SVN rev 362 now incorporates further changes.
A sample script that has tests pass is shown below:
persistence setup --provider OPENJPA --database HYPERSONIC_IN_MEMORY
entity --name ~.Food --mappedSuperclass
field string --fieldName description --notNull
entity --name ~.Drink --extends ~.Food --testAutomatically
field number --fieldName ml --type java.lang.Integer --notNull
entity --name ~.Party --inheritanceType SINGLE_TABLE --abstract
field string --fieldName fullName --notNull
entity --name ~.Person --extends ~.Party --testAutomatically
field string --fieldName firstName --notNull
field string --fieldName lastName --notNull
I decided against the Roo commands offering advanced configuration options with respect to identifying the @DiscriminatorColumn and @DiscriminatorValue. The "entity" command was already quite complicated and now it is even more so due to the provision of these inheritance configuration features (specifically there is now a --inheritanceType and --mappedSuperclass option) and we need to draw the line somewhere given Roo is about convention over configuration. Of course it's possible to edit the resulting .java files and add any additional annotations desired if the defaults (as described at http://java.sun.com/javaee/6/docs/api/javax/persistence/DiscriminatorColumn.html) are unacceptable. In due course we'll also have Spring Shell separated out and provide text editing commands that can be incorporated into scripts, in the spirit of *nix tools like sed.
Note that if your @Entity has @MappedSuperclass, Hibernate throws a java.lang.AssertionError from AnnotationBinder.java:817 when executing with JDK 5+ assertions enabled. Because Maven (and "perform tests") executes with assertions enabled by default, the tests will fail in this case. However, they will pass by default in Eclipse as it defaults to not executing the assertions. You can see the failure in Eclipse by add the "-ea" JVM argument when invoking the tests within Eclipse. I do not consider there anything wrong with the code Roo produces given it complies with the @MappedSuperclass JavaDocs and executes fine with OpenJPA (as trying the above sample script reveals).
Any further comments on this are welcome.