springboot @FlywayDataSource does not work in an application that has multiple datasources

I upgraded spring-boot version from 2.1.2 to 2.2.2 in my project. After upgrading, FlywayAutoConfiguration has been failed by NoUniqueBeanDefinitionException.

My application has multiple datasources and uses flyway whch uses the datasource is annotated with@FlywayDataSource. They are defined such as the following configuration class.

@Configuration
public class DataSourceConfig {
    @Bean
    @ConfigurationProperties(prefix = "datasource.main")
    public DataSource mainDataSource() {
        return DataSourceBuilder.create().build();
    }

    @Bean
    @ConfigurationProperties(prefix = "datasource.secondary")
    public DataSource secondaryDataSource() {
        return DataSourceBuilder.create().build();
    }

    @Bean
    @FlywayDataSource
    public DataSource flywayDataSource(DataSource mainDataSource) {
        return mainDataSource;
    }
}

This problem may have been caused by the change of this commit (https://github.com/spring-projects/spring-boot/commit/de0c065625d370cf6e1224d62111a764523b814e).

In version 2.1.2, getIfUnique() was called in FlywayAutoConfiguration.class to get a unique datasource.
https://github.com/spring-projects/spring-boot/blob/22e722d9f9f885d7fc67d51d16d68d55db6d6efc/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/flyway/FlywayAutoConfiguration.java#L136

But, in version 2.2.2 getIfAvailable() is called in FlywayAutoConfiguration.class to get a unique datasource.

https://github.com/spring-projects/spring-boot/blob/de0c065625d370cf6e1224d62111a764523b814e/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/flyway/FlywayAutoConfiguration.java#L119

Is this change the migration mistake ? as it is now, @FlywayDataSource does not work well for multiple datasources.

Comment From: wilkinsona

I don't recall intentionally making the switch from getIfUnique() to getIfAvailable() and suspect is was accidental. Thanks for letting us know.

Comment From: snicoll

Closing in favour of PR #20617