Implement io.readClassResource and io.readClassLoaderResource

[armanbilge]

Addresses #2503.

[armanbilge]

Maybe this should be blocking 🤔

[mpilquist]

It might be nice to do this in a way which can use Files if the resource is a jar:file URL. We don't currently allow it because we have no way to construct a java.nio.file.Path via a URI.

BTW, we should also note that the resource path is absolute, not relative to a class. E.g., classOf[Foo].getResource("foo.properties") vs classOf[Foo].getClassLoader.getResource("a/b/c/foo.properties")

[armanbilge]

It might be nice to do this in a way which can use Files if the resource is a jar:file URL.

How would that work exactly? Do you mean use Files to implement this method? Or do you mean add a method to the Files API which works with a URL instead of Path?

For the former, I'm not sure if that's possible, since the file is embedded in the jar right? Seems like JavaURLConnection would be how to interact with those.

[mpilquist]

Yeah okay, I forgot that there's no default jar: file system handler. I wanted a way to do this without going through InputStream but I guess that's not possible.

[armanbilge]

Ohh, no I think I got you. Maybe this is possible, using FileSystems.newFileSystem? Would this actually make a difference?

[mpilquist]

Right, we'd have to call newFileSystem with a path to the JAR and then create a java.nio.file.Path from that file system for the resource in the JAR. And we'd likely still need a fallback to current implementation. Probably best to stick with what you've got -- the original fs2 InputStream integration seemed to have high overhead but I'm probably worried about an implementation that no longer exists.

[armanbilge]

H/t @Daenyth for the classtag trick.