lsp: modify snippet-insertion-behaviour.

Explained in one of the comments, essentially we want the
snippetTextEdits to be visited one after the other, beginning with the
first.
This is not the default-behaviour, and thus needs some extra work.

Author: L3MON4D3

lua/luasnip/extras/lsp.lua

@@ -1,8 +1,33 @@
 local luasnip_ns_id = require("luasnip.session").ns_id
 local ls = require("luasnip")
+local session = ls.session
+local log = require("luasnip.util.log").new("lsp")
+local util = require("luasnip.util.util")
 
 local M = {}
 
+-- copied from init.lua, maybe find some better way to get it.
+local function _jump_into_default(snippet)
+	local current_buf = vim.api.nvim_get_current_buf()
+	if session.current_nodes[current_buf] then
+		local current_node = session.current_nodes[current_buf]
+		if current_node.pos > 0 then
+			-- snippet is nested, notify current insertNode about expansion.
+			current_node.inner_active = true
+		else
+			-- snippet was expanded behind a previously active one, leave the i(0)
+			-- properly (and remove the snippet on error).
+			local ok, err = pcall(current_node.input_leave, current_node)
+			if not ok then
+				log.warn("Error while leaving snippet: ", err)
+				current_node.parent.snippet:remove_from_jumplist()
+			end
+		end
+	end
+
+	return util.no_region_check_wrap(snippet.jump_into, snippet, 1)
+end
+
 ---Apply text/snippetTextEdits (at most one snippetText though).
 ---@param snippet_or_text_edits `(snippetTextEdit|textEdit)[]`
 --- snippetTextEdit as defined in https://github.com/rust-lang/rust-analyzer/blob/master/docs/dev/lsp-extensions.md#snippet-textedit)
@@ -13,28 +38,27 @@ local M = {}
 function M.apply_text_edits(snippet_or_text_edits, bufnr, offset_encoding, apply_text_edits_fn)
 	-- plain textEdits, applied using via `apply_text_edits_fn`.
 	local text_edits = {}
-	-- contains keys
+
+	-- list of snippet-parameters. These contain keys
 	--  - snippet (parsed snippet)
 	--  - mark (extmark, textrange replaced by the snippet)
-	local snippet_params
+	local all_snippet_params = {}
 
 	for _, v in ipairs(snippet_or_text_edits) do
 		if v.newText and v.insertTextFormat == 2 then
-			assert(snippet_params == nil, "Only one snippetTextEdit may be applied at once.")
-
 			-- from vim.lsp.apply_text_edits.
 			local start_row = v.range.start.line
 			local start_col = vim.lsp.util._get_line_byte_from_position(bufnr, v.range.start, offset_encoding)
 			local end_row = v.range['end'].line
 			local end_col = vim.lsp.util._get_line_byte_from_position(bufnr, v.range['end'], offset_encoding)
 
-			snippet_params = {
+			table.insert(all_snippet_params, {
 				snippet_body = v.newText,
 				mark = vim.api.nvim_buf_set_extmark(bufnr, luasnip_ns_id, start_row, start_col, {
 					end_row = end_row,
 					end_col = end_col
 				}),
-			}
+			})
 		else
 			table.insert(text_edits, v)
 		end
@@ -43,21 +67,63 @@ function M.apply_text_edits(snippet_or_text_edits, bufnr, offset_encoding, apply
 	-- first apply regular textEdits...
 	apply_text_edits_fn(text_edits, bufnr, offset_encoding)
 
-	-- ...then the snippet.
-	local mark_info = vim.api.nvim_buf_get_extmark_by_id(bufnr, luasnip_ns_id, snippet_params.mark, {details = true})
-	local mark_begin_pos = {mark_info[1], mark_info[2]}
-	local mark_end_pos = {mark_info[3].end_row, mark_info[3].end_col}
-
-	-- luasnip can only expand snippets in the active buffer, so switch (nop if
-	-- buf already active).
-	vim.api.nvim_set_current_buf(bufnr)
-	ls.lsp_expand(snippet_params.snippet_body, {
-		pos = mark_begin_pos,
-		clear_region = {
-			from = mark_begin_pos,
-			to = mark_end_pos,
-		},
-	})
+	-- ...then the snippetTextEdits.
+
+	-- store expanded snippets, if there are multiple we need to properly chain them together.
+	local expanded_snippets = {}
+	for i, snippet_params in ipairs(all_snippet_params) do
+		local mark_info = vim.api.nvim_buf_get_extmark_by_id(bufnr, luasnip_ns_id, snippet_params.mark, {details = true})
+		local mark_begin_pos = {mark_info[1], mark_info[2]}
+		local mark_end_pos = {mark_info[3].end_row, mark_info[3].end_col}
+
+		-- luasnip can only expand snippets in the active buffer, so switch (nop if
+		-- buf already active).
+		vim.api.nvim_set_current_buf(bufnr)
+
+		-- use expand_opts to chain snippets behind each other and store the
+		-- expanded snippets.
+		-- With the regular expand_opts, we will immediately jump into the
+		-- first snippet, if it contains an i(1), the following snippets will
+		-- belong inside it, which we don't want here: we want the i(0) of a
+		-- snippet to lead to the next (also skipping the i(-1)).
+		-- Even worse: by default, we would jump into the snippets during
+		-- snip_expand, which should only happen for the first, the later
+		-- snippets should be reached by jumping through the previous ones.
+		local expand_opts = {
+			pos = mark_begin_pos,
+			clear_region = {
+				from = mark_begin_pos,
+				to = mark_end_pos,
+			},
+		}
+
+		if i == 1 then
+			-- for first snippet: jump into it, and store the expanded snippet.
+			expand_opts.jump_into_func = function(snip)
+				expanded_snippets[i] = snip
+				local cr = _jump_into_default(snip)
+				print(cr)
+				return cr
+			end
+		else
+			-- don't jump into the snippet, just store it.
+			expand_opts.jump_into_func = function(snip)
+				expanded_snippets[i] = snip
+
+				print(session.current_nodes[bufnr])
+
+				-- let the already-active node stay active.
+				return session.current_nodes[bufnr]
+			end
+			-- jump from previous i0 directly into this snippet (ignore start_node).
+			expand_opts.jumplist_insert_func = function(snippet, _, _, _)
+					snippet.prev = expanded_snippets[i-1].insert_nodes[0]
+					expanded_snippets[i-1].insert_nodes[0].next = snippet
+			end
+		end
+
+		ls.lsp_expand(snippet_params.snippet_body, expand_opts)
+	end
 end
 
 function M.update_capabilities(capabilities)