Neovim lua config: how to append to listchars?

Question

In a neovim init.lua config, I know that I can append to a string like so:

vim.opt.wildignore:append("*/node_modules/*,*/vendor/*,*/venv/*,*/.venv/*,*/target/*")

However, I'm getting errors with the following attempts to append extends:# to the default value of listchars:

vim.opt.listchars:append("extends:#")
vim.opt.listchars:append(",extends:#")
vim.opt.listchars:append({"extends:#"})
vim.opt.listchars:append({",extends:#"})
vim.opt.listchars = vim.opt.listchars + "extends:#"
vim.opt.listchars = vim.opt.listchars + ",extends:#"

I thought it was perhaps because it's a mapping, but this also failed:

vim.opt.listchars:append({extends = "#"})

EDIT: ^^ this now works on 0.5.1. See below.

I don't see an :extend() method, but tried it anyway and it also fails.

It accepts this as valid: vim.opt.listchars = "extends:#"

What am I doing wrong here?

Answer 1

The 'listchars' option is implemented as a Lua table (akin to a Dict in Vim, possibly more similar to an object in JavaScript), so what you need to only change the extends setting is:

vim.opt.listchars.extends = "#"

Or, also valid:

vim.opt.listchars["extends"] = "#"

Answer 2

As of nvim 0.5.1, on MacOS and Linux, it appears that the vim.opt.listchars:append in my original question now works, and for some reason setting the map values as in vim.opt.listchars.extends = "e" or vim.opt.listchars.tab = "t" no longer works.

vim.opt.listchars:append({ extends = "#" })
print(vim.inspect(vim.opt.listchars:get()))

Answer 3

Actual this works (from the official doc: https://neovim.io/doc/user/lua.html): vim.opt.listchars = { space = '_', tab = '>~' }

In my case I got to add (init.lua or outsourced file for global-lua-settings)

vim.opt.listchars = {eol = '↵'}   
vim.opt.list = true

Answer 4

You can use:
vim.opt.listchars:append({ eol = '↵' })
or vim.opt.listchars + { eol = '↵' } to append
and vim.opt.listchars:prepend({ eol = '↵' })
or vim.opt.listchars ^ { eol = '↵' } to prepend to nvim Option objects.

Source: https://neovim.io/doc/user/lua.html#vim.env