strings.truncate can freeze when in a fast event/strings.strcharpart's fallback is used

[lazy-orb-weaver]

(I saw the no longer maintained sign, consider this for documentation purposes or something)

there's an oopsie in strings.strcharpart's fallback function. sub takes start and end positions, and not start and length like vim's strcharpart:

plenary.nvim/lua/plenary/strings.lua

Lines 42 to 45 in 74b06c6

	if vim.in_fast_event() then
	return str:sub(nchar + 1, charlen)
	end
	return vim.fn.strcharpart(str, nchar, charlen)

when this fallback function is used, the truncate function can get stuck in an infinite loop whenever the direction is positive and the string is long enough to be truncated. for example, this freezes in a fast state:

truncate("test string", 5, "...", 1)

to fix this, I think the fallback just needs to be: return str:sub(nchar + 1, nchar + charlen)