of my ParamConverter implementation is not called for the collection elements. Because of this the fromString method gets a class reference as String value (e.g. org.acme.WrapperClass@59e082f8) instead of the expected one.

public class WrapperClassParamConverter implements ParamConverter<WrapperClass<?>> {

  // [...]

    @Override
    public WrapperClass<?> fromString(String value) {
        return new WrapperClass<>(Enum.valueOf(StatusEnum.class, value));
    }

    @Override
    public String toString(WrapperClass<?> wrapperClass) {
        // RESTEasy Reactive: Not called for elements of a collection.
        // RESTEasy Classic: Calls the method for every element
        return wrapperClass != null ? wrapperClass.getValue().toString() : null;
    }

}

So the current implementation works fine when I simply provide a String value when calling the REST resource. This is what I did when testing the fix of #35774.

But when I now use the REST client to call a resource of another service, the toString method should be called to serialize the value and on the other side the fromString method should be called. For the fromString this works fine, but the toString method is never called.

Expected behavior

The toString method from parameter converters should be used like in RESTEasy Classic - so also for collections.

Actual behavior

The toString method is never called for collection elements.

How to Reproduce?

Reproducer: https://github.com/timonzi/resteasy-reactive-wrapper-collection-elements

1. Execute tests in ParametersResourceTest --> testCollectionViaClient will fail (because of the unexpected value in the fromString implementation)
2. Switch to RESTEasy Classic implementation (commented dependencies are already in the pom.xml) --> tests will work

Output of uname -a or ver

Linux nb-timonz 6.2.0-31-generic #31~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Wed Aug 16 13:45:26 UTC 2 x86_64 x86_64 x86_64 GNU/Linux

Output of java -version

OpenJDK Runtime Environment Temurin-17.0.6+10 (build 17.0.6+10)

Quarkus version or git rev

3.2.7.Final

Build tool (ie. output of mvnw --version or gradlew --version)

Apache Maven 3.9.3 (21122926829f1ead511c958d89bd2f672198ae9f)

Additional information

The fix of #35774 is also included in 3.2.7.Final. This version is used in the reproducer.

[quarkus-bot]

/cc @FroMage (resteasy-reactive), @geoand (resteasy-reactive), @stuartwdouglas (resteasy-reactive)

[geoand]

Thanks for reporting.

I'll try and have a look next week

[geoand]

#36885 fixes the issue