:RustLsp renderDiagnostic floating window behavior

[rywng]

Feature description

Hello, I have two issues with the command:

1. In current implementation, running it again without arguments (:RustLsp renderDiagnostic) only cycles forward but not backwards, which is not really convenient and the functionality can be replaced by either nvim's built ins like vim.diagnostic.goto_next() and vim.diagnostic.goto_prev() or 3rd party plugins like :Telescope diagnostics. This is also talked about in Is it possible to cycle to prev instead of next? #599
2. If you run :RustLsp renderDiagnostic current, it shows up the diagnostic window with a option to "open in split", but running the command again wont focus on the window, and afaik there's now way to actually access the "open in split" menu:
   

For reference, in nvim's built in lsp commands, for example if you press K on a symbol, on the first time it would open up a popup:

and the second time you press it will focus the pop up and allow you to navigate inside the menu:

So I would suggest removing the cycle option, and enable users to focus the pop up menu when running the command twice, like many other lsp commands.

[mrcjkb]

Hey 👋

As you mentioned, your first issue is a duplicate of #599, so let's remove that from this issue and adjust the title.

Regarding your second issue:

The renderDiagnostic command uses vim.lsp.util.open_floating_preview, which is different from Neovim's hover windows (which is what you are referring to with "pressing K on a symbol").
You can use <C-w>w (ctrl+w+w) and Neovim's various other window navigation keymaps, (<C-w>h, <C-w>j, etc.) to navigate to the hover window.
Given the difference and the fact that you can navigate to the diagnostic window, I don't think implementing an equivalent to "pressing K twice" is really worth the added code complexity (but I'm open to being proven wrong via a PR 😄).

That being said, it's probably worth adding a <Plug> mapping, like the one for the hover action command.

I'll close this for now. Please feel free to open a PR if you would like the K+K-like behaviour, e.g. by running the command a second time, without any arguments.