Allow lsp functionality for out-of-project files clicked through to

[alexheretic]

Lots of languages store dependency sources outside of project directories. E.g. Rust/cargo stores them at something like `~/.cargo/registry/repo123/some-crate-1.0.0/src/.

As far as RLS is concerned it's able to provide hover, definition, documentHighlight etc functionality for these dependencies sources. However, atom-languageclient currently can't tell these have a relation to the project so don't send the server any requests.

To me it seems feasible that we record the uris returned by textDocument/definition responses, associated with the server that sent them. If these files are open, and not in any other project we consider them eligible as project files in this language server.

What do you guys think?

Downstream: rust-lang/atom-ide-rust#96

[alexheretic]

Hacking away the non-project filter we can see it working a little. The clicked through file here is in ~/.cargo outside the project but rls can provide some hover functionality.

[UziTech]

Development of atom-languageclient has officially moved to https://github.com/atom-ide-community/atom-languageclient 🎉

If this is still an issue please consider opening an issue on that repo.