nvim-lspconfig omnifunc opens preview window

Question

Having configured nvim-lspconfig exactly as officially recommended, I want to use the completion functionality via omnifunc.

When pressing <C-X><C-O>, a drop down window appears right below my cursor position with options to select. On the other hand, another Window named Preview opens above my current buffer window with two empty lines. Is this intended, and if not, how can I fix it?

I feel like in this preview window should be a description and syntax information about various functions and packages. This problem arises with pyright (Python) as well as clangd (C++), so I suspect it is a neovim problem.

Answer 1

This happens when completeopt has the preview option in it. You probably added this to your config at one point.

Check verbose set completeopt? to see its contents and where it was last set from, so you can remove it from your config. If it's being set by a plugin and you want to explicitly disable it, use set completeopt-=preview.