Compilation error on using Generics for Rest Client: java.lang.RuntimeException: Invalid type for descriptor T

[ricardoalonso]

Describe the bug

When creating clients for Rest Service, I was trying to create a generic interface to map the methods from PanacheEntityResource class that's used to create services for entities:

@Produces(MediaType.APPLICATION_JSON)
public interface BasicClient<T extends BasicType> {    
    @GET    
    T get();
}

@Path("/typea")
@RegisterRestClient(configKey = "typeab-service")
public interface TypeAClient extends BasicClient<TypeA> {
}

@Path("/typeb")
@RegisterRestClient(configKey = "typeab-service")
public interface TypeBClient extends BasicClient<TypeB> {
}

I have created a simple project ( code-with-quarkus.zip ) to show the problem. The regular Java compilation (without tests) runs fine, but when the client is used, the problem appears:

[ERROR] Errors:
[ERROR]   ServiceTest.testTypeAClient » Runtime java.lang.RuntimeException: io.quarkus.builder.BuildException: Build failure: Build failed due to errors        
[error]: Build step io.quarkus.arc.deployment.ArcProcessor#generateResources threw an exception: java.lang.reflect.UndeclaredThrowableException        
at io.quarkus.deployment.ExtensionLoader$3.execute(ExtensionLoader.java:860)        
at io.quarkus.builder.BuildContext.run(BuildContext.java:256)        
at org.jboss.threads.ContextHandler$1.runWith(ContextHandler.java:18)        
at org.jboss.threads.EnhancedQueueExecutor$Task.doRunWith(EnhancedQueueExecutor.java:2516)        
at org.jboss.threads.EnhancedQueueExecutor$Task.run(EnhancedQueueExecutor.java:2495)        
at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.run(EnhancedQueueExecutor.java:1521)        
at java.base/java.lang.Thread.run(Thread.java:1583)        
at org.jboss.threads.JBossThread.run(JBossThread.java:483)
Caused by: java.util.concurrent.ExecutionException: java.lang.RuntimeException: Invalid type for descriptor T        
at java.base/java.util.concurrent.FutureTask.report(FutureTask.java:122)        
at java.base/java.util.concurrent.FutureTask.get(FutureTask.java:191)        
at io.quarkus.arc.processor.BeanProcessor.generateResources(BeanProcessor.java:432)        
at io.quarkus.arc.deployment.ArcProcessor.generateResources(ArcProcessor.java:537)        
at java.base/java.lang.invoke.MethodHandle.invokeWithArguments(MethodHandle.java:733)        
at io.quarkus.deployment.ExtensionLoader$3.execute(ExtensionLoader.java:854)        
... 7 more
Caused by: java.lang.RuntimeException: Invalid type for descriptor T        
at io.quarkus.gizmo.DescriptorUtils.typeToString(DescriptorUtils.java:222)        
at io.quarkus.gizmo.MethodDescriptor.<init>(MethodDescriptor.java:66)        
at io.quarkus.gizmo.MethodDescriptor.of(MethodDescriptor.java:109)        
at io.quarkus.arc.processor.ClientProxyGenerator.generate(ClientProxyGenerator.java:161)        
at io.quarkus.arc.processor.BeanProcessor$4$1.call(BeanProcessor.java:326)        
at io.quarkus.arc.processor.BeanProcessor$4$1.call(BeanProcessor.java:323)        
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:317)        
... 6 more

If I implement without the interface, it works fine.

Expected behavior

Use a generic super interface to map common methods.

Actual behavior

See the above stack trace.

How to Reproduce?

See the attached sample project.

Output of uname -a or ver

Linux localhost.localdomain 6.9.12-200.fc40.x86_64 #1 SMP PREEMPT_DYNAMIC Sat Jul 27 15:56:15 UTC 2024 x86_64 GNU/Linux

Output of java -version

openjdk version "21.0.4" 2024-07-16 OpenJDK Runtime Environment (Red_Hat-21.0.4.0.7-2) (build 21.0.4+7) OpenJDK 64-Bit Server VM (Red_Hat-21.0.4.0.7-2) (build 21.0.4+7, mixed mode, sharing)

Quarkus version or git rev

3.14.1

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

Apache Maven 3.9.8 (36645f6c9b5079805ea5009217e36f2cffd34256)
Maven home: /home/ricardo.alonso/.m2/wrapper/dists/apache-maven-3.9.8-bin/337e6d14/apache-maven-3.9.8
Java version: 21.0.4, vendor: Red Hat, Inc., runtime: /usr/lib/jvm/java-21-openjdk-21.0.4.0.7-2.fc40.x86_64
Default locale: en_GB, platform encoding: UTF-8
OS name: "linux", version: "6.9.12-200.fc40.x86_64", arch: "amd64", family: "unix"

Additional information

No response

[quarkus-bot]

/cc @cescoffier (rest-client), @geoand (rest-client)

[geoand]

This is kind of a weird case to be honest...

I absolutely understand what you are trying to do, but currently there is no way to tell Quarkus to not make BasicClient a REST Client interface itself.

Perhaps we could introduce something like @IgnoreForRestClient

[ricardoalonso]

Let me understand. Quarkus try to create the Rest Client proxy from the child interface which is annotated and from the father interface, which is not annotated?

[geoand]

It tries to create them for all the interfaces in your case

[ricardoalonso]

The @IgnoreForRestClient could be a solution, but could be simpler to just not follow the hierarchy tree? Only generate the client proxy for the explicit annotated interface and not for the relatives?

[geoand]

Unfortunately that would not work because it's perfectly valid to have non annotated interfaces for the rest client

[gsmet]

Is it mandated? Because I can see how it could be impractical in the end.

Being explicit about when you want a client doesn’t seem too far fetched?

Also in this very case, maybe we should just skip it? It’s not annotated and it’s invalid, looks like something we could skip?

[geoand]

Is it mandated?

Yes, otherwise the programmatic usage won't work

It’s not annotated and it’s invalid, looks like something we could skip?

Invalid how? You mean because of the generics?

[gsmet]

Yeah, I mean if we know we cannot instantiate it, we might as well skip it.

[geoand]

Potentially, but there could be corner cases

[rekt-hard]

We also just stumbled upon this issue. This was working before we updated our dependencies from quarkus-resteasy* to quarkus-rest*.