feign-kotlin: Decoder type returns "Object" when method is suspending

Description

public interface TestClient  {
    @RequestLine("GET /{uuid}")
    public suspend fun testGet(@Param("uuid") uuid: UUID): TestObject
}

public class CustomDecoder: Decoder {
    override fun decode(response: Response, type: Type): Any? {
        if (response.status() != 404 && response.status() != 204) {
                ...
                println(type)
               ...
            }
        } else {
           ...
        }
    }
}

Contributor guide

Tech stack

kotlinjava

Domain

backendapi

Issue type

bug

DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.

3

Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.

half day

Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.

stale

ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.

mostly clear

Prerequisites

Kotlin coroutinesFeign basicsCustom decoder usage

Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.

40

Research direction

Investigate how Feign resolves the return type for suspend functions in the feign kotlin module. The issue likely stems from the method handler not converting the Continuation generic type to the actual response type. Look at KotlinReflective.FeignInvocationHandler or the DefaultDecoder to see how non suspend methods retrieve Type. Compare with suspend function handling in the same codebase. Consider checking the Kotlin coroutines reflection API to extract the underlying return type.