David M. Lloyd
david.lloyd at redhat.com
Wed Apr 5 00:32:03 UTC 2017
On 04/04/2017 07:08 PM, mark.reinhold at oracle.com wrote:
> 2017/4/4 5:43:42 -0700, Brian Fox <brianf at infinity.nu>:
>> The Module-Name was enough of a hook to allow us to have Maven "fix" this
>> problem automatically by inserting a name based on the coordinates. Taking
>> that away I think again ties our hands.
> Yes. That's precisely the point.
> This isn't a "problem" for Maven to "fix".
> The final, explicit name of a module should be chosen by its author.
> It's not appropriate for a build tool or an artifact repository to
> enforce any particular convention for naming modules.
This is deceptive. Yes, build tools or repositories shouldn't enforce
conventions for naming. But at the same time, it's unrealistic to
expect that module authors are going to bundle module descriptors that
are universally compatible, and while naming is a part of this, it also
extends to things like dependency names and export types. All you need
is two modules which provide the same specification API in different
ways to expose this as truth, but the mere existence of Maven's
dependencyManagement and exclusions also are strong indicators. OSGi
can get away with library developers shipping descriptors, sometimes,
but this is generally a consequence of dependencies being expressed by
package instead of by bundle name, as well as other key differences
between the descriptor types.
I think rather what we'll end up with in the end is that non-trivial
application builders who want to use Jigsaw will rely almost exclusively
on build tooling to generate or regenerate "real" descriptors "safely"
for their application distributions, which in turn will be based on
meta-information from the artifacts being assembled and their build
descriptions. The build system has much more capability (and leisure)
than the run time to analyze the artifact graph to produce a cohesive
module structure and useful diagnostics.
There are a lot of little reasons why this kind of tooling is really the
only way users will be able be sure that their assembly of modules is
internally cohesive and consistent. The module descriptor is
fundamentally a different concern from the ABI and behavioral contracts
of software. I think that in this light, the entire concept of
automatic modules is questionable because with such tooling, automatic
modules give you nothing of value over adding a couple lines of XML to
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