Active buffer name renders poorly in bufferline.nvim when the buffer has LSP diagnostics

The highlight of the active buffer name (file name) changes based on the severity of LSP diagnostics in that buffer in akinsho/bufferline.nvim.

Currently, those colors do not match those of the colorscheme:

error error

warn warn

hint hint

info info

The logic that generates the corresponding highlight groups relies on the fg color of core LSP-related Neovim highlight groups such as DiagnosticError.

Those seem to inherit a default fg color from Neovim, although we link them in the colorscheme:

The default fg color is assigned by Neovim ~because the linked groups don't have any, due to the undercurl style of highlights provided by the colorscheme.~ _edit: this actually occurs regardless of the set attributes._

We could address this in the colorscheme by defining BufferLineErrorDiagnosticSelected, etc. manually, but IMO it is more sound to address this in the plugin, like I did in https://github.com/nvim-lualine/lualine.nvim/pull/836, because background colors are assigned dynamically based on the plugin's (Lua) config.

sainnhe / everforest

Active buffer name renders poorly in bufferline.nvim when the buffer has LSP diagnostics #121