vim-patch:8.2.3992: wrong local-additions in the help with language mix

Problem:    Wrong local-additions in the help with language mix.
Solution:   Adjust how the local additions list is generated. (Hirohito
            Higashi, closes vim/vim#9464)

https://github.com/vim/vim/commit/0e2508d9e63e63414de2c06b3c8a446fdfe4470b

Co-authored-by: h-east <h.east.727@gmail.com>

2 files changed, 46 insertions, 22 deletions

diff --git a/src/nvim/help.c b/src/nvim/help.c
index cdd930203f..37d240e5c6 100644
--- a/src/nvim/help.c
+++ b/src/nvim/help.c
@@ -743,28 +743,26 @@ void fix_help_buffer(void)
             // If foo.abx is found use it instead of foo.txt in
             // the same directory.
             for (int i1 = 0; i1 < fcount; i1++) {
-              for (int i2 = 0; i2 < fcount; i2++) {
-                if (i1 == i2) {
-                  continue;
-                }
-                if (fnames[i1] == NULL || fnames[i2] == NULL) {
+              const char *const f1 = fnames[i1];
+              const char *const t1 = path_tail(f1);
+              const char *const e1 = strrchr(t1, '.');
+              if (path_fnamecmp(e1, ".txt") != 0
+                  && path_fnamecmp(e1, fname + 4) != 0) {
+                // Not .txt and not .abx, remove it.
+                XFREE_CLEAR(fnames[i1]);
+                continue;
+              }
+
+              for (int i2 = i1 + 1; i2 < fcount; i2++) {
+                const char *const f2 = fnames[i2];
+                if (f2 == NULL) {
                   continue;
                 }
-                const char *const f1 = fnames[i1];
-                const char *const f2 = fnames[i2];
-                const char *const t1 = path_tail(f1);
                 const char *const t2 = path_tail(f2);
-                const char *const e1 = strrchr(t1, '.');
                 const char *const e2 = strrchr(t2, '.');
                 if (e1 == NULL || e2 == NULL) {
                   continue;
                 }
-                if (path_fnamecmp(e1, ".txt") != 0
-                    && path_fnamecmp(e1, fname + 4) != 0) {
-                  // Not .txt and not .abx, remove it.
-                  XFREE_CLEAR(fnames[i1]);
-                  continue;
-                }
                 if (e1 - f1 != e2 - f2
                     || path_fnamencmp(f1, f2, (size_t)(e1 - f1)) != 0) {
                   continue;
diff --git a/src/nvim/testdir/test_help.vim b/src/nvim/testdir/test_help.vim
index 2ba30ce57f..b370a1e13e 100644
--- a/src/nvim/testdir/test_help.vim
+++ b/src/nvim/testdir/test_help.vim
@@ -96,16 +96,42 @@ func Test_help_local_additions()
   call writefile(['*mydoc-ext.txt* my extended awesome doc'], 'Xruntime/doc/mydoc-ext.txt')
   let rtp_save = &rtp
   set rtp+=./Xruntime
-  help
-  1
-  call search('mydoc.txt')
-  call assert_equal('|mydoc.txt| my awesome doc', getline('.'))
-  1
-  call search('mydoc-ext.txt')
-  call assert_equal('|mydoc-ext.txt| my extended awesome doc', getline('.'))
+  help local-additions
+  let lines = getline(line(".") + 1, search("^$") - 1)
+  call assert_equal([
+  \ '|mydoc-ext.txt| my extended awesome doc',
+  \ '|mydoc.txt| my awesome doc'
+  \ ], lines)
+  call delete('Xruntime/doc/mydoc-ext.txt')
+  close
+
+  call mkdir('Xruntime-ja/doc', 'p')
+  call writefile(["local-additions\thelp.jax\t/*local-additions*"], 'Xruntime-ja/doc/tags-ja')
+  call writefile(['*help.txt* This is jax file', '',
+  \ 'LOCAL ADDITIONS: *local-additions*', ''], 'Xruntime-ja/doc/help.jax')
+  call writefile(['*work.txt* This is jax file'], 'Xruntime-ja/doc/work.jax')
+  call writefile(['*work2.txt* This is jax file'], 'Xruntime-ja/doc/work2.jax')
+  set rtp+=./Xruntime-ja
+
+  help local-additions@en
+  let lines = getline(line(".") + 1, search("^$") - 1)
+  call assert_equal([
+  \ '|mydoc.txt| my awesome doc'
+  \ ], lines)
+  close
+
+  help local-additions@ja
+  let lines = getline(line(".") + 1, search("^$") - 1)
+  call assert_equal([
+  \ '|mydoc.txt| my awesome doc',
+  \ '|help.txt| This is jax file',
+  \ '|work.txt| This is jax file',
+  \ '|work2.txt| This is jax file',
+  \ ], lines)
   close
 
   call delete('Xruntime', 'rf')
+  call delete('Xruntime-ja', 'rf')
   let &rtp = rtp_save
 endfunc