Spring allow-bean-definition-overriding not working as expected

Spring boot version: [2.1.6.RELEASE, 2.2.1.RELEASE]

package a.b;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class Foo { 
  public static void main(String[] args) { 
    new SpringApplicationBuilder(Foo.class)
        .run(args);
  }
}

package a.c;

import org.springframework.stereotype.Service;

@Service
public class Foo {}

application.properties contains following property

spring.main.allow-bean-definition-overriding=false

Expectation
Failure on startup because two beans with name foo are not supposed to be registered.

Reality No exception and silently the non-main class bean is left out. (i.e. bean with name foo is registered with class a.b.Foo)

Note: This is only the case when another bean contributor is the entry-point Spring boot application class.

Comment From: wilkinsona

Thanks for raising an issue, @JigarJoshi. From our discussion on Gitter:

Could you open a Spring Framework issue for that please? ClassPathBeanDefinitionScanner considers the bean definitions for a.b.Foo and a.c.Foo to be compatible so it keeps the first one (a.b.Foo) and ignores the second one. That doesn't seem right to me.

Comment From: snicoll

I can't reproduce the issue. Besides the example above would not work given that a.c is not going to be a target of classpath scanning with a Spring Boot app in a.b.

Here is the exception I get:

Caused by: org.springframework.context.annotation.ConflictingBeanDefinitionException: Annotation-specified bean name 'foo' for bean class [com.a.b.Foo] conflicts with existing, non-compatible bean definition of same name and class [com.a.Foo]
    at org.springframework.context.annotation.ClassPathBeanDefinitionScanner.checkCandidate(ClassPathBeanDefinitionScanner.java:361) ~[spring-context-6.1.1-SNAPSHOT.jar:6.1.1-SNAPSHOT]
    at org.springframework.context.annotation.ClassPathBeanDefinitionScanner.doScan(ClassPathBeanDefinitionScanner.java:288) ~[spring-context-6.1.1-SNAPSHOT.jar:6.1.1-SNAPSHOT]
    at org.springframework.context.annotation.ComponentScanAnnotationParser.parse(ComponentScanAnnotationParser.java:128) ~[spring-context-6.1.1-SNAPSHOT.jar:6.1.1-SNAPSHOT]
    at org.springframework.context.annotation.ConfigurationClassParser.doProcessConfigurationClass(ConfigurationClassParser.java:296) ~[spring-context-6.1.1-SNAPSHOT.jar:6.1.1-SNAPSHOT]
    at org.springframework.context.annotation.ConfigurationClassParser.processConfigurationClass(ConfigurationClassParser.java:245) ~[spring-context-6.1.1-SNAPSHOT.jar:6.1.1-SNAPSHOT]
    at org.springframework.context.annotation.ConfigurationClassParser.parse(ConfigurationClassParser.java:196) ~[spring-context-6.1.1-SNAPSHOT.jar:6.1.1-SNAPSHOT]
    at org.springframework.context.annotation.ConfigurationClassParser.parse(ConfigurationClassParser.java:164) ~[spring-context-6.1.1-SNAPSHOT.jar:6.1.1-SNAPSHOT]
    ... 11 common frames omitted

Can you please move that code snippet into an actual project we can run? You can attach a zip to this issue or push the code to a GitHub repository.

Comment From: spring-projects-issues

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Comment From: spring-projects-issues

Closing due to lack of requested feedback. If you would like us to look at this issue, please provide the requested information and we will re-open the issue.