Fix WebFlux instrumentation after SPR-17395

SPR-17395 ensures that WebFlux.fn is adding a request attribute of type
`PathPattern` on the `HandlerMapping.BEST_MATCHING_PATTERN_ATTRIBUTE`.

A specific tag provider for WebFlux.fn is no longer necessary.

See spring-projectsgh-14876

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/metrics/web/reactive/server/WebFluxTags.java

@@ -21,7 +21,6 @@
 import org.springframework.http.HttpStatus;
 import org.springframework.util.StringUtils;
 import org.springframework.web.reactive.HandlerMapping;
-import org.springframework.web.reactive.function.server.RouterFunctions;
 import org.springframework.web.server.ServerWebExchange;
 import org.springframework.web.util.pattern.PathPattern;
 
@@ -87,9 +86,7 @@ public static Tag status(ServerWebExchange exchange) {
 
 	/**
 	 * Creates a {@code uri} tag based on the URI of the given {@code exchange}. Uses the
-	 * {@link HandlerMapping#BEST_MATCHING_PATTERN_ATTRIBUTE} best matching pattern from
-	 * WebFlux annotation or {@link RouterFunctions#MATCHING_PATTERN_ATTRIBUTE} from
-	 * WebFlux Fn.
+	 * {@link HandlerMapping#BEST_MATCHING_PATTERN_ATTRIBUTE} best matching pattern.
 	 * @param exchange the exchange
 	 * @return the uri tag derived from the exchange
 	 */
@@ -99,11 +96,6 @@ public static Tag uri(ServerWebExchange exchange) {
 		if (pathPattern != null) {
 			return Tag.of("uri", pathPattern.getPatternString());
 		}
-		String matchingPattern = exchange
-				.getAttribute(RouterFunctions.MATCHING_PATTERN_ATTRIBUTE);
-		if (matchingPattern != null) {
-			return Tag.of("uri", matchingPattern);
-		}
 		HttpStatus status = exchange.getResponse().getStatusCode();
 		if (status != null) {
 			if (status.is3xxRedirection()) {

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/metrics/web/reactive/server/WebFluxTagsTests.java

@@ -25,7 +25,6 @@
 import org.springframework.mock.http.server.reactive.MockServerHttpRequest;
 import org.springframework.mock.web.server.MockServerWebExchange;
 import org.springframework.web.reactive.HandlerMapping;
-import org.springframework.web.reactive.function.server.RouterFunctions;
 import org.springframework.web.server.ServerWebExchange;
 import org.springframework.web.util.pattern.PathPatternParser;
 
@@ -59,15 +58,6 @@ public void uriTagValueIsBestMatchingPatternWhenAvailable() {
 		assertThat(tag.getValue()).isEqualTo("/spring");
 	}
 
-	@Test
-	public void uriTagValueIsFnMatchingPatternWhenAvailable() {
-		this.exchange.getAttributes().put(RouterFunctions.MATCHING_PATTERN_ATTRIBUTE,
-				"/spring");
-		this.exchange.getResponse().setStatusCode(HttpStatus.MOVED_PERMANENTLY);
-		Tag tag = WebFluxTags.uri(this.exchange);
-		assertThat(tag.getValue()).isEqualTo("/spring");
-	}
-
 	@Test
 	public void uriTagValueIsRedirectionWhenResponseStatusIs3xx() {
 		this.exchange.getResponse().setStatusCode(HttpStatus.MOVED_PERMANENTLY);