vim-patch:8.0.1208: 'statusline' drops empty group with highlight change

Problem:    'statusline' drops empty group with highlight change.
Solution:   Do not drop an empty group if it changes highlighting. (Marius
            Gedminas, closes vim/vim#2228)
6b89dbb55f

src/nvim/buffer.c

@@ -3480,15 +3480,25 @@ int build_stl_str_hl(
       //       Otherwise there would be no reason to do this step.
       if (curitem > groupitems[groupdepth] + 1
           && items[groupitems[groupdepth]].minwid == 0) {
-        bool has_normal_items = false;
+        // remove group if all items are empty and highlight group
-        for (long n = groupitems[groupdepth] + 1; n < curitem; n++) {
+        // doesn't change
-          if (items[n].type == Normal || items[n].type == Highlight) {
+        int group_start_userhl = 0;
-            has_normal_items = true;
+        int group_end_userhl = 0;
-            break;
+        int n;
+        for (n = 0; n < groupitems[groupdepth]; n++) {
+          if (items[n].type == Highlight) {
+            group_start_userhl = items[n].minwid;
           }
         }
-
+        for (n = groupitems[groupdepth] + 1; n < curitem; n++) {
-        if (!has_normal_items) {
+          if (items[n].type == Normal) {
+            break;
+          }
+          if (items[n].type == Highlight) {
+            group_end_userhl = items[n].minwid;
+          }
+        }
+        if (n == curitem && group_start_userhl == group_end_userhl) {
           out_p = t;
           group_len = 0;
         }

src/nvim/testdir/test_statusline.vim

@@ -5,7 +5,6 @@
 "   %N
 "   %T
 "   %X
-"   %*
 
 source view_util.vim
 
@@ -249,6 +248,70 @@ func Test_statusline()
   call assert_equal(sa1, sa3)
   call assert_notequal(sa1, sa2)
 
+  " An empty group that contains highlight changes
+  let g:a = ''
+  set statusline=ab%(cd%1*%{g:a}%*%)de
+  call assert_match('^abde\s*$', s:get_statusline())
+  let sa1=screenattr(&lines - 1, 1)
+  let sa2=screenattr(&lines - 1, 4)
+  call assert_equal(sa1, sa2)
+  let g:a = 'X'
+  call assert_match('^abcdXde\s*$', s:get_statusline())
+  let sa1=screenattr(&lines - 1, 1)
+  let sa2=screenattr(&lines - 1, 5)
+  let sa3=screenattr(&lines - 1, 7)
+  call assert_equal(sa1, sa3)
+  call assert_notequal(sa1, sa2)
+
+  let g:a = ''
+  set statusline=ab%1*%(cd%*%{g:a}%1*%)de
+  call assert_match('^abde\s*$', s:get_statusline())
+  let sa1=screenattr(&lines - 1, 1)
+  let sa2=screenattr(&lines - 1, 4)
+  call assert_notequal(sa1, sa2)
+  let g:a = 'X'
+  call assert_match('^abcdXde\s*$', s:get_statusline())
+  let sa1=screenattr(&lines - 1, 1)
+  let sa2=screenattr(&lines - 1, 3)
+  let sa3=screenattr(&lines - 1, 5)
+  let sa4=screenattr(&lines - 1, 7)
+  call assert_notequal(sa1, sa2)
+  call assert_equal(sa1, sa3)
+  call assert_equal(sa2, sa4)
+
+  " An empty group that contains highlight changes and doesn't reset them
+  let g:a = ''
+  set statusline=ab%(cd%1*%{g:a}%)de
+  call assert_match('^abcdde\s*$', s:get_statusline())
+  let sa1=screenattr(&lines - 1, 1)
+  let sa2=screenattr(&lines - 1, 5)
+  call assert_notequal(sa1, sa2)
+  let g:a = 'X'
+  call assert_match('^abcdXde\s*$', s:get_statusline())
+  let sa1=screenattr(&lines - 1, 1)
+  let sa2=screenattr(&lines - 1, 5)
+  let sa3=screenattr(&lines - 1, 7)
+  call assert_notequal(sa1, sa2)
+  call assert_equal(sa2, sa3)
+
+  let g:a = ''
+  set statusline=ab%1*%(cd%*%{g:a}%)de
+  call assert_match('^abcdde\s*$', s:get_statusline())
+  let sa1=screenattr(&lines - 1, 1)
+  let sa2=screenattr(&lines - 1, 3)
+  let sa3=screenattr(&lines - 1, 5)
+  call assert_notequal(sa1, sa2)
+  call assert_equal(sa1, sa3)
+  let g:a = 'X'
+  call assert_match('^abcdXde\s*$', s:get_statusline())
+  let sa1=screenattr(&lines - 1, 1)
+  let sa2=screenattr(&lines - 1, 3)
+  let sa3=screenattr(&lines - 1, 5)
+  let sa4=screenattr(&lines - 1, 7)
+  call assert_notequal(sa1, sa2)
+  call assert_equal(sa1, sa3)
+  call assert_equal(sa1, sa4)
+
   " %%: a percent sign.
   set statusline=10%%
   call assert_match('^10%\s*$', s:get_statusline())