How to use line_to_cursor in a function node?

[RobberFox]

I'm making a latex snippet for fractions and I need to use an external auto_fraction(str) function that operates over a string up to the cursor position:

s( { trig= "%S/", regTrig=true, wordTrig=false, snippetType="autosnippet", resolveExpandParams=function(_snip, line_to_cursor, matched, _captures) }, fmta([[\frac{<>}{<>}<>]],
{ f(function(args, snip, line_to_cursor) return auto_fraction(line_to_cursor) end, {}), i(1), i(2) }), { condition = function() return math() end})

How do I actually use line_to_cursor in the f() node?

[L3MON4D3]

Mhmm, that line_to_cursor argument you use in your functionNode does not actually exist :/
Assuming that you want to have the line up to the beginning of the snippet, you could do

	s({
		trig= "%S/",
		regTrig=true,
		wordTrig=false,
		snippetType="autosnippet"
	}, fmta([[
		\frac{<>}{<>}<>
	]], {
		f(function(args, snip, line_to_cursor)
			local snip_range_from, _ = snip.snippet:get_buf_position()
			local snip_line = snip_range_from[1]
			local snip_from_col = snip_range_from[2]
			local before_snip_str = vim.api.nvim_buf_get_text(0, snip_line, 0, snip_line, snip_from_col, {})
			return auto_fraction(before_snip_str)
		end, {}),
		i(1),
		i(2)
	}), {
		condition = function()
			return true
			-- return math()
		end
	})