`requires static` versus service binding

[David Lloyd]

On Fri, Jan 10, 2025 at 11:22 AM Magnus Ihse Bursie <
magnus.ihse.bursie at oracle.com> wrote:

> On 2025-01-08 22:33, David Lloyd wrote:
>
> Thus I'm inclined to believe that this restriction does not serve any
> practical benefit, and I hope it can be reconsidered to be respecified as
> a compile-time-only check.
>
> I agree. I was bitten by this as a Java developer in a hobby open source
> project, and even if at some point I understood why things where the way
> they are, I do not remember the reasoning, and I still find it confusing
> that it did not work as I expected it to, nor what steps I were supposed to
> take instead to resolve the problem at hand.
>
> I understand that this is not a very common problem or a high-priority
> issue, and I would have accepted that it was down-prioritized to the point
> that it will take a long time to resolve, but the current "works as
> intended" approach is still a bit hard for me to swallow.
>
I think there's a bit of self-selection: this kind of problem mostly
appears in more complex systems; the work to move complex systems to JPMS
is already nonzero; complex systems do not move because of this kind of
problem; therefore, the problem is considered a non-issue because nobody is
complaining about it.

As an experimental workaround I was trimming optional dependencies from the
descriptor at run time and doing a late `addReads` instead if the
dependency is present. This part works fine, however I then also have to
strip out `uses` and sometimes `provides` for this to work if they
correspond to packages in the optional dependency (which is a check that
also incurs a run time cost), and adding those back to the module late
requires hacky workarounds: for `addUses` I have to generate a class into
the target module so that it can call `Module.addUses` on my behalf, and
for `addProvides`, I have to access private JDK internals thus requiring
`--add-exports` of a core JDK package, which is less than ideal. I did
propose a patch to allow controllers to add these but it was soundly
rejected and the ensuing discussion yielded little of value. So hopefully
we can get around it another way: by allowing `uses` and `provides` of
services whose packages are not present at run time.

-- 
- DML • he/him
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