Json stream item is not processed immediately after receiving in ChunkedStreamingMultiSubscriber.class

[paloliska]

Describe the bug

When using rest endpoint with application/stream+json content type, after receiving json object is not processed immediately.
Client is expecting stream element separator to process element. Separator is sent as prefix with subsequent elements. This means that stream element is processed after receiving next one.

Expected behavior

Stream element should be processed immediately after receiving.

Maybe ChunkedStreamingMultiSubscriber should add separator as postfix, not as prefix with next item.

Actual behavior

Strem element is processed after receiving next one (or stream closed).

How to Reproduce?

Reproducer: https://github.com/paloliska/json-stream

steps:

1. Run test in reproducer project.

Output of uname -a or ver

Linux user 5.15.0-58-generic #64-Ubuntu SMP Thu Jan 5 11:43:13 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux

Output of java -version

openjdk version "17.0.5" 2022-10-18

GraalVM version (if different from Java)

No response

Quarkus version or git rev

2.16.0.Final, 3.0.1.Final

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

Apache Maven 3.6.3

Additional information

No response

[quarkus-bot]

/cc @FroMage (resteasy-reactive), @Sgitario (resteasy-reactive), @stuartwdouglas (resteasy-reactive)

[geoand]

@Sgitario mind taking a look at this?

[Sgitario]

Fix: #30737

[paloliska]

issue updated with reproducer for quarkus 3.0.1.Final