Add shadow plugin

[kyay10]

Fixes #23

The shadow plugin defaults seem to work just fine! It plays nicely with compileOnly and everything

[bnorm]

I don't think this quite fixes #23. We need to now make sure the shadowed jar is used as the compiler plugin artifact in the Gradle plugin. Last time I used tthe shadow Gradle plugin, it produced a secondary jar artifact rather than replacing the primary jar. Is that still the case or is the shadowing happing in the produced artifact?

[kyay10]

It worked for me experimentally (as in, I published to maven-local and applied my gradle plugin in a different project).
Looking at the docs, it seems like a little more config is needed, so I'll add it (strange that it worked without it for me).
Edit: running into some issues figuring out how to include sources and javadoc jars alongside the shadowed jar...
Edit 2: Okay, so it turns out that the shadow plugin wasn't doing anything in my setup. Yet, it seems that compiler plugin classpath is now transitive by default?? 😵‍💫.

[Mr3zee]

@kyay10 sorry to tag you here (and Brian also sorry for polluting the PR), but may I please ask you to check the internship emails? There is a time limit for scheduling interview and you may miss it, in which case we won't be able to proceed with the application this time. Thanks!

[bnorm]

Yet, it seems that compiler plugin classpath is now transitive by default?? 😵‍💫.

Not that I'm aware of. The compiler-plugin artifact just doesn't have any dependencies, there's only a compileOnly dependency on the compiler itself. So the shadow plugin should effectively produce the same result, since there's quite literally nothing to shadow.

It would make a good test, though, if we add a used dependency in the compiler-plugin artifact and make sure it works in a sample project.

[kyay10]

That's the thing, I've been testing with a plugin that has a dependency! I have a plugin that uses Arrow internally, and in ways that definitely require runtime usage (i.e. the uses aren't just inline), and it's working without neither shadowing nor any other workarounds to force transitivity!?! In fact, running the gradle dependencies task shows that, indeed, gradle pulled in Arrow as a dependency of the compiler-plugin in the XPluginClasspath configuration.

Regardless, I think the right approach here is shadowing. I just need to figure out how to get the sources and javadoc jars to be attached to components["shadow"]. I'll undraft the PR once I've figured that out.