Register original bean name as alias if not taken already

Closes gh-37038

spring-context/src/main/java/org/springframework/context/annotation/ConfigurationBeanNameGenerator.java

@@ -38,9 +38,11 @@ public interface ConfigurationBeanNameGenerator extends BeanNameGenerator {
 	/**
 	 * Derive a default bean name for the given {@link Bean @Bean} method,
 	 * taking into account the specified {@link Bean#name() name} attribute.
+	 * <p>As of 7.1, the original {@code @Bean} name (typically the method name)
+	 * will be registered as an alias if that name has not been taken already.
 	 * @param beanMethod the method metadata for the {@link Bean @Bean} method
-	 * @param beanName the {@link Bean#name() name} attribute or {@code null} if
-	 * none is specified
+	 * @param beanName the {@link Bean#name() name} attribute or {@code null}
+	 * if none is specified
 	 * @return the default bean name to use
 	 */
 	String deriveBeanName(MethodMetadata beanMethod, @Nullable String beanName);

spring-context/src/main/java/org/springframework/context/annotation/ConfigurationClassBeanDefinitionReader.java

@@ -210,6 +210,11 @@ class ConfigurationClassBeanDefinitionReader {
 		String localBeanName = defaultBeanName(beanName, methodName);
 		beanName = (this.importBeanNameGenerator instanceof ConfigurationBeanNameGenerator cbng ?
 				cbng.deriveBeanName(metadata, beanName) : localBeanName);
+		if (!localBeanName.equals(beanName) && !this.registry.containsBeanDefinition(localBeanName) &&
+				!this.registry.isAlias(localBeanName)) {
+			// Register original name as alias unless registered already.
+			this.registry.registerAlias(beanName, localBeanName);
+		}
 		if (explicitNames.length > 0) {
 			// Register aliases even when overridden below.
 			for (int i = 1; i < explicitNames.length; i++) {

spring-context/src/main/java/org/springframework/context/annotation/FullyQualifiedConfigurationBeanNameGenerator.java

@@ -32,10 +32,13 @@ import org.springframework.core.type.MethodMetadata;
  * {@code @Bean} methods (which uses the plain method name), primarily for use
  * in large applications with potential bean name overlaps. Favor this bean
  * naming strategy over {@code FullyQualifiedAnnotationBeanNameGenerator} if
- * you expect such naming conflicts for {@code @Bean} methods, as long as the
- * application does not depend on {@code @Bean} method names as bean names.
- * Where the name does matter, make sure to declare {@code @Bean("myBeanName")}
- * in such a scenario, even if it repeats the method name as the bean name.
+ * you expect such naming conflicts for {@code @Bean} methods.
+ *
+ * <p>As of 7.1, the original {@code @Bean} method name will be registered
+ * as an alias if that name has not been taken already: effectively on first
+ * occurrence, whereas any later {@code @Bean} methods of the same name will
+ * not have aliases applied. This preserves the availability of common beans
+ * under the original bean names for retrieval and injection purposes.
  *
  * @author Juergen Hoeller
  * @since 7.0

spring-context/src/test/java/org/springframework/context/annotation/AnnotationConfigApplicationContextTests.java

@@ -105,10 +105,31 @@ class AnnotationConfigApplicationContextTests {
 		context.getBean(Config.class.getName() + ".testBean");
 		assertThat(context.getBean(NameConfig.class.getName() + ".name")).isEqualTo("foo");
 		assertThat(context.getBean(NameConfig.class.getName() + ".prefixName")).isEqualTo("barfoo");
+		assertThat(context.getBean("name")).isEqualTo("foo");
+		assertThat(context.getBean("prefixName")).isEqualTo("barfoo");
 		Map<String, Object> beans = context.getBeansWithAnnotation(Configuration.class);
 		assertThat(beans).hasSize(2);
 	}
 
+	@Test
+	void registerAndRefreshWithOverlappingFullyQualifiedBeanNames() {
+		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
+		context.setBeanNameGenerator(FullyQualifiedConfigurationBeanNameGenerator.INSTANCE);
+		context.setAllowBeanDefinitionOverriding(false);
+		context.register(Config.class, NameConfig.class, OtherNameConfig.class);
+		context.refresh();
+
+		context.getBean(Config.class.getName() + ".testBean");
+		assertThat(context.getBean(NameConfig.class.getName() + ".name")).isEqualTo("foo");
+		assertThat(context.getBean(NameConfig.class.getName() + ".prefixName")).isEqualTo("barfoo");
+		assertThat(context.getBean(OtherNameConfig.class.getName() + ".name")).isEqualTo("fooX");
+		assertThat(context.getBean(OtherNameConfig.class.getName() + ".prefixName")).isEqualTo("barXfooX");
+		assertThat(context.getBean("name")).isEqualTo("foo");
+		assertThat(context.getBean("prefixName")).isEqualTo("barfoo");
+		Map<String, Object> beans = context.getBeansWithAnnotation(Configuration.class);
+		assertThat(beans).hasSize(3);
+	}
+
 	@Test
 	void getBeansWithAnnotation() {
 		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
@@ -632,6 +653,14 @@ class AnnotationConfigApplicationContextTests {
 		@Bean(autowireCandidate = false) String prefixName() { return "bar" + name(); }
 	}
 
+	@Configuration
+	static class OtherNameConfig {
+
+		@Bean String name() { return "fooX"; }
+
+		@Bean(autowireCandidate = false) String prefixName() { return "barX" + name(); }
+	}
+
 	@Configuration
 	@Import(NameConfig.class)
 	static class AutowiredConfig {