Any chance you could prepare a small Maven reproducer?

It looks legit but it's the kind of thing we can struggle to reproduce.

Thanks!

/cc @FroMage (rest), @geoand (rest)

Somehow, something is wrapping what should be a single content type into a List and this is what you see.

That being said, there's something odd because HeaderHelper is a RESTEasy Classic class and shouldn't be used if you are using RESTEasy Reactive.

I think we really need a small reproducer to be able to check what's going on.

@gsmet

Apologies in advance my reproducers are never the most simple, but I think this one is easy to run.

Decompress the folder and run the start.sh script.

• This will start the nodejs server that serves the SVG file.
• It starts quarkus running a jax-rs handler and has a quarkus rest client calling the nodejs server.

Once the servers are up, takes couple of seconds hit the endpoint using the following:

curl -vvv localhost:8080/public/gms-logo.svg

Expect an exception like the one mentioned in the issue above.

bug.zip

OK, so you can workaround it by being a bit more careful when copying the headers and iterate on them if a list is returned but I kinda agree we should do better on our side.

Working on a PR.

OK, so you can workaround it by being a bit more careful when copying the headers and iterate on them if a list is returned but I kinda agree we should do better on our side.

Working on a PR.

The reproducer has that header iteration, but the problem happens before. That iteration was just an experiment I was trying out related to yet another issue.

The reproducer has that header iteration, but the problem happens before. That iteration was just an experiment I was trying out related to yet another issue.

So from what I can see, if I drop the header transformation from your reproducer, things are working fine, even without my patch.

So my PR is fixing the issue in the reproducer but I'm not sure it will fix the issue you have in your app, if you're under the impression it's not these lines failing. It might but I'm not sure.

Also there's something that is problematic in your issue description:

java.lang.ClassCastException: class java.util.Arrays$ArrayList
  cannot be cast to class jakarta.ws.rs.core.MediaType
	at org.jboss.resteasy.util.HeaderHelper.getMediaType(HeaderHelper.java:115)

org.jboss.resteasy.util.HeaderHelper is a class from RESTEasy Classic and AFAICS, you are using Quarkus REST/RESTEasy Reactive so I'm not entirely sure what's going on but it seems you have a mix of both.

I think you should try to understand what's going on there with your dependency tree.

On the positive side, I created a PR here: #47546 .

I would be interested in your feedback. Ideally if could build my PR and test things with your app, that would give us an indication as to if the issue is fixed for you.

https://github.com/quarkusio/quarkus/blob/main/CONTRIBUTING.md#checking-an-issue-is-fixed-in-main might help (except you have to build my PR code instead as long as it's not merged).

The reproducer has that header iteration, but the problem happens before. That iteration was just an experiment I was trying out related to yet another issue.

So from what I can see, if I drop the header transformation from your reproducer, things are working fine, even without my patch.

That's correct, and to clear things out, removing the handling of the headers stops the exception to be thrown. What I meant is the code triggers the exception at a lower level.

So my PR is fixing the issue in the reproducer but I'm not sure it will fix the issue you have in your app, if you're under the impression it's not these lines failing. It might but I'm not sure.

Also there's something that is problematic in your issue description:

java.lang.ClassCastException: class java.util.Arrays$ArrayList
  cannot be cast to class jakarta.ws.rs.core.MediaType
	at org.jboss.resteasy.util.HeaderHelper.getMediaType(HeaderHelper.java:115)

org.jboss.resteasy.util.HeaderHelper is a class from RESTEasy Classic and AFAICS, you are using Quarkus REST/RESTEasy Reactive so I'm not entirely sure what's going on but it seems you have a mix of both.

I think you should try to understand what's going on there with your dependency tree.

Again you are right here, I've cleanup the dependencies and without the headers handling I don't get the original issue (not disclosed) and the exception.

On the positive side, I created a PR here: #47546 .

I would be interested in your feedback. Ideally if could build my PR and test things with your app, that would give us an indication as to if the issue is fixed for you.

I think if there was a need to handle the headers the issue would still be there, so I believe your PR still valid.

https://github.com/quarkusio/quarkus/blob/main/CONTRIBUTING.md#checking-an-issue-is-fixed-in-main might help (except you have to build my PR code instead as long as it's not merged).

Thanks for looking into this, it's really appreciated.