Improve compatibility with SnakeYAML 2.0

Closes gh-35414

Author: wilkinsona

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/env/OriginTrackedYamlLoader.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,9 @@
 
 package org.springframework.boot.env;
 
+import java.lang.invoke.MethodHandle;
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.MethodType;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
@@ -45,6 +48,7 @@
 import org.springframework.boot.origin.TextResourceOrigin;
 import org.springframework.boot.origin.TextResourceOrigin.Location;
 import org.springframework.core.io.Resource;
+import org.springframework.util.ReflectionUtils;
 
 /**
  * Class to load {@code .yml} files into a map of {@code String} to
@@ -73,8 +77,8 @@ protected Yaml createYaml() {
 
 	private Yaml createYaml(LoaderOptions loaderOptions) {
 		BaseConstructor constructor = new OriginTrackingConstructor(loaderOptions);
-		Representer representer = new Representer();
 		DumperOptions dumperOptions = new DumperOptions();
+		Representer representer = new Representer(dumperOptions);
 		LimitedResolver resolver = new LimitedResolver();
 		return new Yaml(constructor, representer, dumperOptions, loaderOptions, resolver);
 	}
@@ -167,7 +171,12 @@ private static Node get(Node node) {
 	/**
 	 * {@link Resolver} that limits {@link Tag#TIMESTAMP} tags.
 	 */
-	private static class LimitedResolver extends Resolver {
+	static class LimitedResolver extends Resolver {
+
+		private static final MethodType SNAKE_YAML_2_ADD_IMPLICIT_RESOLVER_METHOD_TYPE = MethodType
+				.methodType(void.class, Tag.class, Pattern.class, String.class, int.class);
+
+		private volatile MethodHandle snakeYaml2ImplicitResolverMethod;
 
 		@Override
 		public void addImplicitResolver(Tag tag, Pattern regexp, String first) {
@@ -177,6 +186,30 @@ public void addImplicitResolver(Tag tag, Pattern regexp, String first) {
 			super.addImplicitResolver(tag, regexp, first);
 		}
 
+		public void addImplicitResolver(Tag tag, Pattern regexp, String first, int limit) {
+			// Support for SnakeYAML 2.0
+			if (tag == Tag.TIMESTAMP) {
+				return;
+			}
+			try {
+				getSnakeYaml2ImplicitResolverMethod().invoke(this, tag, regexp, first, limit);
+			}
+			catch (Throwable ex) {
+				ReflectionUtils.rethrowRuntimeException(ex);
+			}
+		}
+
+		private MethodHandle getSnakeYaml2ImplicitResolverMethod()
+				throws NoSuchMethodException, IllegalAccessException {
+			MethodHandle snakeYaml2ImplicitResolverMethod = this.snakeYaml2ImplicitResolverMethod;
+			if (snakeYaml2ImplicitResolverMethod == null) {
+				snakeYaml2ImplicitResolverMethod = MethodHandles.lookup().findSpecial(Resolver.class,
+						"addImplicitResolver", SNAKE_YAML_2_ADD_IMPLICIT_RESOLVER_METHOD_TYPE, getClass());
+				this.snakeYaml2ImplicitResolverMethod = snakeYaml2ImplicitResolverMethod;
+			}
+			return snakeYaml2ImplicitResolverMethod;
+		}
+
 	}
 
 }

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/env/YamlPropertySourceLoaderSnakeYaml20Tests.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2012-2023 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.env;
+
+import org.springframework.boot.testsupport.classpath.ClassPathOverrides;
+
+/**
+ * Tests for {@link YamlPropertySourceLoader} with SnakeYAML 2.0.
+ *
+ * @author Andy Wilkinson
+ */
+@ClassPathOverrides("org.yaml:snakeyaml:2.0")
+class YamlPropertySourceLoaderSnakeYaml20Tests extends YamlPropertySourceLoaderTests {
+
+}

src/checkstyle/checkstyle-suppressions.xml

@@ -54,4 +54,5 @@
 	<suppress files="ValidatorPropertiesWithDefaultValues\.java" checks="SpringMethodVisibility" />
 	<suppress files="DevToolsR2dbcAutoConfigurationTests" checks="HideUtilityClassConstructor" />
 	<suppress files="AbstractLaunchScriptIntegrationTests" checks="IllegalImport" />
+	<suppress files="OriginTrackedYamlLoader" checks="SpringMethodVisibility" message="addImplicitResolver" />
 </suppressions>