[Bug]: In Quarkus, build-time injection failure for unused beans from a2asdk libraries

[hakdogan]

What happened?

I’m not sure if it’s because it wasn’t the right place, but I didn’t get a response to the issue I opened in a2a-samples. Unless I’m misjudging, the issue seems like a bug to me, which is why I wanted to share it again here.

PS: The situation I mentioned also applies to the a2a-java-reference-server artifact.

Relevant log output

[ERROR] Failed to execute goal io.quarkus:quarkus-maven-plugin:3.22.3:build (default) on project weather: Failed to build quarkus application: io.quarkus.builder.BuildException: Build failure: Build failed due to errors
[ERROR]         [error]: Build step io.quarkus.arc.deployment.ArcProcessor#validate threw an exception: jakarta.enterprise.inject.spi.DeploymentException: Found 2 deployment problems: 
[ERROR] [1] Unsatisfied dependency for type io.a2a.spec.AgentCard and qualifiers [@PublicAgentCard]
[ERROR]         - injection target: parameter 'agentCard' of io.a2a.server.requesthandlers.JSONRPCHandler constructor
[ERROR]         - declared on CLASS bean [types=[io.a2a.server.requesthandlers.JSONRPCHandler, java.lang.Object], qualifiers=[@Default, @Any], target=io.a2a.server.requesthandlers.JSONRPCHandler]
[ERROR]         The following classes match by type, but have been skipped during discovery:
[ERROR]         - io.a2a.spec.AgentCard has no bean defining annotation (scope, stereotype, etc.)
[ERROR] 
[ERROR] 
[ERROR] [2] Unsatisfied dependency for type io.a2a.server.agentexecution.AgentExecutor and qualifiers [@Default]
[ERROR]         - injection target: parameter 'agentExecutor' of io.a2a.server.requesthandlers.DefaultRequestHandler constructor
[ERROR]         - declared on CLASS bean [types=[io.a2a.server.requesthandlers.DefaultRequestHandler, java.lang.Object, io.a2a.server.requesthandlers.RequestHandler], qualifiers=[@Default, @Any], target=io.a2a.server.requesthandlers.DefaultRequestHandler]
[ERROR]         at io.quarkus.arc.processor.BeanDeployment.processErrors(BeanDeployment.java:1589)
[ERROR]         at io.quarkus.arc.processor.BeanDeployment.init(BeanDeployment.java:338)
[ERROR]         at io.quarkus.arc.processor.BeanProcessor.initialize(BeanProcessor.java:178)
[ERROR]         at io.quarkus.arc.deployment.ArcProcessor.validate(ArcProcessor.java:488)
[ERROR]         at java.base/java.lang.invoke.MethodHandle.invokeWithArguments(MethodHandle.java:733)
[ERROR]         at io.quarkus.deployment.ExtensionLoader$3.execute(ExtensionLoader.java:856)
[ERROR]         at io.quarkus.builder.BuildContext.run(BuildContext.java:255)
[ERROR]         at org.jboss.threads.ContextHandler$1.runWith(ContextHandler.java:18)
[ERROR]         at org.jboss.threads.EnhancedQueueExecutor$Task.doRunWith(EnhancedQueueExecutor.java:2675)
[ERROR]         at org.jboss.threads.EnhancedQueueExecutor$Task.run(EnhancedQueueExecutor.java:2654)
[ERROR]         at org.jboss.threads.EnhancedQueueExecutor.runThreadBody(EnhancedQueueExecutor.java:1627)
[ERROR]         at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.run(EnhancedQueueExecutor.java:1594)
[ERROR]         at java.base/java.lang.Thread.run(Thread.java:1570)
[ERROR]         at org.jboss.threads.JBossThread.run(JBossThread.java:499)
[ERROR]         Suppressed: jakarta.enterprise.inject.UnsatisfiedResolutionException: Unsatisfied dependency for type io.a2a.spec.AgentCard and qualifiers [@PublicAgentCard]
[ERROR]         - injection target: parameter 'agentCard' of io.a2a.server.requesthandlers.JSONRPCHandler constructor
[ERROR]         - declared on CLASS bean [types=[io.a2a.server.requesthandlers.JSONRPCHandler, java.lang.Object], qualifiers=[@Default, @Any], target=io.a2a.server.requesthandlers.JSONRPCHandler]
[ERROR]         The following classes match by type, but have been skipped during discovery:
[ERROR]         - io.a2a.spec.AgentCard has no bean defining annotation (scope, stereotype, etc.)
[ERROR] 
[ERROR] 
[ERROR]                 at io.quarkus.arc.processor.Beans.resolveInjectionPoint(Beans.java:547)
[ERROR]                 at io.quarkus.arc.processor.BeanInfo.init(BeanInfo.java:689)
[ERROR]                 at io.quarkus.arc.processor.BeanDeployment.init(BeanDeployment.java:323)
[ERROR]                 ... 12 more
[ERROR]         Suppressed: jakarta.enterprise.inject.UnsatisfiedResolutionException: Unsatisfied dependency for type io.a2a.server.agentexecution.AgentExecutor and qualifiers [@Default]
[ERROR]         - injection target: parameter 'agentExecutor' of io.a2a.server.requesthandlers.DefaultRequestHandler constructor
[ERROR]         - declared on CLASS bean [types=[io.a2a.server.requesthandlers.DefaultRequestHandler, java.lang.Object, io.a2a.server.requesthandlers.RequestHandler], qualifiers=[@Default, @Any], target=io.a2a.server.requesthandlers.DefaultRequestHandler]
[ERROR]                 at io.quarkus.arc.processor.Beans.resolveInjectionPoint(Beans.java:547)
[ERROR]                 at io.quarkus.arc.processor.BeanInfo.init(BeanInfo.java:689)
[ERROR]                 at io.quarkus.arc.processor.BeanDeployment.init(BeanDeployment.java:323)
[ERROR]                 ... 12 more

Code of Conduct

• I agree to follow this project's Code of Conduct

[kabir]

If you want to use the reference implementation and the quarkus-maven-plugin to build a server you will need to provide the AgentCard and AgentExecutor yourself, since that is where the integration with your stuff takes place.

For our TCK we do that here: https://github.com/a2aproject/a2a-java/tree/main/tck/src/main/java/io/a2a/tck/server
For the reference implementation test, we use these https://github.com/a2aproject/a2a-java/tree/main/tests/server-common/src/test/java/io/a2a/server/apps/common.

I presume the samples also provide instances of these classes

[hakdogan]

If you want to use the reference implementation

Hi @kabir

This is exactly the point I want to argue. Having a dependency shouldn't be a sufficient reason to generate a compile-time error when there are no references to the dependency's classes in the application.

[kabir]

I don't think it is a compile error. Rather it is Quarkus trying to build a server and not finding those beans.

If you remove the quarkus-maven-plugin from your project it should work fine. If you want to use quarkus-maven-plugin to create a server, you need to provide those CDI beans.

I may well be misunderstanding what you are trying to do. What I say is my takeaways from fighting with this stuff last week in #211.

[hakdogan]

If you remove the quarkus-maven-plugin from your project it should work fine.

While in the development phase and using Maven, I can't find a reasonable justification for not using the Maven plugin.

I may well be misunderstanding what you are trying to do.

In fact, I'm not trying to test anything.

I'm simply trying to understand the current behavior. When I add any extension as a dependency in Quarkus, as long as I don't reference it explicitly in the code, I don't get a CDI resolution error. However, when I have a2a-java-reference-server dependency, even though I haven't explicitly attempted to create an AgentCard in the code, Quarkus tries to inject a non-existent AgentCard into the JSONRPCHandler at compile time.

This suggests a design decision where having the dependency implies that an implementation is mandatory.

I consider this behavior overly strict and a significant limitation, and I'm only trying to discover whether there's a meaningful reason behind it.

[kabir]

Are you able to share your POM?

But if you don't want to build Quarkus and get CDI errors, then remove the build goal from the plugin. That is what is failing:

[ERROR] Failed to execute goal io.quarkus:quarkus-maven-plugin:3.22.3:build (default) on project weather: Failed to build quarkus application: io.quarkus.builder.BuildException: Build failure: Build failed due to errors

The actual compiler step should work fine, and looks like this example, and happens before

[INFO] --- compiler:3.11.0:compile (default-compile) @ a2a-java-sdk-tests-server-common ---
[INFO] No sources to compile

[hakdogan]

I'm not sure if I was able to convey what I see as a problem, or whether you don't consider what I see as a problem to be a problem. If I add the a2a-java-reference-server dependency to any Quarkus project (and do nothing else), I get an unsatisfied dependency error — and I don't think this behavior is correct. To reproduce the behavior I find problematic, you can simply add the a2a-java-reference-server dependency to a Quarkus project, or follow the steps I described here related to the weather_agent project.

To reiterate, I find it quite restrictive that having the a2a-java-reference-server dependency mandates producing an AgentCard and AgentExecuter, and that to avoid this requirement, one would have to remove either the Maven plugin (which provides most of Quarkus's core functionality) or its build goal—effectively disabling at least the conditional usage scenario.

[kabir]

Hi,

I am not a Quarkus expert by any means (I work on WildFly in my main job). So my understanding might be not be perfect.

But IMHO what you are seeing is the expected behaviour. The way I see it is that "Creating a Quarkus" project, means you have something that should deploy/run in Quarkus. The absence of any beans for the AgentExecutor and AgentCard means the application is not complete, and thus can't run.

Now, I realise you are talking about building it and you are not concerned about running it yet. You would get those errors when running it though, but perhaps you mean you don't want errors at build time before you have got around to adding those classes.

I'm not sure how we would do that apart from changing all injection points of AgentCard from
@PublicAgentCard AgentCard agentCard to something like @PublicAgentCard Instance<AgentCard> agentCard (and then doing agentCard.get()) which seems too intrusive since those are everywhere. Also, we'd need to do the same for AgentExecutor.

I'll see if I can find someone from the Quarkus team knows the best practice around this.

[kabir]

Hi @hakdogan

I got some feedback, and it seems this is a bit of a grey zone, and both our takes on this are valid.

However, I did get a suggested workaround which I have done in #215. Does that meet your needs?

We'll need to see what the others think too before it can be merged.

[hakdogan]

Hi @kabir

Does that meet your needs?

In the Quarkus application context, providing default, non-functional AgentCard and AgentExecutor beans resolves the issue I'm addressing.

[hakdogan]

Hi @kabir

When I learned that the new A2A Java SDK version was released today, I first updated the dependency in my example and then checked whether the issue we discussed here still occurred. At compile time, I got the UnsatisfiedResolutionException error, which seemed to have been suppressed in my first post.

From the first post, the previous case

Suppressed: jakarta.enterprise.inject.UnsatisfiedResolutionException: Unsatisfied dependency for type io.a2a.spec.AgentCard and qualifiers [@PublicAgentCard]
[ERROR]         - injection target: parameter 'agentCard' of io.a2a.server.requesthandlers.JSONRPCHandler constructor
[ERROR]         - declared on CLASS bean [types=[io.a2a.server.requesthandlers.JSONRPCHandler, java.lang.Object], qualifiers=[@Default, @Any], target=io.a2a.server.requesthandlers.JSONRPCHandler]
[ERROR]         The following classes match by type, but have been skipped during discovery:
[ERROR]         - io.a2a.spec.AgentCard has no bean defining annotation (scope, stereotype, etc.)

After upgrading to version 0.3.0.Alpha1, the new case

[ERROR] Failed to execute goal io.quarkus.platform:quarkus-maven-plugin:3.24.3:build (default) on project financial-agent: Failed to build quarkus application: io.quarkus.builder.BuildException: Build failure: Build failed due to errors
[ERROR]         [error]: Build step io.quarkus.arc.deployment.ArcProcessor#validate threw an exception: jakarta.enterprise.inject.spi.DeploymentException: jakarta.enterprise.inject.UnsatisfiedResolutionException: Unsatisfied dependency for type io.a2a.server.agentexecution.AgentExecutor and qualifiers [@Default]
[ERROR]         - injection target: parameter 'agentExecutor' of io.a2a.server.requesthandlers.DefaultRequestHandler constructor
[ERROR]         - declared on CLASS bean [types=[io.a2a.server.requesthandlers.DefaultRequestHandler, java.lang.Object, io.a2a.server.requesthandlers.RequestHandler], qualifiers=[@Default, @Any], target=io.a2a.server.requesthandlers.DefaultRequestHandler]
[ERROR]         at io.quarkus.arc.processor.BeanDeployment.processErrors(BeanDeployment.java:1594)
[ERROR]         at io.quarkus.arc.processor.BeanDeployment.init(BeanDeployment.java:341)
[ERROR]         at io.quarkus.arc.processor.BeanProcessor.initialize(BeanProcessor.java:178)
[ERROR]         at io.quarkus.arc.deployment.ArcProcessor.validate(ArcProcessor.java:488)
[ERROR]         at java.base/java.lang.invoke.MethodHandle.invokeWithArguments(MethodHandle.java:733)
[ERROR]         at io.quarkus.deployment.ExtensionLoader$3.execute(ExtensionLoader.java:856)
[ERROR]         at io.quarkus.builder.BuildContext.run(BuildContext.java:255)
[ERROR]         at org.jboss.threads.ContextHandler$1.runWith(ContextHandler.java:18)
[ERROR]         at org.jboss.threads.EnhancedQueueExecutor$Task.doRunWith(EnhancedQueueExecutor.java:2651)
[ERROR]         at org.jboss.threads.EnhancedQueueExecutor$Task.run(EnhancedQueueExecutor.java:2630)
[ERROR]         at org.jboss.threads.EnhancedQueueExecutor.runThreadBody(EnhancedQueueExecutor.java:1622)
[ERROR]         at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.run(EnhancedQueueExecutor.java:1589)
[ERROR]         at java.base/java.lang.Thread.run(Thread.java:1570)
[ERROR]         at org.jboss.threads.JBossThread.run(JBossThread.java:501)
[ERROR] Caused by: jakarta.enterprise.inject.UnsatisfiedResolutionException: Unsatisfied dependency for type io.a2a.server.agentexecution.AgentExecutor and qualifiers [@Default]
[ERROR]         - injection target: parameter 'agentExecutor' of io.a2a.server.requesthandlers.DefaultRequestHandler constructor
[ERROR]         - declared on CLASS bean [types=[io.a2a.server.requesthandlers.DefaultRequestHandler, java.lang.Object, io.a2a.server.requesthandlers.RequestHandler], qualifiers=[@Default, @Any], target=io.a2a.server.requesthandlers.DefaultRequestHandler]
[ERROR]         at io.quarkus.arc.processor.Beans.resolveInjectionPoint(Beans.java:547)
[ERROR]         at io.quarkus.arc.processor.BeanInfo.init(BeanInfo.java:689)
[ERROR]         at io.quarkus.arc.processor.BeanDeployment.init(BeanDeployment.java:326)
[ERROR]         ... 12 more