Matrix parameters distort the values passed to a match all remaining selector when using WebFlux #52300

Spring Boot: 4.2.0-M2 (works in 4.1.1)

With Spring MVC, path parameters (for example a ;jsessionid=... added by URL rewriting) are no longer removed from the path segments passed to endpoint operations that use @Selector(match = Match.ALL_REMAINING). This breaks health group and component paths, and changes the values that custom endpoints receive.

With management.endpoint.health.probes.enabled=true, management.endpoint.health.show-components=always and management.endpoint.health.group.custom.include=ping,diskSpace:

For a custom endpoint:

@Endpoint(id = "echo")
class EchoEndpoint {

	@ReadOperation
	String echo(@Selector(match = Match.ALL_REMAINING) String... path) {
		return String.join("|", path);
	}

}

GET /actuator/echo/a/b;jsessionid=abc returns a|b in 4.1.1 and a|b;jsessionid=abc in 4.2.0-M2.

This seems to come from #51470. getRemainingPathSegments in AbstractWebMvcEndpointHandlerMapping now tokenizes pathPattern.extractPathWithinPattern(...).value(), which keeps path parameters, whereas the previous code used PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE.

Using the decoded value of each segment without its parameters restores the 4.1.1 behavior. I verified this locally against all the cases above, and the multi-segment additional paths from #51470 keep working:

PathContainer remainingPath = pathPattern
	.extractPathWithinPattern(ServletRequestPathUtils.getParsedRequestPath(request).pathWithinApplication());
return remainingPath.elements()
	.stream()
	.filter(PathContainer.PathSegment.class::isInstance)
	.map((element) -> ((PathContainer.PathSegment) element).valueToMatch())
	.filter(StringUtils::hasLength)
	.toArray(String[]::new);

I'd be happy to submit a PR with this change and a test.