NoClassDefFoundError: org/hibernate/community/dialect/CommunityDatabase when no default datasource

[HerrDerb]

Describe the bug

With PR #48130 the usage of the class CommunityDatabase got introduce in the HibernateProcessorUtil#L241

When building a project with no default datasource (multi tenancy, in which we provide the tenant datasources at runtime), this causes

	[error]: Build step io.quarkus.hibernate.orm.deployment.HibernateOrmProcessor#configurationDescriptorBuilding threw an exception: java.lang.NoClassDefFoundError: org/hibernate/community/dialect/CommunityDatabase
        	at io.quarkus.hibernate.orm.deployment.util.HibernateProcessorUtil.lambda$supportedDatabaseKindFromProductName$2(HibernateProcessorUtil.java:241)
        	at java.base/java.util.Optional.flatMap(Optional.java:289)
        	at io.quarkus.hibernate.orm.deployment.util.HibernateProcessorUtil.supportedDatabaseKindFromProductName(HibernateProcessorUtil.java:236)
        	at io.quarkus.hibernate.orm.deployment.util.HibernateProcessorUtil.lambda$determineDatabaseKind$0(HibernateProcessorUtil.java:228)

The reason for this seems that no JdbcDataSourceBuildItem with default = true exists, of which the db kind can be read from.
This causes the dbKindOptional HibernateProcessorUtil.java#L226 to be empty, hence calling the method HibernateProcessorUtil.supportedDatabaseKindFromProductName. This again will cause the NoClassDefFoundError as, without the hibernate-orm-derby extension, the class CommunityDatabase is not provided (current providing of the hibernate-community-dialects might be probably an issue itself)

Quarkus version or git rev

3.26.4

Expected behaviour

Without a default datasource, the db kind still should be read from the configuration property

[quarkus-bot]

/cc @gsmet (hibernate-orm)

[geoand]

cc @yrodiere

[yrodiere]

Thanks for the report.

The bug is definitely in here:

https://github.com/quarkusio/quarkus/blob/main/extensions/hibernate-orm/deployment/src/main/java/io/quarkus/hibernate/orm/deployment/util/HibernateProcessorUtil.java#L241

We simply shouldn't be referring to CommunityDatabase directly.