Retain existing feature name as prefix in test AOT processing

Prior to this commit, test AOT processing failed if a feature name for
generated class names was used for more than one ApplicationContext.

For example, when generating code for org.example.MessageService with a
"Management" feature name, the "BeanDefinitions" class was named as
follows (without a uniquely identifying TestContext###_ feature name
prefix).

org/example/MessageService__ManagementBeanDefinitions.java

When another attempt was made to generate code for the MessageService
using the same "Management" feature name, a FileAlreadyExistsException
was thrown denoting that the class/file name was already in use.

To avoid such naming collisions, this commit introduces a
TestContextGenerationContext which provides a custom implementation of
withName(String) that prepends an existing feature name (if present) to
a new feature name, thereby treating any existing feature name as a
prefix to a new, nested feature name.

Consequently, code generation for the above example now results in
unique class/file names like the following (which retain the uniquely
identifying TestContext###_ prefixes).

org/example/MessageService__TestContext002_ManagementBeanDefinitions.java
org/example/MessageService__TestContext003_ManagementBeanDefinitions.java

Closes gh-30861

spring-test/src/main/java/org/springframework/test/context/aot/TestContextAotGenerator.java

@@ -324,8 +324,8 @@ public class TestContextAotGenerator {
 
 	DefaultGenerationContext createGenerationContext(Class<?> testClass) {
 		ClassNameGenerator classNameGenerator = new ClassNameGenerator(ClassName.get(testClass));
-		DefaultGenerationContext generationContext =
-				new DefaultGenerationContext(classNameGenerator, this.generatedFiles, this.runtimeHints);
+		TestContextGenerationContext generationContext =
+				new TestContextGenerationContext(classNameGenerator, this.generatedFiles, this.runtimeHints);
 		return generationContext.withName(nextTestContextId());
 	}
 

spring-test/src/main/java/org/springframework/test/context/aot/TestContextGenerationContext.java

@@ -0,0 +1,85 @@
+/*
+ * Copyright 2002-2023 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.test.context.aot;
+
+import org.springframework.aot.generate.ClassNameGenerator;
+import org.springframework.aot.generate.DefaultGenerationContext;
+import org.springframework.aot.generate.GeneratedClasses;
+import org.springframework.aot.generate.GeneratedFiles;
+import org.springframework.aot.hint.RuntimeHints;
+
+/**
+ * Extension of {@link DefaultGenerationContext} with a custom implementation of
+ * {@link #withName(String)} that is specific to the <em>Spring TestContext Framework</em>.
+ *
+ * @author Sam Brannen
+ * @since 6.0.12
+ */
+class TestContextGenerationContext extends DefaultGenerationContext {
+
+	private final String featureName;
+
+
+	/**
+	 * Create a new {@link TestContextGenerationContext} instance backed by the
+	 * specified {@link ClassNameGenerator}, {@link GeneratedFiles}, and
+	 * {@link RuntimeHints}.
+	 * @param classNameGenerator the naming convention to use for generated class names
+	 * @param generatedFiles the generated files
+	 * @param runtimeHints the runtime hints
+	 */
+	TestContextGenerationContext(ClassNameGenerator classNameGenerator, GeneratedFiles generatedFiles,
+			RuntimeHints runtimeHints) {
+		super(classNameGenerator, generatedFiles, runtimeHints);
+		this.featureName = null;
+	}
+
+	/**
+	 * Create a new {@link TestContextGenerationContext} instance backed by the
+	 * specified {@link GeneratedClasses}, {@link GeneratedFiles}, and
+	 * {@link RuntimeHints}.
+	 * @param generatedClasses the generated classes
+	 * @param generatedFiles the generated files
+	 * @param runtimeHints the runtime hints
+	 */
+	private TestContextGenerationContext(GeneratedClasses generatedClasses, GeneratedFiles generatedFiles,
+			RuntimeHints runtimeHints, String featureName) {
+		super(generatedClasses, generatedFiles, runtimeHints);
+		this.featureName = featureName;
+	}
+
+
+	/**
+	 * Create a new {@link TestContextGenerationContext} instance using the specified
+	 * feature name to qualify generated assets for a dedicated round of code generation.
+	 * <p>If <em>this</em> {@code TestContextGenerationContext} has a configured feature
+	 * name, the supplied feature name will be appended to the existing feature name
+	 * in order to avoid naming collisions.
+	 * @param featureName the feature name to use
+	 * @return a specialized {@link TestContextGenerationContext} for the specified
+	 * feature name
+	 */
+	@Override
+	public TestContextGenerationContext withName(String featureName) {
+		if (this.featureName != null) {
+			featureName = this.featureName + featureName;
+		}
+		GeneratedClasses generatedClasses = getGeneratedClasses().withFeatureNamePrefix(featureName);
+		return new TestContextGenerationContext(generatedClasses, getGeneratedFiles(), getRuntimeHints(), featureName);
+	}
+
+}