feat: add function for custom folds

[fecet]

I think it would be great to make cells to be foldable 👀

fold:

Here is the setup for ufo(I note you also use this) https://github.com/fecet/nvim/blob/main/lua/modules/configs/editor/ufo.lua:

return function()
	local ufo = require("ufo")
	vim.o.fillchars = [[eob: ,fold: ,foldopen:,foldsep: ,foldclose:]]
	vim.o.foldcolumn = "1" -- '0' is not bad
	vim.o.foldlevel = 99 -- Using ufo provider need a large value, feel free to decrease the value
	vim.o.foldlevelstart = 99
	vim.o.foldenable = true

	local function get_cell_folds(bufnr)
		local function handleFallbackException(err, providerName)
			if type(err) == "string" and err:match("UfoFallbackException") then
				return ufo.getFolds(bufnr, providerName)
			else
				return require("promise").reject(err)
			end
		end
		return ufo.getFolds(bufnr, "lsp")
			:catch(function(err)
				return handleFallbackException(err, "treesitter")
			end)
			:catch(function(err)
				return handleFallbackException(err, "indent")
			end)
			:thenCall(function(ufo_folds)
				local ok, jupynium = pcall(require, "jupynium")
				if ok then
					for _, fold in ipairs(jupynium.get_folds()) do
						table.insert(ufo_folds, fold)
					end
				end
				return ufo_folds
			end)
	end

	local ftMap = {
		python = get_cell_folds,
	}

	ufo.setup({
		provider_selector = function(bufnr, filetype, buftype)
			return ftMap[filetype]
		end,
	})
end

[kiyoon]

I haven't tested this yet, but this looks good!

Is there any reason you set it as a draft?

[fecet]

Given that this PR using cells.line_types_entire_buf(), there may be some performance concerns. For example, the default setting allow jupynium to be loaded for any python file, so this will scan entire buffer every edit for regular python file. To preempt any potentially disruptive changes (like line_types become a cached property), I set it to draft for now.

Additionally, the current implementation requires extra configurations in the UFO, which can be cumbersome. I'm seeking suggestions for a more streamlined way to offer this feature

[fecet]

Is there any method to know wheter jupynium is start like require("jupynvim").is_start(), I tried require("jupynvim.highlighter").is_enabled() but it seems wasn't I want. Otherwise one should setup ufo like

			:thenCall(function(ufo_folds)
				local filename = vim.api.nvim_buf_get_name(bufnr)
				local ok, jupynium = pcall(require, "jupynium")
				if ok and string.match(filename, "%.ju.py$") then
					for _, fold in ipairs(jupynium.get_folds()) do
						table.insert(ufo_folds, fold)
					end
				end
				return ufo_folds

[kiyoon]

In highlighter.lua, I also match the file name. To be consistent with your settings, you can use this condition.

jupynium.nvim/lua/jupynium/highlighter.lua

Line 131 in 05ef99a

if utils.list_wildcard_match(vim.fn.expand "%", options.opts.jupynium_file_pattern) then

[kiyoon]

I just confirmed that it works very well. Can you mention this feature in README? It doesn't have to be long.

1. Mention the feature and the function get_folds
2. Mention that you can use plugins like nvim-ufo
3. Refer to this PR, for an example setup. Don't write too long code in the README. Or maybe write the code in the README but make it expandable (click to see the code)
4. Edit your main description of this PR to include the setup code, along with the link.

I think this much would be enough. Thanks a lot for your contribution!

[fecet]

Sure, will do it later

[kiyoon]

Thanks again for your contribution!