vim-patch:8.1.0552: saved last search pattern may not be restored

Problem:    Saved last search pattern may not be restored.
Solution:   Call restore_last_search_pattern().  Add a check for balancing
            saving and restoring the last search pattern.
01a060da74

src/nvim/ex_getln.c

@@ -423,6 +423,7 @@ static void may_do_incsearch_highlighting(int firstc, long count,
   char_u use_last_pat;
 
   // Parsing range may already set the last search pattern.
+  // NOTE: must call restore_last_search_pattern() before returning!
   save_last_search_pattern();
 
   if (!do_incsearch_highlighting(firstc, s, &skiplen, &patlen)) {
@@ -566,6 +567,7 @@ static int may_add_char_to_search(int firstc, int *c, incsearch_state_T *s)
   int skiplen, patlen;
 
   // Parsing range may already set the last search pattern.
+  // NOTE: must call restore_last_search_pattern() before returning!
   save_last_search_pattern();
 
   // Add a character from under the cursor for 'incsearch'
@@ -573,6 +575,7 @@ static int may_add_char_to_search(int firstc, int *c, incsearch_state_T *s)
     restore_last_search_pattern();
     return FAIL;
   }
+  restore_last_search_pattern();
 
   if (s->did_incsearch) {
     curwin->w_cursor = s->match_end;
@@ -1445,6 +1448,7 @@ static int may_do_command_line_next_incsearch(int firstc, long count,
   int skiplen, patlen;
 
   // Parsing range may already set the last search pattern.
+  // NOTE: must call restore_last_search_pattern() before returning!
   save_last_search_pattern();
 
   if (!do_incsearch_highlighting(firstc, s, &skiplen, &patlen)) {

src/nvim/search.c

@@ -99,6 +99,7 @@ static struct spat saved_spats[2];
 // copy of spats[RE_SEARCH], for keeping the search patterns while incremental
 // searching
 static struct spat  saved_last_search_spat;
+static int did_save_last_search_spat = 0;
 static int saved_last_idx = 0;
 static bool saved_no_hlsearch = false;
 
@@ -316,6 +317,12 @@ void free_search_patterns(void)
 /// cancelling incremental searching even if it's called inside user functions.
 void save_last_search_pattern(void)
 {
+  if (did_save_last_search_spat != 0) {
+    IEMSG("did_save_last_search_spat is not zero");
+  } else {
+    did_save_last_search_spat++;
+  }
+
   saved_last_search_spat = spats[RE_SEARCH];
   if (spats[RE_SEARCH].pat != NULL) {
     saved_last_search_spat.pat = vim_strsave(spats[RE_SEARCH].pat);
@@ -326,8 +333,15 @@ void save_last_search_pattern(void)
 
 void restore_last_search_pattern(void)
 {
+  if (did_save_last_search_spat != 1) {
+    IEMSG("did_save_last_search_spat is not one");
+    return;
+  }
+  did_save_last_search_spat--;
+
   xfree(spats[RE_SEARCH].pat);
   spats[RE_SEARCH] = saved_last_search_spat;
+  saved_last_search_spat.pat = NULL;
   set_vv_searchforward();
   last_idx = saved_last_idx;
   set_no_hlsearch(saved_no_hlsearch);