vim-patch:9.1.1357: Vim incorrectly escapes tags with "[" in a help buffer

Problem:  Vim incorrectly escapes tags containing "[" in a help buffer
Solution: check if the buffer has the "help" filetype set, instead of
          already being a help buffer (Phạm Bình An)

fixes: vim/vim#17224
closes: vim/vim#17232

6af20a9be3

Co-authored-by: Phạm Bình An <phambinhanctb2004@gmail.com>
Co-authored-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: zeertzjq <zeertzjq@outlook.com>

src/nvim/normal.c

@@ -3500,7 +3500,7 @@ static void nv_ident(cmdarg_T *cap)
     } else if (cmdchar == '#') {
       aux_ptr = (magic_isset() ? "/?.*~[^$\\" : "/?^$\\");
     } else if (tag_cmd) {
-      if (curbuf->b_help) {
+      if (strcmp(curbuf->b_p_ft, "help") == 0) {
         // ":help" handles unescaped argument
         aux_ptr = "";
       } else {

test/old/testdir/test_help.vim

@@ -225,5 +225,22 @@ func Test_help_using_visual_match()
   call CheckScriptFailure(lines, 'E149:')
 endfunc
 
+func Test_helptag_navigation()
+  let helpdir = tempname()
+  let tempfile = helpdir . '/test.txt'
+  call mkdir(helpdir, 'pR')
+  call writefile(['', '*[tag*', '', '|[tag|'], tempfile)
+  exe 'helptags' helpdir
+  exe 'sp' tempfile
+  exe 'lcd' helpdir
+  setl ft=help
+  let &l:iskeyword='!-~,^*,^|,^",192-255'
+  call cursor(4, 2)
+  " Vim must not escape `[` when expanding the tag
+  exe "normal! \<C-]>"
+  call assert_equal(2, line('.'))
+  bw
+endfunc
+
 
 " vim: shiftwidth=2 sts=2 expandtab