Optional dependencies

[Reinier Zwitserloot]

Perhaps just 'optional module module.name;' ?

 --Reinier Zwitserloot

On Tue, Dec 1, 2015 at 9:48 PM, Paul Benedict <pbenedict at apache.org> wrote:

> There is certain irony in seeing "requires optional" :-) Two contradictory
> terms side-by-side.
>
> Cheers,
> Paul
>
> On Tue, Dec 1, 2015 at 2:40 PM, Rémi Forax <forax at univ-mlv.fr> wrote:
>
> > or simply
> >
> > module org.joda.time {
> >   requires optional module org.joda.convert;
> >   exports ...
> > }
> >
> > "optional" means present at compile time and optional at runtime.
> >
> > Rémi
> >
> >
> > Le 1 décembre 2015 16:49:52 CET, Stephen Colebourne <
> scolebourne at joda.org>
> > a écrit :
> > >On 1 December 2015 at 15:39, Alan Bateman <Alan.Bateman at oracle.com>
> > >wrote:
> > >> This should be doable but maybe not obvious. Can you say a bit more
> > >about
> > >> the Joda-Time optional dependency on Joda-Convert first? In
> > >particular, are
> > >> there static references to types in Joda-Convert and maybe a
> > >reflection
> > >> guard to check the presence of one of its types?
> > >>
> > >> It might be that you have to compile module joda.time with
> > >> -XaddReads:joda.time=joda.convert. At run-time then you can use
> > >Module
> > >> addReads to read module joda.convert when it's in the module graph.
> > >
> > >So, there are three variants of dependency in that list.
> > >
> > >1) Joda-Time depends on Joda-Convert solely for annotations. Thus, the
> > >annotations need to be available to compile against. The annotations
> > >have runtime scope, so must remain in the bytecode. However, only
> > >those users that want to use Joda-Convert in anger will ever care
> > >about them. For everyone else, the fact that there is no class file
> > >for the annotation at runtime is not a problem.
> > >
> > >2) The Joda-Convert dependency on Guava is reflection based. If it
> > >finds the class on the classpath it will enable the conversion logic.
> > >If it doesn't it won't.
> > >
> > >3) The ElSql dependency on Spring is not reflection based. If the user
> > >uses the class ElSqlBundle, they have to have Spring available. If
> > >they do not use that class, they do not have to have Spring available.
> > >
> > >The Joda-Beans dependencies are a mixture of the second and third
> > >type..
> > >
> > >
> > >I can see how the compile time flag could work, which is good.
> > >However, I think that it should be part of the module-info file, since
> > >the project cannot be compiled without it.
> > >
> > >module org.joda.time {
> > >  exports ...
> > >  at-compile-time {
> > >    requires module org.joda.convert;
> > >  }
> > >}
> > >
> > >Stephen
> >
> >
>