I've noticed that the module.xml files for the various driver modules in wildfly-datasources-galleon-pack, e.g. [1], include a dependency on the 'javax.transaction.api' module. I wonder if this is needed and if there's a good way to check if not.

The javax.transaction.xa package is required by JDBC, but that package comes from Java SE and is not exposed by our 'javax.transaction.api' module. Our module exposes the Jakarta Transactions API, which, even in its EE 8 javax namespace form did not include javax.transaction.xa. Use of the Jakarta Transactions API is not part of the JDBC spec, so it's not a given that a 'javax.transaction.api' module dep is needed.

I suppose it's possible that one or more of the drivers we support in wildfly-datasources-galleon-pack uses JTA internally, or did in some release, in which case removing the module.xml dep would break things. Note though that use of EE 8 Jakarta Transactions wouldn't work anyway for WF Preview or standard WildFly 27 and later, as those server versions do not expose jakarta.* namespace JTA.