Resteasy Reactive detects multiple writers, but only one response type is present

[Postremus]

Describe the bug
I have a GET method annotated with @Produces(MediaType.APPLICATION_JSON).
In the Score Console it says however that I have 2 writers for this method:

[io.quarkus.resteasy.reactive.jackson.runtime.serialisers.JacksonMessageBodyWriter@5a21df38, 
org.jboss.resteasy.reactive.server.providers.serialisers.ServerStringMessageBodyHandler@7a97f70c]

This negativly affects the score of this method. See screenshot.

Expected behavior
RR should not detect a simple Produces(MediaType.APPLICATION_JSON) as multiple writers.

To Reproduce

Steps to reproduce the behavior:

1. Download the reproducer
2. mvn quarkus:dev
3. Go to http://localhost:8080/q/dev/io.quarkus.quarkus-resteasy-reactive/scores

Screenshots

Environment (please complete the following information):

• Output of uname -a or ver:
  Linux martin 5.8.0-41-generic Add proper logging #46~20.04.1-Ubuntu SMP Mon Jan 18 17:52:23 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux
• Output of java -version:
  openjdk 11.0.7 2020-04-14 LTS
  OpenJDK Runtime Environment Zulu11.39+15-CA (build 11.0.7+10-LTS)
  OpenJDK 64-Bit Server VM Zulu11.39+15-CA (build 11.0.7+10-LTS, mixed mode)
• Quarkus version or git rev:
  1.11.1.Final
• Build tool (ie. output of mvnw --version or gradlew --version):
  Apache Maven 3.6.3 (cecedd343002696d0abb50b32b541b8a6ba2883f)
  Maven home: /home/martin/.sdkman/candidates/maven/current
  Java version: 11.0.7, vendor: Azul Systems, Inc., runtime: /home/martin/.sdkman/candidates/java/11.0.7-zulu
  Default locale: en_US, platform encoding: UTF-8
  OS name: "linux", version: "5.8.0-41-generic", arch: "amd64", family: "unix"

[ghost]

/cc @FroMage, @geoand, @stuartwdouglas

[geoand]

Does the GET method return String or something else?

[Postremus]

@geoand yes, indeed it does in this example.
But I have also noticed this behavior when the GET returned a POJO.

[geoand]

Understood. I'll check it out soon

[kwakiutlCS]

I believe this regressed in 1.13.1.Final (same in 1.13.2.Final). In 1.13.0.Final it was ok.

[geoand]

I'll take a look tomorrow

[kwakiutlCS]

I created a small reproducer explaining what I did because I think this is for jackson only, with jsonb works good
https://github.com/kwakiutlCS/reactive-scores

[geoand]

Thanks

[geoand]

#16578 should fix the issue

[kwakiutlCS]

thanks @geoand. Can you clarify also if it is supposed for the score showing 0% when returning a Response object, because it says it only finds the writer in runtime?

I was expecting that
return entity;
and
return Response.ok(entity).build();
to be equivalent, but the scores are different. Is there really a performance difference in resteasy-reactive?

[geoand]

Yes, I can confirm that this is the intended behavior.

The problem is that because Response is not a generic type, RESTEasy Reactive can't know what Java type is being used for the payload at build time and therefore needs to resolve the MessageBodyWriter at runtime

[gsmet]

@geoand I wonder if we should introduce a typed version of Response in RESTEasy Reactive with a proper type argument. It wouldn't be as flexible as you would define the type but I think it could work in a lot of cases.

[geoand]

Yes we have thought about it. If I am not mistaken, @FroMage had a branch with that

[FroMage]

Yup. FroMage@bc744d9 But it's really a POC. I think it would make for a good feature, though. And since it's the second time other people than me have mentioned it, it's probably time to open an issue for it: #16718