Merge pull request #18675 from nosan

* pr/18675:
  Polish "Restore proxying of @Bean methods in @TestConfiguration"
  Restore proxying of @Bean methods in @TestConfiguration

Closes gh-18675

spring-boot-project/spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -6840,7 +6840,7 @@ The following example shows a `RestDocumentationResultHandler` being defined:
 
 [source,java,indent=0]
 ----
-	@TestConfiguration
+	@TestConfiguration(proxyBeanMethods = false)
 	static class ResultHandlerConfiguration {
 
 		@Bean

spring-boot-project/spring-boot-docs/src/main/java/org/springframework/boot/docs/test/autoconfigure/restdocs/restassured/AdvancedConfigurationExample.java

@@ -24,7 +24,7 @@ import org.springframework.restdocs.templates.TemplateFormats;
 public class AdvancedConfigurationExample {
 
 	// tag::configuration[]
-	@TestConfiguration
+	@TestConfiguration(proxyBeanMethods = false)
 	public static class CustomizationConfiguration implements RestDocsRestAssuredConfigurationCustomizer {
 
 		@Override

spring-boot-project/spring-boot-docs/src/main/java/org/springframework/boot/docs/test/autoconfigure/restdocs/webclient/AdvancedConfigurationExample.java

@@ -23,7 +23,7 @@ import org.springframework.restdocs.webtestclient.WebTestClientRestDocumentation
 public class AdvancedConfigurationExample {
 
 	// tag::configuration[]
-	@TestConfiguration
+	@TestConfiguration(proxyBeanMethods = false)
 	public static class CustomizationConfiguration implements RestDocsWebTestClientConfigurationCustomizer {
 
 		@Override

spring-boot-project/spring-boot-docs/src/test/java/org/springframework/boot/docs/web/client/SampleWebClientTests.java

@@ -49,7 +49,7 @@ class SampleWebClientTests {
 		assertThat(headers.getLocation()).hasHost("other.example.com");
 	}
 
-	@TestConfiguration
+	@TestConfiguration(proxyBeanMethods = false)
 	static class Config {
 
 		@Bean

spring-boot-project/spring-boot-test-autoconfigure/src/test/java/org/springframework/boot/test/autoconfigure/ExampleTestConfig.java

@@ -25,7 +25,7 @@ import org.springframework.boot.test.context.TestConfiguration;
  *
  * @author Phillip Webb
  */
-@TestConfiguration
+@TestConfiguration(proxyBeanMethods = false)
 @EntityScan("some.other.package")
 public class ExampleTestConfig {
 

spring-boot-project/spring-boot-test-autoconfigure/src/test/java/org/springframework/boot/test/autoconfigure/jdbc/AutoConfigureTestDatabaseWithNoDatabaseIntegrationTests.java

@@ -48,7 +48,7 @@ class AutoConfigureTestDatabaseWithNoDatabaseIntegrationTests {
 		assertThat(this.context.getBeanNamesForType(DataSource.class)).isNotEmpty();
 	}
 
-	@TestConfiguration
+	@TestConfiguration(proxyBeanMethods = false)
 	static class Config {
 
 	}

spring-boot-project/spring-boot-test-autoconfigure/src/test/java/org/springframework/boot/test/autoconfigure/restdocs/MockMvcRestDocsAutoConfigurationAdvancedConfigurationIntegrationTests.java

@@ -78,7 +78,7 @@ class MockMvcRestDocsAutoConfigurationAdvancedConfigurationIntegrationTests {
 		assertThat(new File(defaultSnippetsDir, "response-fields.md")).isFile();
 	}
 
-	@TestConfiguration
+	@TestConfiguration(proxyBeanMethods = false)
 	static class CustomizationConfiguration {
 
 		@Bean

spring-boot-project/spring-boot-test-autoconfigure/src/test/java/org/springframework/boot/test/autoconfigure/restdocs/RestAssuredRestDocsAutoConfigurationAdvancedConfigurationIntegrationTests.java

@@ -82,7 +82,7 @@ class RestAssuredRestDocsAutoConfigurationAdvancedConfigurationIntegrationTests
 		assertThat(new File(defaultSnippetsDir, "response-fields.md")).isFile();
 	}
 
-	@TestConfiguration
+	@TestConfiguration(proxyBeanMethods = false)
 	static class CustomizationConfiguration {
 
 		@Bean

spring-boot-project/spring-boot-test-autoconfigure/src/test/java/org/springframework/boot/test/autoconfigure/restdocs/WebTestClientRestDocsAutoConfigurationAdvancedConfigurationIntegrationTests.java

@@ -72,7 +72,7 @@ class WebTestClientRestDocsAutoConfigurationAdvancedConfigurationIntegrationTest
 		assertThat(new File(defaultSnippetsDir, "response-fields.md")).isFile();
 	}
 
-	@TestConfiguration
+	@TestConfiguration(proxyBeanMethods = false)
 	static class CustomizationConfiguration {
 
 		@Bean

spring-boot-project/spring-boot-test-autoconfigure/src/test/java/org/springframework/boot/test/autoconfigure/web/servlet/mockmvc/WebMvcTestServletFilterRegistrationDisabledIntegrationTests.java

@@ -44,7 +44,7 @@ class WebMvcTestServletFilterRegistrationDisabledIntegrationTests {
 		this.mvc.perform(get("/one")).andExpect(header().string("x-test", (String) null));
 	}
 
-	@TestConfiguration
+	@TestConfiguration(proxyBeanMethods = false)
 	static class DisabledRegistrationConfiguration {
 
 		@Bean

spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/context/TestConfiguration.java

@@ -23,6 +23,7 @@ import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
 import org.springframework.boot.SpringBootConfiguration;
+import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.core.annotation.AliasFor;
 
@@ -39,7 +40,7 @@ import org.springframework.core.annotation.AliasFor;
 @Target(ElementType.TYPE)
 @Retention(RetentionPolicy.RUNTIME)
 @Documented
-@Configuration(proxyBeanMethods = false)
+@Configuration
 @TestComponent
 public @interface TestConfiguration {
 
@@ -51,4 +52,29 @@ public @interface TestConfiguration {
 	@AliasFor(annotation = Configuration.class)
 	String value() default "";
 
+	/**
+	 * Specify whether {@link Bean @Bean} methods should get proxied in order to enforce
+	 * bean lifecycle behavior, e.g. to return shared singleton bean instances even in
+	 * case of direct {@code @Bean} method calls in user code. This feature requires
+	 * method interception, implemented through a runtime-generated CGLIB subclass which
+	 * comes with limitations such as the configuration class and its methods not being
+	 * allowed to declare {@code final}.
+	 * <p>
+	 * The default is {@code true}, allowing for 'inter-bean references' within the
+	 * configuration class as well as for external calls to this configuration's
+	 * {@code @Bean} methods, e.g. from another configuration class. If this is not needed
+	 * since each of this particular configuration's {@code @Bean} methods is
+	 * self-contained and designed as a plain factory method for container use, switch
+	 * this flag to {@code false} in order to avoid CGLIB subclass processing.
+	 * <p>
+	 * Turning off bean method interception effectively processes {@code @Bean} methods
+	 * individually like when declared on non-{@code @Configuration} classes, a.k.a.
+	 * "@Bean Lite Mode" (see {@link Bean @Bean's javadoc}). It is therefore behaviorally
+	 * equivalent to removing the {@code @Configuration} stereotype.
+	 * @return whether to proxy {@code @Bean} methods
+	 * @since 2.2.1
+	 */
+	@AliasFor(annotation = Configuration.class)
+	boolean proxyBeanMethods() default true;
+
 }

spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/context/TestConfigurationTests.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2012-2019 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.test.context;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.context.annotation.Configuration;
+import org.springframework.core.annotation.AnnotatedElementUtils;
+import org.springframework.core.annotation.AnnotationAttributes;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link TestConfiguration @TestConfiguration}.
+ *
+ * @author Stephane Nicoll
+ */
+class TestConfigurationTests {
+
+	@Test
+	void proxyBeanMethodsIsEnabledByDefault() {
+		AnnotationAttributes attributes = AnnotatedElementUtils
+				.getMergedAnnotationAttributes(DefaultTestConfiguration.class, Configuration.class);
+		assertThat(attributes.get("proxyBeanMethods")).isEqualTo(true);
+	}
+
+	@Test
+	void proxyBeanMethodsCanBeDisabled() {
+		AnnotationAttributes attributes = AnnotatedElementUtils
+				.getMergedAnnotationAttributes(NoBeanMethodProxyingTestConfiguration.class, Configuration.class);
+		assertThat(attributes.get("proxyBeanMethods")).isEqualTo(false);
+	}
+
+	@TestConfiguration
+	static class DefaultTestConfiguration {
+
+	}
+
+	@TestConfiguration(proxyBeanMethods = false)
+	static class NoBeanMethodProxyingTestConfiguration {
+
+	}
+
+}

spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/context/bootstrap/SpringBootTestContextBootstrapperIntegrationTests.java

@@ -67,7 +67,7 @@ class SpringBootTestContextBootstrapperIntegrationTests {
 		assertThat(this.defaultTestExecutionListenersPostProcessorCalled).isTrue();
 	}
 
-	@TestConfiguration
+	@TestConfiguration(proxyBeanMethods = false)
 	static class TestConfig {
 
 		@Bean