vim-patch:9.0.1092: search error message doesn't show used pattern (#21518)

Problem:    Search error message doesn't show used pattern.
Solution:   Pass the actually used pattern to where the error message is
            given. (Rob Pilling, closes vim/vim#11742)

https://github.com/vim/vim/commit/e86190e7c1297da29d0fc2415fdeca5ecae8d2ba

Co-authored-by: Rob Pilling <robpilling@gmail.com>

4 files changed, 33 insertions, 14 deletions

diff --git a/src/nvim/ex_cmds.c b/src/nvim/ex_cmds.c
index 5eb5359e90..4167d1d182 100644
--- a/src/nvim/ex_cmds.c
+++ b/src/nvim/ex_cmds.c
@@ -1618,12 +1618,12 @@ static int check_writable(const char *fname)
 }
 #endif
 
-/// write current buffer to file 'eap->arg'
-/// if 'eap->append' is true, append to the file
+/// Write current buffer to file "eap->arg".
+/// If "eap->append" is true, append to the file.
 ///
-/// if *eap->arg == NUL write to current file
+/// If "*eap->arg == NUL" write to current file.
 ///
-/// @return  FAIL for failure, OK otherwise
+/// @return  FAIL for failure, OK otherwise.
 int do_write(exarg_T *eap)
 {
   int other;
@@ -3443,8 +3443,8 @@ static int do_sub(exarg_T *eap, proftime_T timeout, long cmdpreview_ns, handle_T
     return 0;
   }
 
-  if (search_regcomp((char_u *)pat, RE_SUBST, which_pat, (cmdpreview ? 0 : SEARCH_HIS),
-                     &regmatch) == FAIL) {
+  if (search_regcomp((char_u *)pat, NULL, RE_SUBST, which_pat,
+                     (cmdpreview ? 0 : SEARCH_HIS), &regmatch) == FAIL) {
     if (subflags.do_error) {
       emsg(_(e_invcmd));
     }
@@ -4398,7 +4398,9 @@ void ex_global(exarg_T *eap)
     }
   }
 
-  if (search_regcomp((char_u *)pat, RE_BOTH, which_pat, SEARCH_HIS, &regmatch) == FAIL) {
+  char_u *used_pat;
+  if (search_regcomp((char_u *)pat, &used_pat, RE_BOTH, which_pat,
+                     SEARCH_HIS, &regmatch) == FAIL) {
     emsg(_(e_invcmd));
     return;
   }
@@ -4429,9 +4431,9 @@ void ex_global(exarg_T *eap)
       msg(_(e_interr));
     } else if (ndone == 0) {
       if (type == 'v') {
-        smsg(_("Pattern found in every line: %s"), pat);
+        smsg(_("Pattern found in every line: %s"), used_pat);
       } else {
-        smsg(_("Pattern not found: %s"), pat);
+        smsg(_("Pattern not found: %s"), used_pat);
       }
     } else {
       global_exe(cmd);
diff --git a/src/nvim/search.c b/src/nvim/search.c
index 009e8b4e19..e49535f484 100644
--- a/src/nvim/search.c
+++ b/src/nvim/search.c
@@ -132,7 +132,8 @@ typedef struct SearchedFile {
 /// @param regmatch  return: pattern and ignore-case flag
 ///
 /// @return          FAIL if failed, OK otherwise.
-int search_regcomp(char_u *pat, int pat_save, int pat_use, int options, regmmatch_T *regmatch)
+int search_regcomp(char_u *pat, char_u **used_pat, int pat_save, int pat_use, int options,
+                   regmmatch_T *regmatch)
 {
   int magic;
   int i;
@@ -163,6 +164,10 @@ int search_regcomp(char_u *pat, int pat_save, int pat_use, int options, regmmatc
     add_to_history(HIST_SEARCH, (char *)pat, true, NUL);
   }
 
+  if (used_pat) {
+    *used_pat = pat;
+  }
+
   if (mr_pattern_alloced) {
     xfree(mr_pattern);
     mr_pattern_alloced = false;
@@ -509,7 +514,7 @@ void last_pat_prog(regmmatch_T *regmatch)
     return;
   }
   emsg_off++;           // So it doesn't beep if bad expr
-  (void)search_regcomp((char_u *)"", 0, last_idx, SEARCH_KEEP, regmatch);
+  (void)search_regcomp((char_u *)"", NULL, 0, last_idx, SEARCH_KEEP, regmatch);
   emsg_off--;
 }
 
@@ -567,7 +572,7 @@ int searchit(win_T *win, buf_T *buf, pos_T *pos, pos_T *end_pos, Direction dir,
     timed_out = &extra_arg->sa_timed_out;
   }
 
-  if (search_regcomp(pat, RE_SEARCH, pat_use,
+  if (search_regcomp(pat, NULL, RE_SEARCH, pat_use,
                      (options & (SEARCH_HIS + SEARCH_KEEP)), &regmatch) == FAIL) {
     if ((options & SEARCH_MSG) && !rc_did_emsg) {
       semsg(_("E383: Invalid search string: %s"), mr_pattern);
@@ -2523,7 +2528,7 @@ static int is_zero_width(char_u *pattern, int move, pos_T *cur, Direction direct
     pattern = (char_u *)spats[last_idx].pat;
   }
 
-  if (search_regcomp(pattern, RE_SEARCH, RE_SEARCH,
+  if (search_regcomp(pattern, NULL, RE_SEARCH, RE_SEARCH,
                      SEARCH_KEEP, &regmatch) == FAIL) {
     return -1;
   }
diff --git a/src/nvim/testdir/test_global.vim b/src/nvim/testdir/test_global.vim
index 8fb4ee0cfa..44a8784348 100644
--- a/src/nvim/testdir/test_global.vim
+++ b/src/nvim/testdir/test_global.vim
@@ -72,6 +72,18 @@ func Test_global_print()
   close!
 endfunc
 
+func Test_global_empty_pattern()
+  " populate history
+  silent g/hello/
+
+  redir @a
+  g//
+  redir END
+
+  call assert_match('Pattern not found: hello', @a)
+  "                                     ^~~~~ this was previously empty
+endfunc
+
 " Test for global command with newline character
 func Test_global_newline()
   new
diff --git a/test/unit/search_spec.lua b/test/unit/search_spec.lua
index ce37ebfc3a..be905bf5f0 100644
--- a/test/unit/search_spec.lua
+++ b/test/unit/search_spec.lua
@@ -37,7 +37,7 @@ end)
 describe('search_regcomp', function()
   local search_regcomp = function(pat, pat_save, pat_use, options )
     local regmatch = ffi.new("regmmatch_T")
-    local fail = search.search_regcomp(to_cstr(pat), pat_save, pat_use, options, regmatch)
+    local fail = search.search_regcomp(to_cstr(pat), nil, pat_save, pat_use, options, regmatch)
     return fail, regmatch
   end