vim-patch:8.2.0902: using searchcount() in 'statusline' causes an error

Problem:    Using searchcount() in 'statusline' causes an error.
Solution:   Avoid saving/restoring the search patten recursively.
            (closes vim/vim#6194)
442a85369f

src/nvim/search.c

@@ -320,10 +320,9 @@ static bool saved_no_hlsearch = false;
 /// cancelling incremental searching even if it's called inside user functions.
 void save_last_search_pattern(void)
 {
-  if (did_save_last_search_spat != 0) {
+  if (++did_save_last_search_spat != 1) {
-    IEMSG("did_save_last_search_spat is not zero");
+    // nested call, nothing to do
-  } else {
+    return;
-    did_save_last_search_spat++;
   }
 
   saved_last_search_spat = spats[RE_SEARCH];
@@ -336,11 +335,15 @@ void save_last_search_pattern(void)
 
 void restore_last_search_pattern(void)
 {
-  if (did_save_last_search_spat != 1) {
+  if (--did_save_last_search_spat > 0) {
-    IEMSG("did_save_last_search_spat is not one");
+    // nested call, nothing to do
+    return;
+  }
+  if (did_save_last_search_spat != 0) {
+    iemsg("restore_last_search_pattern() called more often than"
+          " save_last_search_pattern()");
     return;
   }
-  did_save_last_search_spat--;
 
   xfree(spats[RE_SEARCH].pat);
   spats[RE_SEARCH] = saved_last_search_spat;

src/nvim/testdir/test_search_stat.vim

@@ -4,6 +4,8 @@
 " as test!
 
 source shared.vim
+source screendump.vim
+source check.vim
 
 func! Test_search_stat()
   new
@@ -164,3 +166,31 @@ func! Test_search_stat()
   set shortmess+=S
   bwipe!
 endfunc
+
+func Test_searchcount_in_statusline()
+  CheckScreendump
+
+  let lines =<< trim END
+    set shortmess-=S
+    call append(0, 'this is something')
+    function TestSearchCount() abort
+      let search_count = searchcount()
+      if !empty(search_count)
+	return '[' . search_count.current . '/' . search_count.total . ']'
+      else
+	return ''
+      endif
+    endfunction
+    set hlsearch
+    set laststatus=2 statusline+=%{TestSearchCount()}
+  END
+  call writefile(lines, 'Xsearchstatusline')
+  let buf = RunVimInTerminal('-S Xsearchstatusline', #{rows: 10})
+  call TermWait(buf)
+  call term_sendkeys(buf, "/something")
+  call VerifyScreenDump(buf, 'Test_searchstat_4', {})
+
+  call term_sendkeys(buf, "\<Esc>")
+  call StopVimInTerminal(buf)
+  call delete('Xsearchstatusline')
+endfunc