Resteasy-reactive produces invalid json for Multi

[fedinskiy]

Describe the bug

While using Multi as a return value for a method annotated with @Produces(MediaType.APPLICATION_JSON), the returned json looks like an array(it uses square brackets around the results), but lacks quotation marks around the strings inside e.g. [Hello,Hola] instead of ["Hello","Hola"]. Adding quarkus-resteasy-reactive-jackson to a classpath does not solve the problem.

Expected behaviour

Any of the following:
Returning of valid json array (["Hello","Hola"])
Returning values one-by-one
Compilation error

Actual behavior

Invalid json array([Hello,Hola])

To Reproduce

Link to a reproducer:

git clone [email protected]:fedinskiy/reproducer.git -b multi-jackson

Steps to reproduce the behavior:

1. mvn clean quarkus:dev
2. curl -w'\n' localhost:8080/hello/multi
   Or:
3. mvn clean test

Environment (please complete the following information):

Output of uname -a or ver

Linux localhost.localdomain 5.12.10-300.fc34.x86_64 #1 SMP Thu Jun 10 14:21:36 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

Output of java -version

openjdk 11.0.11 2021-04-20
OpenJDK Runtime Environment GraalVM CE 20.3.2 (build 11.0.11+8-jvmci-20.3-b15)
OpenJDK 64-Bit Server VM GraalVM CE 20.3.2 (build 11.0.11+8-jvmci-20.3-b15, mixed mode, sharing)

Quarkus version or git rev

2.0.0.CR3
OR
1.13.7.Final

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

Apache Maven 3.6.3

May be somehow connected to #14183

[quarkus-bot]

/cc @FroMage, @geoand, @stuartwdouglas

[oliver-brm]

The items in the Multi<String> hit a condition in JacksonMessageBodyWriterUtil:

if (o instanceof String) { // YUK: done in order to avoid adding extra quotes...
    entityStream.write(((String) o).getBytes());
} else {
    ...

Removing the condition would fix this issue but I'm not sure if it would raise other issues.

[geoand]

Removing the condition would fix this issue but I'm not sure if it would raise other issues.

Unfortunately it would

[StephenOTT]

Is there a workaround for this?

[StephenOTT]

The workaround for me was to just wrap the strings in another object