vim-patch:8.2.2289: Vim9: 'cpo' can become empty (#19887)

Problem:    Vim9: 'cpo' can become empty.
Solution:   Use empty_option instead of an empty string.  Update quickfix
            buffer after restoring 'cpo'.  (closes vim/vim#7608)
https://github.com/vim/vim/commit/e5a2dc87fd9d63dfd0d9c379e363ee8b8c05b14c

Omit test as it is Vim9 script.

1 files changed, 13 insertions, 2 deletions

diff --git a/src/nvim/quickfix.c b/src/nvim/quickfix.c
index 17fbbe17b8..86054b50c6 100644
--- a/src/nvim/quickfix.c
+++ b/src/nvim/quickfix.c
@@ -7062,6 +7062,7 @@ void ex_helpgrep(exarg_T *eap)
     }
   }
 
+  bool updated = false;
   // Make 'cpoptions' empty, the 'l' flag should not be used here.
   char *const save_cpo = p_cpo;
   p_cpo = (char *)empty_option;
@@ -7092,16 +7093,26 @@ void ex_helpgrep(exarg_T *eap)
     qfl->qf_ptr = qfl->qf_start;
     qfl->qf_index = 1;
     qf_list_changed(qfl);
-    qf_update_buffer(qi, NULL);
+    updated = true;
   }
 
   if ((char_u *)p_cpo == empty_option) {
     p_cpo = save_cpo;
   } else {
-    // Darn, some plugin changed the value.
+    // Darn, some plugin changed the value.  If it's still empty it was
+    // changed and restored, need to restore in the complicated way.
+    if (*p_cpo == NUL) {
+      set_option_value("cpo", 0L, save_cpo, 0);
+    }
     free_string_option((char_u *)save_cpo);
   }
 
+  if (updated) {
+    // This may open a window and source scripts, do this after 'cpo' was
+    // restored.
+    qf_update_buffer(qi, NULL);
+  }
+
   if (au_name != NULL) {
     apply_autocmds(EVENT_QUICKFIXCMDPOST, au_name, curbuf->b_fname, true, curbuf);
     // When adding a location list to an existing location list stack,