Checks the existence of 'dependsOn' beans before adding them to BeanDefinition

[nosan]

Consider the following example:

public class EmbeddedMongoAutoConfigurationTests {

	private AnnotationConfigApplicationContext context;

	@After
	public void close() {
		if (this.context != null) {
			this.context.close();
		}
	}

	@Test
	public void customMongoServer() {
		load(CustomMongoConfiguration.class);
	}

	private void load(Class<?> config, String... environment) {
		AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
		if (config != null) {
			ctx.register(config);
		}
		TestPropertyValues.of(environment).applyTo(ctx);
		ctx.register(EmbeddedMongoAutoConfiguration.class, MongoAutoConfiguration.class,
				PropertyPlaceholderAutoConfiguration.class);
		ctx.refresh();
		this.context = ctx;
	}

	@Configuration
	static class CustomMongoConfiguration {

		@Bean(initMethod = "start", destroyMethod = "stop")
		public MongodExecutable customMongoServer(IMongodConfig mongodConfig,
				IRuntimeConfig runtimeConfig, ApplicationContext context) throws IOException {
			MongodStarter mongodStarter = MongodStarter.getInstance(runtimeConfig);
			return mongodStarter.prepare(mongodConfig);
		}

	}
}

This test does not work because of

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'mongo' defined in org.springframework.boot.autoconfigure.mongo.MongoAutoConfiguration: 'mongo' depends on missing bean 'embeddedMongoServer'; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'embeddedMongoServer' available

	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:310)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:849)
	at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
	...
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'embeddedMongoServer' available
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeanDefinition(DefaultListableBeanFactory.java:775)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getMergedLocalBeanDefinition(AbstractBeanFactory.java:1221)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:294)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:307)
	... 31 more

So, If we define a custom bean with a different name from embeddedMongoServer, ApplicationContext will not start, as EmbeddedMongoDependencyConfiguration has added dependsOn to { MongoClient.class, MongoClientFactoryBean.class } beans, but embeddedMongoServer has not existed anymore as it was substituted by a custom bean.

This PR tries to fix this.

Thanks

[philwebb]

Thanks for the PR, but I feel like this change might just mask problems and make them harder to diagnose. I think instead we should change the depends on checks in EmbeddedMongoAutoConfiguration to be based on type rather than name. I've raised #16540 to look into that.