What does this error mean in Quarkus: "Model classes are defined for the default persistence unit but no default datasource found"

Question

As the title says, what does this exception message actually mean?

"Model classes are defined for the default persistence unit but no default datasource found: the default EntityManagerFactory will not be created"

Quarkus build fails with this cryptic error, but tests will run happily under JUnit/Intellij.

Answer 1

The issue was that in a multi-project build the correct configuration wasn't being included in a shared module. The exception message basically means that entities are present, but no configuration for oracle, or H2 etc