Watcher API watcher_get_settings does not return "X-elastic-product" header

[ldematte]

Elasticsearch Version

8.12

Installed Plugins

No response

Java Version

bundled

OS Version

N/A

Problem Description

I was fixing an error that omitted the elastic product header checks for V8 (

elasticsearch/test/yaml-rest-runner/src/main/java/org/elasticsearch/test/rest/yaml/section/DoSection.java

Lines 366 to 369 in 8be0446

	if (executionContext.esVersion().major == Version.V_7_17_0.major && executionContext.esVersion().after(Version.V_7_17_1)) {
	// #84038 and #84089 mean that this assertion fails when running against a small number of 7.17.x released versions
	checkElasticProductHeader(response.getHeaders("X-elastic-product"));
	}

).
However, by doing that WatcherYamlRestIT » test {p0=watcher/update_settings/10_update_watcher_settings/Test update and get watch settings api} starts to fail.
The "X-elastic-product" header is really missing from the headers. I suspect this bug is due to these lines:

elasticsearch/x-pack/plugin/watcher/src/main/java/org/elasticsearch/xpack/watcher/transport/actions/TransportGetWatcherSettingsAction.java

Lines 65 to 73 in f77c16b

	// Stashing and un-stashing the context allows warning headers about accessing a system index to be ignored.
	try (ThreadContext.StoredContext ignore = threadContext.stashContext()) {
	IndexMetadata metadata = state.metadata().index(WATCHER_INDEX_NAME);
	if (metadata == null) {
	listener.onResponse(new GetWatcherSettingsAction.Response(Settings.EMPTY));
	} else {
	listener.onResponse(new GetWatcherSettingsAction.Response(filterSettableSettings(metadata.getSettings())));
	}
	}

That clear up the context in the response.

Steps to Reproduce

The bug is present in all versions from 8.8.0 to current; to trigger it is sufficient to call the API and observer the resulting response, and see that the product header is not there.

A way to do that is to remove the if here (

elasticsearch/test/yaml-rest-runner/src/main/java/org/elasticsearch/test/rest/yaml/section/DoSection.java

Lines 366 to 369 in 8be0446

	if (executionContext.esVersion().major == Version.V_7_17_0.major && executionContext.esVersion().after(Version.V_7_17_1)) {
	// #84038 and #84089 mean that this assertion fails when running against a small number of 7.17.x released versions
	checkElasticProductHeader(response.getHeaders("X-elastic-product"));
	}

) and run linked failing tests, e.g.
./gradlew ':x-pack:plugin:watcher:qa:rest:yamlRestTest' --tests "org.elasticsearch.smoketest.WatcherYamlRestIT.test {p0=watcher/update_settings/10_update_watcher_settings/Test update and get watch settings api}"

Logs (if relevant)

No response

[elasticsearchmachine]

Pinging @elastic/es-data-management (Team:Data Management)

[ldematte]

Link to the issues fixing the version check: #102929
The problem can be observed in the failing build scan

[ldematte]

Fix here #103003 ready for review