Handling Whitespace in Neovim

List mode

In list mode Neovim can display whitespace using characters of your choosing. The characters to set for the different whitespace types can be found with :help listchars.

We will be setting all tabs to display as a double right angle » (U+00BB) and all leading and trailing spaces with a bullet • (U+2022). In your init.lua add the following to enable list mode at startup of Neovim.

vim.o.list = true
vim.o.listchars = 'tab:» ,lead:•,trail:•'

Note the space after the tab double right angle. The tab character must have a minimum of 2 characters and up to 3 characters can be used. Take a look at symbl.cc if you want to experiment with different characters.

Highlighting trailing whitespace

Highlighting trailing whitespace can come in handy if you don't have a linter setup to catch it for you. To do so we need to create our own Highlight group. After doing so we need to create a match for the Highlight group.

vim.api.nvim_set_hl(0, 'TrailingWhitespace', { bg='LightRed' })
vim.api.nvim_create_autocmd('BufEnter', {
	pattern = '*',
	command = [[
		syntax clear TrailingWhitespace |
		syntax match TrailingWhitespace "\_s\+$"
	]]}
)

Let's break down what is going on here. We use vim.api.nvim_set_hl() to create a Highlight group called TrailingWhitespace and set the background color to light red. You can also set the foreground color with fg='Color'. To get a list of color names see :help gui-colors.

Next we create an autocmd. If you are unfamiliar with autocmds all they do is allow you to run some commands when a certain event occurs. See :help autocmd-events for a list of events.

In our example, when the event BufEnter occurs on any file (pattern = '*') we clear all matches for the TrailingWhitespace group and then create a single match for the trailing whitespace with "\_s\+$". Note that we use the \_ modifier in our match so that the newline is matched as well. See :help \_x and :help perl-patterns for more info.