Expand LSP snippet with omnifunc

[Supreeeme]

After searching for a solution to this for a while, I ended up implementing it myself. Here it is in its pure lua glory.

-- lspconfig portion
local caps = vim.lsp.protocol.make_client_capabilities()
caps.textDocument.completion.completionItem.snippetSupport = true

local function on_attach(client, bufnr)
    ...
    vim.opt_local.omnifunc = 'v:lua.vim.lsp.omnifunc'
end

-- later
require('lspconfig')[<server name>].setup{
    ...
    on_attach = on_attach,
    capabilities = caps
}

-- snippet expansion autocommand portion
vim.api.nvim_create_augroup("my-luasnip", {})
vim.api.nvim_create_autocmd('CompleteDone', {
	group = "my-luasnip",
	desc = "Expand LSP snippet",
	pattern = "*",
	callback = function(opts)
		local comp = vim.v.completed_item

		-- check that this is an lsp completion
		if not vim.tbl_get(comp, 'user_data', 'nvim', 'lsp') then return end

		-- check that we were given a snippet
		local complete_info = comp.user_data.nvim.lsp.completion_item
		if not complete_info.insertTextFormat or complete_info.insertTextFormat == 1 then return end

		-- remove the inserted text
		local start_col = complete_info.textEdit.range.start.character+1
		vim.fn.cursor(vim.fn.line('.'), start_col)
		vim.cmd.normal{args = {"d" .. #comp.word .. "l"}}

		-- if the inserted text was the last text on the line, the deletion command will leave the cursor 1 column left
		-- of where we need to insert the snippet (because insert mode can put the cursor 1 position ahead of the last column)
		-- move the cursor back over 1
		vim.fn.cursor(vim.fn.line('.'), start_col)

		-- insert snippet
		local snip_text = vim.tbl_get(complete_info, 'textEdit', 'newText') or comp.insertText
		assert(snip_text, "Language server indicated it had a snippet, but no snippet text could be found!")
		require('luasnip').lsp_expand(snip_text)
	end
})

[leiserfg]

Isn't it missing the step of actually populating the list? I mean, an implementation of omifunc is also required.

[Supreeeme]

Ah, thought there was a part I forgot. Luckily that's the easiest part :) I added it.