Handle methods with Void return types properly

[jonahgraham]

The DAP part of LSP4J was being too strict and failing to parse response objects for methods with Void return type. With Java 17 (or some version since Java 11) turning on more strict reflection rules, the "An illegal reflective access operation has occurred" that used to be a warning is now an exception like "Failed making constructor 'java.lang.Void#Void()' accessible"

This change makes the code work and compatible with how LSP4J handles LSP Void return types.

Fixes #674

[jonahgraham]

@sebthom it would be very helpful if you can test your failing case in #674 with this fix. You can pick up a p2 repo here: https://download.eclipse.org/lsp4j/builds/jonah/dap_return_void/

[sebthom]

I somehow cannot use the update site, I am getting:

I get the same error if I try to use https://download.eclipse.org/lsp4j/updates/releases/0.17.0/ instead of https://download.eclipse.org/lsp4j/updates/releases/0.16.0/

Apparently as of lsp4j 0.17.0 the org.eclipse.xtext.xbase.lib plugin is not part of the update site anymore. Is that on purpose?

[cdietrich]

We do not package it https://github.com/eclipse/lsp4j/blob/main/releng/p2/category.xml you can consume it from the 2022-09 Or the Xtext 2.28 update site

https://download.eclipse.org/modeling/tmf/xtext/updates/releases/2.28.0/

[sebthom]

That's odd, I am seeing this:

Maybe it's a UI bug in the Target Editor.

[cdietrich]

https://github.com/eclipse/lsp4j/blob/2260c479d5e02a37db5d65af51291c060d183009/releng/lsp4j-feature/feature.xml#L35

[cdietrich]

There was some back and forth in tycho how to deal with imports , maybe thus it got packaged in 15

[sebthom]

@cdietrich I added the xtext update site and now it works. thanks!

@jonahgraham I can confirm, that the change of this PR works as expected. Thanks for the quick resolution!