Using the latest blade and service builder, ds as the default dependency injection, if you have an <entity /> in the service.xml file with a compound primary key, when service builder generates the code, the API module will have the service/persistence/<entity>PK class (for the primary key).
This class has dependencies on two petra modules, com.liferay.petra.lang and com.liferay.petra.string. However, SB does not inject these dependencies into the build.gradle file, so builds fail without manual cleanup of the generated code.
The two classes the PK will depend upon are:
This may be a bug w/ other versions of SB under 7.2 with the DS injection or even go beyond the DS injection; I was at least able to see this happening on 7.2.10 sp1.