Configure MessageSource if no "messageSource" bean defined

Enable MessageSourceAutoConfiguration OnMissingBeanCondition by name
rather than class since AbstractApplicationContext expects MessageSource
to be defined only with "messageSource" name.

See gh-15212

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/context/MessageSourceAutoConfiguration.java

@@ -33,6 +33,7 @@ import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.ConditionContext;
 import org.springframework.context.annotation.Conditional;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.context.support.AbstractApplicationContext;
 import org.springframework.context.support.ResourceBundleMessageSource;
 import org.springframework.core.Ordered;
 import org.springframework.core.io.Resource;
@@ -49,7 +50,7 @@ import org.springframework.util.StringUtils;
  * @author Eddú Meléndez
  */
 @Configuration
-@ConditionalOnMissingBean(value = MessageSource.class, search = SearchStrategy.CURRENT)
+@ConditionalOnMissingBean(name = AbstractApplicationContext.MESSAGE_SOURCE_BEAN_NAME, search = SearchStrategy.CURRENT)
 @AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE)
 @Conditional(ResourceBundleCondition.class)
 @EnableConfigurationProperties

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

@@ -198,6 +198,48 @@ public class MessageSourceAutoConfigurationTests {
 								.isEqualTo("bar")));
 	}
 
+	@Test
+	public void messageSourceDeclaredWithNonStandardNameDoesNotBreakAutoConfig() {
+		this.contextRunner.withPropertyValues("spring.messages.basename:test/messages")
+				.withUserConfiguration(ConfigWithNonStandardMessageSourceBeanName.class)
+				.run((context) -> {
+					assertThat(context.getMessage("foo", null, Locale.US))
+							.isEqualTo("bar");
+				});
+	}
+
+	private static class CodeReturningMessageSource implements MessageSource {
+
+		@Override
+		public String getMessage(String code, Object[] args, String defaultMessage,
+				Locale locale) {
+			return code;
+		}
+
+		@Override
+		public String getMessage(String code, Object[] args, Locale locale)
+				throws NoSuchMessageException {
+			return code;
+		}
+
+		@Override
+		public String getMessage(MessageSourceResolvable resolvable, Locale locale)
+				throws NoSuchMessageException {
+			return resolvable.getCodes()[0];
+		}
+
+	}
+
+	@Configuration
+	protected static class ConfigWithNonStandardMessageSourceBeanName {
+
+		@Bean
+		public MessageSource codeReturningMessageSource() {
+			return new CodeReturningMessageSource();
+		}
+
+	}
+
 	@Configuration
 	@PropertySource("classpath:/switch-messages.properties")
 	protected static class Config {
@@ -209,27 +251,7 @@ public class MessageSourceAutoConfigurationTests {
 
 		@Bean
 		public MessageSource messageSource() {
-			return new MessageSource() {
+			return new CodeReturningMessageSource();
-
-				@Override
-				public String getMessage(String code, Object[] args,
-						String defaultMessage, Locale locale) {
-					return code;
-				}
-
-				@Override
-				public String getMessage(String code, Object[] args, Locale locale)
-						throws NoSuchMessageException {
-					return code;
-				}
-
-				@Override
-				public String getMessage(MessageSourceResolvable resolvable,
-						Locale locale) throws NoSuchMessageException {
-					return resolvable.getCodes()[0];
-				}
-
-			};
 		}
 
 	}