Write SSE headers before subscribing

[cescoffier]

When using SSE send the headers (and flush them) as soon as we have the Publisher (so before subscription).

Fix #22762

[gsmet]

@cescoffier is it something we should backport? It looks annoying for people using SSE?

[cescoffier]

@gsmet Yes, but let's wait for the CI to complete first :-D

[cescoffier]

My first fix not totally correct. I'm more confident with this one.

[quarkus-bot]

This workflow status is outdated as a new workflow run has been triggered.

Failing Jobs - Building f0d8337

Status	Name	Step	Failures	Logs	Raw logs
✖	Gradle Tests - JDK 11 Windows	Build	Failures	Logs	Raw logs
✖	JVM Tests - JDK 11	Build	Failures	Logs	Raw logs
✖	JVM Tests - JDK 11 Windows	Build	Failures	Logs	Raw logs
✖	JVM Tests - JDK 17	Build	Failures	Logs	Raw logs

Full information is available in the Build summary check run.

Failures

⚙️ Gradle Tests - JDK 11 Windows #

- Failing: integration-tests/gradle 

📦 integration-tests/gradle

✖ io.quarkus.gradle.devmode.JandexMultiModuleProjectDevModeTest.main line 21 - More details - Source on GitHub

org.awaitility.core.ConditionTimeoutException: Condition with lambda expression in io.quarkus.test.devmode.util.DevModeTestUtils that uses java.util.function.Supplier, java.util.function.Supplierjava.util.concurrent.atomic.AtomicReference, java.util.concurrent.atomic.AtomicReferencejava.lang.String, java.lang.Stringboolean was not fulfilled within 1 minutes.
	at org.awaitility.core.ConditionAwaiter.await(ConditionAwaiter.java:164)
	at org.awaitility.core.CallableCondition.await(CallableCondition.java:78)

---

⚙️ JVM Tests - JDK 11 #

- Failing: extensions/resteasy-reactive/quarkus-resteasy-reactive/deployment 
! Skipped: extensions/apicurio-registry-avro/deployment extensions/avro/deployment extensions/grpc/deployment and 87 more

📦 extensions/resteasy-reactive/quarkus-resteasy-reactive/deployment

✖ io.quarkus.resteasy.reactive.server.test.stream.StreamTestCase.testSse line 214 - More details - Source on GitHub

org.opentest4j.AssertionFailedError: expected: <[a, b, c]> but was: <[]>
	at org.junit.jupiter.api.AssertionUtils.fail(AssertionUtils.java:55)
	at org.junit.jupiter.api.AssertionUtils.failNotEqual(AssertionUtils.java:62)

---

⚙️ JVM Tests - JDK 11 Windows #

- Failing: extensions/resteasy-reactive/quarkus-resteasy-reactive-jackson/deployment extensions/resteasy-reactive/quarkus-resteasy-reactive-jaxb/deployment extensions/resteasy-reactive/quarkus-resteasy-reactive-jsonb/deployment 
! Skipped: extensions/hibernate-reactive/deployment extensions/oidc-client-reactive-filter/deployment extensions/oidc-token-propagation-reactive/deployment and 34 more

📦 extensions/resteasy-reactive/quarkus-resteasy-reactive-jackson/deployment

✖ io.quarkus.resteasy.reactive.jackson.deployment.test.sse.SseTestCase.testJsonMultiFromMultiWithDefaultElementType line 114 - More details - Source on GitHub

java.lang.AssertionError: 
[Extracted: name] 
Expecting actual:

✖ io.quarkus.resteasy.reactive.jackson.deployment.test.sse.SseTestCase.testJsonMultiFromMulti line 109 - More details - Source on GitHub

java.lang.AssertionError: 
[Extracted: name] 
Expecting actual:

✖ io.quarkus.resteasy.reactive.jackson.deployment.test.sse.SseTestCase.testMultiFromMulti line 89 - More details - Source on GitHub

java.lang.AssertionError: 

Expecting actual:

✖ io.quarkus.resteasy.reactive.jackson.deployment.test.sse.SseTestCase.testSseFromMulti line 53 - More details - Source on GitHub

java.lang.AssertionError: 

Expecting actual:

📦 extensions/resteasy-reactive/quarkus-resteasy-reactive-jaxb/deployment

✖ io.quarkus.resteasy.reactive.jaxb.deployment.test.SseResourceTest.testMultiFromMulti line 92 - More details - Source on GitHub

java.lang.AssertionError: 

Expecting actual:

✖ io.quarkus.resteasy.reactive.jaxb.deployment.test.SseResourceTest.testSseFromMulti line 56 - More details - Source on GitHub

java.lang.AssertionError: 

Expecting actual:

📦 extensions/resteasy-reactive/quarkus-resteasy-reactive-jsonb/deployment

✖ io.quarkus.resteasy.reactive.jsonb.deployment.test.sse.SseTestCase.testJsonMultiFromMultiWithDefaultElementType line 112 - More details - Source on GitHub

java.lang.AssertionError: 
[Extracted: name] 
Expecting actual:

✖ io.quarkus.resteasy.reactive.jsonb.deployment.test.sse.SseTestCase.testJsonMultiFromMulti line 107 - More details - Source on GitHub

java.lang.AssertionError: 
[Extracted: name] 
Expecting actual:

✖ io.quarkus.resteasy.reactive.jsonb.deployment.test.sse.SseTestCase.testMultiFromMulti line 87 - More details - Source on GitHub

java.lang.AssertionError: 

Expecting actual:

✖ io.quarkus.resteasy.reactive.jsonb.deployment.test.sse.SseTestCase.testSseFromMulti line 51 - More details - Source on GitHub

java.lang.AssertionError: 

Expecting actual:

---

⚙️ JVM Tests - JDK 17 #

- Failing: extensions/resteasy-reactive/quarkus-resteasy-reactive/deployment 
! Skipped: extensions/apicurio-registry-avro/deployment extensions/avro/deployment extensions/grpc/deployment and 87 more

📦 extensions/resteasy-reactive/quarkus-resteasy-reactive/deployment

✖ io.quarkus.resteasy.reactive.server.test.stream.StreamTestCase.testSse line 214 - More details - Source on GitHub

org.opentest4j.AssertionFailedError: expected: <[a, b, c]> but was: <[]>
	at org.junit.jupiter.api.AssertionUtils.fail(AssertionUtils.java:55)
	at org.junit.jupiter.api.AssertionUtils.failNotEqual(AssertionUtils.java:62)