fix(lsp): don't empty server start-boundary by next client response #37665

Problem:
Server start boundary can be emptied by response provided by next client.

Solution:
Don't empty it when extending the result list.

runtime/lua/vim/lsp/completion.lua

@@ -586,8 +586,8 @@ local function trigger(bufnr, clients, ctx)
       if result then
         Context.isIncomplete = Context.isIncomplete or result.isIncomplete
         local encoding = client and client.offset_encoding or 'utf-16'
-        local client_matches
-        client_matches, server_start_boundary = M._convert_results(
+        local client_matches, tmp_server_start_boundary
+        client_matches, tmp_server_start_boundary = M._convert_results(
           line,
           cursor_row - 1,
           cursor_col,
@@ -598,6 +598,7 @@ local function trigger(bufnr, clients, ctx)
           encoding
         )
 
+        server_start_boundary = tmp_server_start_boundary or server_start_boundary
         vim.list_extend(matches, client_matches)
       end
     end

test/functional/plugin/lsp/completion_spec.lua

@@ -1427,6 +1427,48 @@ describe('vim.lsp.completion: integration', function()
     eq({ 1, 17 }, n.api.nvim_win_get_cursor(0))
   end)
 
+  it('does not empty server start boundary', function()
+    local completion_list = {
+      isIncomplete = false,
+      items = {
+        {
+          label = 'div.foo',
+          insertTextFormat = 2,
+          textEdit = {
+            newText = '<div class="foo">$0</div>',
+            range = { start = { line = 0, character = 0 }, ['end'] = { line = 0, character = 7 } },
+          },
+        },
+      },
+    }
+    local completion_list2 = {
+      isIncomplete = false,
+      items = {
+        {
+          insertTextFormat = 1,
+          label = 'foo',
+        },
+      },
+    }
+    exec_lua(function()
+      vim.o.completeopt = 'menu,menuone,noinsert'
+    end)
+    create_server('dummy', completion_list)
+    create_server('dummy2', completion_list2)
+    feed('Adiv.foo<C-x><C-O>')
+    retry(nil, nil, function()
+      eq(
+        1,
+        exec_lua(function()
+          return vim.fn.pumvisible()
+        end)
+      )
+    end)
+    feed('<C-Y>')
+    eq('<div class="foo"></div>', n.api.nvim_get_current_line())
+    eq({ 1, 17 }, n.api.nvim_win_get_cursor(0))
+  end)
+
   it('sorts items when fuzzy is enabled and prefix not empty #33610', function()
     local completion_list = {
       isIncomplete = false,