Revert to previous partial symbol on autocomplete

This change handles issue reported on lite-xl/lite-xl-lsp#67
by restoring previous partial since the completion request is async
and new text could have been written while handling the LSP server
response, which results in invalid insert positions for the received
completion items.

Depends on pragtical/pragtical#66

init.lua

@@ -551,6 +551,16 @@ local function autocomplete_onselect(index, item)
   local dv = get_active_docview()
   if completion.textEdit then
     if dv then
+      -- Restore previous partial since the complete request is async and
+      -- new text could have been written while retrieving autocomplete items
+      -- which results in invalid insert positions if we don't revert partial
+      local current_partial = {autocomplete.get_partial_symbol()}
+      if current_partial[1] ~= item.data.partial[1] then
+        local partial, pl1, pc1, pl2, pc2 = table.unpack(current_partial)
+        dv.doc:remove(pl1, pc1, pl2, pc2)
+        partial, pl1, pc1 = table.unpack(item.data.partial)
+        dv.doc:insert(pl1, pc1, partial)
+      end
       local is_snippet = completion.insertTextFormat
         and completion.insertTextFormat == protocol.InsertTextFormat.Snippet
       local edit_applied = apply_edit(
@@ -587,8 +597,7 @@ local function autocomplete_onselect(index, item)
     ---@type core.doc
     local doc = dv.doc
     if dv then
-      local line2, col2 = doc:get_selection()
-      local line1, col1 = doc:position_offset(line2, col2, translate.start_of_word)
+      local _, line1, col1, line2, col2 = autocomplete.get_partial_symbol()
       doc:set_selection(line1, col1, line2, col2)
       snippets.execute {format = 'lsp', template = completion.insertText}
       return true
@@ -1402,6 +1411,8 @@ function lsp.request_completion(doc, line, col, forced)
         return false
       end
 
+      local partial = { autocomplete.get_partial_symbol() }
+
       server:push_request('textDocument/completion', {
         params = request,
         overwrite = true,
@@ -1511,7 +1522,9 @@ function lsp.request_completion(doc, line, col, forced)
               info = info,
               desc = desc,
               data = {
-                server = server, completion_item = symbol
+                server = server,
+                completion_item = symbol,
+                partial = partial
               },
               onselect = autocomplete_onselect
             }