Code review for jigsaw/jake -> jdk9/dev sync up

[Alan Bateman]

On 27/11/2016 11:15, Peter Levart wrote:
> Hi Alan,
>
> Overall this looks very good. I noticed a couple of nits...
Thanks for going through the changes.

> :
>
> So should Provider<S> rather declare the following?
>
>     Class<? extends S> type();
>
> Or alternatively, should ServiceLoader rather declare the following?
>
>     public Stream<? extends Provider<? extends S>> stream();
Well spotted, this should be Class<? extends S>. We could change the 
return of stream too but that might be more awkward to work with.

> :
>
> Now that there can be multiple parents of some configuration, those 
> parents can have common parents, but since you iterate the transitive 
> configurations of each individual parent in isolation, you can 
> encounter a common "diamond" configuration multiple times. Logically 
> all is well since you collect the required modules into Sets so 
> multiplicity is taken care of. But this is not very optimal from 
> algorithm point. It would be better to 1st make a stream of unique 
> configurations of all parents:
Fair comment, we haven't done any performance work for the multi parent 
scenario yet, mostly because #NonHierarchicalLayers is niche and there 
are still some open questions on how parents should be searched.

So we can change this as you suggest except that it regresses startup, 
this is the reason for skipping Configuration.empty(). However we 
support both so I'll get that change in so that the more elegant code is 
used when creating dynamic configurations.

-Alan