Fix regression in ProducesRequestCondition

Closes gh-22853

Author: rstoyanchev

spring-webflux/src/main/java/org/springframework/web/reactive/result/condition/ProducesRequestCondition.java

@@ -185,9 +185,12 @@ public ProducesRequestCondition combine(ProducesRequestCondition other) {
 	@Override
 	@Nullable
 	public ProducesRequestCondition getMatchingCondition(ServerWebExchange exchange) {
-		if (isEmpty() || CorsUtils.isPreFlightRequest(exchange.getRequest())) {
+		if (CorsUtils.isPreFlightRequest(exchange.getRequest())) {
 			return EMPTY_CONDITION;
 		}
+		if (isEmpty()) {
+			return this;
+		}
 		Set<ProduceMediaTypeExpression> result = new LinkedHashSet<>(this.expressions);
 		result.removeIf(expression -> !expression.match(exchange));
 		if (!result.isEmpty()) {

spring-webflux/src/test/java/org/springframework/web/reactive/result/condition/ProducesRequestConditionTests.java

@@ -21,15 +21,14 @@
 
 import org.junit.Test;
 
+import org.springframework.http.MediaType;
 import org.springframework.mock.web.test.server.MockServerWebExchange;
+import org.springframework.web.reactive.accept.RequestedContentTypeResolver;
+import org.springframework.web.reactive.accept.RequestedContentTypeResolverBuilder;
 import org.springframework.web.server.ServerWebExchange;
 
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertNotNull;
-import static org.junit.Assert.assertNull;
-import static org.junit.Assert.assertTrue;
-import static org.junit.Assert.fail;
-import static org.springframework.mock.http.server.reactive.test.MockServerHttpRequest.get;
+import static org.junit.Assert.*;
+import static org.springframework.mock.http.server.reactive.test.MockServerHttpRequest.*;
 
 /**
  * Unit tests for {@link ProducesRequestCondition}.
@@ -110,6 +109,23 @@ public void matchWithNegationAndMediaTypeAllWithQualityParameter() {
 		assertNotNull(condition.getMatchingCondition(exchange));
 	}
 
+	@Test // gh-22853
+	public void matchAndCompare() {
+		RequestedContentTypeResolverBuilder builder = new RequestedContentTypeResolverBuilder();
+		builder.headerResolver();
+		builder.fixedResolver(MediaType.TEXT_HTML);
+		RequestedContentTypeResolver resolver = builder.build();
+
+		ProducesRequestCondition none = new ProducesRequestCondition(new String[0], null, resolver);
+		ProducesRequestCondition html = new ProducesRequestCondition(new String[] {"text/html"}, null, resolver);
+
+		MockServerWebExchange exchange = MockServerWebExchange.from(get("/").header("Accept", "*/*"));
+
+		ProducesRequestCondition noneMatch = none.getMatchingCondition(exchange);
+		ProducesRequestCondition htmlMatch = html.getMatchingCondition(exchange);
+
+		assertEquals(1, noneMatch.compareTo(htmlMatch, exchange));
+	}
 
 	@Test
 	public void compareTo() {

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/condition/ProducesRequestCondition.java

@@ -185,18 +185,19 @@ public ProducesRequestCondition combine(ProducesRequestCondition other) {
 	@Override
 	@Nullable
 	public ProducesRequestCondition getMatchingCondition(HttpServletRequest request) {
-		if (isEmpty() || CorsUtils.isPreFlightRequest(request)) {
+		if (CorsUtils.isPreFlightRequest(request)) {
 			return EMPTY_CONDITION;
 		}
-
+		if (isEmpty()) {
+			return this;
+		}
 		List<MediaType> acceptedMediaTypes;
 		try {
 			acceptedMediaTypes = getAcceptedMediaTypes(request);
 		}
 		catch (HttpMediaTypeException ex) {
 			return null;
 		}
-
 		Set<ProduceMediaTypeExpression> result = new LinkedHashSet<>(this.expressions);
 		result.removeIf(expression -> !expression.match(acceptedMediaTypes));
 		if (!result.isEmpty()) {

spring-webmvc/src/test/java/org/springframework/web/servlet/mvc/condition/ProducesRequestConditionTests.java

@@ -21,7 +21,11 @@
 
 import org.junit.Test;
 
+import org.springframework.http.MediaType;
 import org.springframework.mock.web.test.MockHttpServletRequest;
+import org.springframework.web.accept.ContentNegotiationManager;
+import org.springframework.web.accept.FixedContentNegotiationStrategy;
+import org.springframework.web.accept.HeaderContentNegotiationStrategy;
 import org.springframework.web.servlet.mvc.condition.ProducesRequestCondition.ProduceMediaTypeExpression;
 
 import static org.junit.Assert.*;
@@ -139,6 +143,24 @@ public void matchWithNegationAndMediaTypeAllWithQualityParameter() {
 		assertNotNull(condition.getMatchingCondition(request));
 	}
 
+	@Test // gh-22853
+	public void matchAndCompare() {
+		ContentNegotiationManager manager = new ContentNegotiationManager(
+				new HeaderContentNegotiationStrategy(),
+				new FixedContentNegotiationStrategy(MediaType.TEXT_HTML));
+
+		ProducesRequestCondition none = new ProducesRequestCondition(new String[0], null, manager);
+		ProducesRequestCondition html = new ProducesRequestCondition(new String[] {"text/html"}, null, manager);
+
+		MockHttpServletRequest request = new MockHttpServletRequest();
+		request.addHeader("Accept", "*/*");
+
+		ProducesRequestCondition noneMatch = none.getMatchingCondition(request);
+		ProducesRequestCondition htmlMatch = html.getMatchingCondition(request);
+
+		assertEquals(1, noneMatch.compareTo(htmlMatch, request));
+	}
+
 	@Test
 	public void compareTo() {
 		ProducesRequestCondition html = new ProducesRequestCondition("text/html");