fix: auto insert breaking on single line text edit

closes #169

lua/blink/cmp/accept/preview.lua

@@ -1,5 +1,5 @@
 --- @param item blink.cmp.CompletionItem
-local function preview(item)
+local function preview(item, previous_text_edit)
   local text_edits_lib = require('blink.cmp.accept.text-edits')
   local text_edit = text_edits_lib.get_from_item(item)
 
@@ -9,6 +9,8 @@ local function preview(item)
     text_edit.newText = expanded_snippet and tostring(expanded_snippet) or text_edit.newText
   end
 
+  if previous_text_edit ~= nil then text_edit.range = text_edits_lib.get_undo_text_edit_range(previous_text_edit) end
+
   text_edits_lib.apply_text_edits(item.client_id, { text_edit })
   vim.api.nvim_win_set_cursor(0, {
     text_edit.range.start.line + 1,

lua/blink/cmp/accept/text-edits.lua

@@ -28,16 +28,16 @@ function text_edits.apply_text_edits(client_id, edits)
 end
 
 --- @param text_edit lsp.TextEdit
-function text_edits.undo_text_edit(text_edit)
+function text_edits.get_undo_text_edit_range(text_edit)
   text_edit = vim.deepcopy(text_edit)
   local lines = vim.split(text_edit.newText, '\n')
-  local range = text_edit.range
+  local last_line_len = lines[#lines] and #lines[#lines] or 0
 
+  local range = text_edit.range
   range['end'].line = range.start.line + #lines - 1
-  range['end'].character = lines[#lines] and #lines[#lines] or 0
-  text_edit.newText = ''
+  range['end'].character = #lines > 1 and last_line_len or range.start.character + last_line_len
 
-  vim.lsp.util.apply_text_edits({ text_edit }, vim.api.nvim_get_current_buf(), 'utf-16')
+  return range
 end
 
 --- @param item blink.cmp.CompletionItem

lua/blink/cmp/windows/autocomplete.lua

@@ -185,10 +185,9 @@ local function select(line, skip_auto_insert)
   -- when auto_insert is enabled, we immediately apply the text edit
   if config.windows.autocomplete.selection == 'auto_insert' and selected_item ~= nil and not skip_auto_insert then
     require('blink.cmp.trigger.completion').suppress_events_for_callback(function()
-      if autocomplete.preview_text_edit ~= nil and autocomplete.preview_context_id == autocomplete.context.id then
-        text_edits_lib.undo_text_edit(autocomplete.preview_text_edit)
-      end
-      autocomplete.preview_text_edit = require('blink.cmp.accept.preview')(selected_item)
+      if autocomplete.preview_context_id ~= autocomplete.context.id then autocomplete.preview_text_edit = nil end
+      autocomplete.preview_text_edit =
+        require('blink.cmp.accept.preview')(selected_item, autocomplete.preview_text_edit)
       autocomplete.preview_context_id = autocomplete.context.id
     end)
   end