Missing boundary for MultipartFormDataOutput

[piu130]

Describe the bug

When returning a MultipartFormDataOutput, the MultipartMessageBodyWriter creates a random boundary (generateBoundary()). The boundary is never added to the Content-Type header.
When parsing the MultipartFormDataOutput response in the client it fails, because of the missing boundary.

Expected behavior

The response Content-Type header should look like Content-Type: multipart/form-data; boundary=--c57ab2f8-48ee-45f8-9268-34339e01cb2b when the boundary is --c57ab2f8-48ee-45f8-9268-34339e01cb2b.

Actual behavior

The response Content-Type header looks like Content-Type: multipart/form-data when the boundary is --c57ab2f8-48ee-45f8-9268-34339e01cb2b.

How to Reproduce?

No response

Output of uname -a or ver

No response

Output of java -version

17.0.5

GraalVM version (if different from Java)

No response

Quarkus version or git rev

2.14.0

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

No response

Additional information

No response

[geoand]

Can provide a sample application that behaves the way you mention?

[piu130]

Hi @geoand , just found out that there are some missing details while creating the example.
I use quarkus-resteasy-reactive. It happens only with RestResponse, while using Response works as expected.
You can find the example here.
I only changed the GreetingResource and its test and removed the integration test from a new reactive project.

@Path("/hello")
public class GreetingResource {

    @GET
    @Produces(MediaType.MULTIPART_FORM_DATA)
    public RestResponse<MultipartFormDataOutput> hello() {
        var res = new MultipartFormDataOutput();
        res.addFormData("key", "entity", MediaType.TEXT_PLAIN_TYPE);
        return RestResponse.ok(res);
    }
}

[geoand]

Thanks for the reproducer. #29799 fixes the issue