Rely always on workspace URI instead of Dir.pwd

[vinistock]

Motivation

Closes #2382

This PR stops using Dir.pwd and starts relying exclusively on the workspace URI provided by the client. Dir.pwd is not adequate because clients may spawn the language server in a directory that isn't the workspace. In addition to that, Dir.pwd may be a symlink, which can also cause issues in certain situations (as we received reports in the past).

Important note

There's one major caveat here. We are still unable to get rid of this usage of Dir.pwd when setting up the custom bundle.

The reason is because the way Bundler works is a bit incompatible with how language servers work and that prevents us from doing the right thing here. What the LSP spec dictates is that a language server should spawn and immediately respond to the initialize request.

However, for user convenience, we first setup the custom bundle, so that people don't have to add ruby-lsp to their Gemfiles. Ideally, we would

• Spawn the server
• Read the initialize request to get the workspace URI
• Then setup the custom bundle
• After a successful custom bundle setup, re-invoke Bundler.setup to organize the load paths as necessary
• And then respond back to the editor

Bundler doesn't allow you to invoke Bundler.setup twice. And even if we only invoke it once, we would not be able to require anything until the Bundler.setup call happens because that may lead to required gem version mismatches.

This is the reason why we setup the custom bundle and then replace the existing process with a bundle exec version of it.

Because of the process replacement thing, we cannot read the initialize request from STDIN while setting up the custom bundle or else the parameters for initialization would be completely lost after re-launching the process with bundle exec.

Finally, since we cannot read the request parameters during custom bundle initialization, we do not know what the workspace URI is.

My hope is to work more closely with the Bundler team and brainstorm some way that dependency setup can be better integrated into the way language servers work. That would not only improve the Dir.pwd thing, but it would allow us to display custom error messages depending on which failures happened during the custom bundle setup. For now, this is the best we can do.

Implementation

Started using the provided workspace URI everywhere and removed all Dir.pwd usages that aren't in tests.

Automated Tests

Adapted existing tests.

[st0012]

Since the workspace_path is the key information for the indexer and now requires external output, we should make it a required argument and change how RubyIndexer::Configuration is initialized, even if we simply pass Dir.pwd in the first and change it later.

[st0012]

I opened #2433 to change the way configuration is initialized.