fix(options): repair stale UI state after :set all& #39026

Problem: `set all&` resets option values directly and leaves UI-derived state stale for `guicursor`, `laststatus`, and `showtabline`.

Solution: Repair some of the stale UI state in the bulk reset path by reparsing `guicursor`, refreshing statusline state, and recomputing tabline/window rows.

src/nvim/option.c

@@ -1579,6 +1579,7 @@ int do_set(char *arg, int opt_flags)
           arg++;
           // Only for :set command set global value of local options.
           set_options_default(opt_flags);
+          didset_options_all();
           didset_options();
           didset_options2();
           ui_refresh_options();
@@ -1827,6 +1828,26 @@ static void didset_options2(void)
   tabstop_set(curbuf->b_p_vts,  &curbuf->b_p_vts_array);
 }
 
+/// Repair UI state after `:set all&`.
+///
+/// `set_options_default` resets option values via `set_option_default` and
+/// `set_option_direct` without invoking per-option `did_set` callbacks, so
+/// UI-derived state (cursor shape, statusline, tabline) can get out of sync.
+/// This function patches the known cases.
+///
+/// Note: We intentionally do not replay all `did_set` callbacks
+/// (`opt_did_set_cb`) because they have order-dependent side effects and
+/// old/new transition logic that does not hold when values are already reset.
+static void didset_options_all(void)
+{
+  const char *errmsg = parse_shape_opt(SHAPE_CURSOR);
+  assert(errmsg == NULL);
+  (void)errmsg;
+  last_status(false);
+  win_float_update_statusline();
+  win_new_screen_rows();
+}
+
 /// Check for string options that are NULL (normally only termcap options).
 void check_options(void)
 {

test/functional/ui/cursor_spec.lua

@@ -378,6 +378,22 @@ describe('ui/cursor', function()
     end)
   end)
 
+  it("'set all&' reapplies 'guicursor'", function()
+    command('set guicursor=n:ver25')
+    screen:expect(function()
+      eq('vertical', screen._mode_info[1].cursor_shape)
+      eq(25, screen._mode_info[1].cell_percentage)
+    end)
+
+    command('set all&')
+    screen:expect(function()
+      eq('block', screen._mode_info[1].cursor_shape)
+      eq(0, screen._mode_info[1].blinkon)
+      eq(0, screen._mode_info[1].blinkoff)
+      eq(true, screen._cursor_style_enabled)
+    end)
+  end)
+
   it(':sleep does not hide cursor when sleeping', function()
     n.feed(':sleep 300m | echo 42')
     screen:expect([[

test/functional/ui/options_spec.lua

@@ -172,6 +172,33 @@ describe('UI receives option updates', function()
     end)
   end)
 
+  it("restores statusline and tabline after 'set all&'", function()
+    reset()
+    command('tabnew | tabnew')
+    command('set laststatus=0 showtabline=0')
+    screen:expect({
+      unchanged = true,
+      condition = function()
+        local function row_text(row)
+          local chunks = {}
+          for _, cell in ipairs(screen._grid.rows[row]) do
+            table.insert(chunks, cell.text)
+          end
+          return table.concat(chunks)
+        end
+
+        eq(nil, row_text(1):find('%[No Name%]'))
+        eq(nil, row_text(screen._grid.height - 1):find('All', 1, true))
+      end,
+    })
+
+    command('set all&')
+    screen:expect({
+      unchanged = true,
+      any = { '[No Name]', 'All' },
+    })
+  end)
+
   it('with UI extensions', function()
     local expected = reset({ ext_cmdline = true, ext_wildmenu = true })