vim-patch:8.2.2804: setting buffer local mapping with mapset() changes global

Problem:    Setting buffer local mapping with mapset() changes global mapping.
Solution:   Only set the local mapping. (closes vim/vim#8143)
https://github.com/vim/vim/commit/7ba1e4d363164e32a93cceab64b42e8c6d89e9f3

2 files changed, 32 insertions, 13 deletions

diff --git a/src/nvim/mapping.c b/src/nvim/mapping.c
index 0bb397c748..ac81cbcb89 100644
--- a/src/nvim/mapping.c
+++ b/src/nvim/mapping.c
@@ -2171,23 +2171,21 @@ void f_mapset(typval_T *argvars, typval_T *rettv, FunPtr fptr)
     .silent = tv_dict_get_number(d, "silent") != 0,
     .nowait = tv_dict_get_number(d, "nowait") != 0,
   };
-
   scid_T sid = (scid_T)tv_dict_get_number(d, "sid");
   linenr_T lnum = (linenr_T)tv_dict_get_number(d, "lnum");
-
-  mapblock_T **map_table = maphash;
-  mapblock_T **abbr_table = &first_abbr;
-
-  if (tv_dict_get_number(d, "buffer") != 0) {
-    map_table = curbuf->b_maphash;
-    abbr_table = &curbuf->b_first_abbr;
-  }
+  bool buffer = tv_dict_get_number(d, "buffer") != 0;
   // mode from the dict is not used
 
+  mapblock_T **map_table = buffer ? curbuf->b_maphash : maphash;
+  mapblock_T **abbr_table = buffer ? &curbuf->b_first_abbr : &first_abbr;
+
   // Delete any existing mapping for this lhs and mode.
-  char_u *arg = vim_strsave((char_u *)lhs);
-  do_map(1, arg, mode, is_abbr);  // TODO: refactor this later
-  xfree(arg);
+  MapArguments unmap_args = MAP_ARGUMENTS_INIT;
+  set_maparg_lhs_rhs(lhs, strlen(lhs), rhs, strlen(rhs), LUA_NOREF, 0, &unmap_args);
+  unmap_args.buffer = buffer;
+  buf_do_map(1, &unmap_args, mode, false, curbuf);
+  xfree(unmap_args.rhs);
+  xfree(unmap_args.orig_rhs);
 
   if (lhsrawalt != NULL) {
     map_add(curbuf, map_table, abbr_table, (char_u *)lhsrawalt, &args, noremap, mode, is_abbr,
@@ -2219,7 +2217,7 @@ void f_mapcheck(typval_T *argvars, typval_T *rettv, FunPtr fptr)
 /// @param buffer  If true, make a buffer-local mapping for curbuf
 void add_map(char *lhs, char *rhs, int mode, bool buffer)
 {
-  MapArguments args = { 0 };
+  MapArguments args = MAP_ARGUMENTS_INIT;
   set_maparg_lhs_rhs(lhs, strlen(lhs), rhs, strlen(rhs), LUA_NOREF, 0, &args);
   args.buffer = buffer;
 
diff --git a/src/nvim/testdir/test_maparg.vim b/src/nvim/testdir/test_maparg.vim
index 6b69def374..0bade1df7f 100644
--- a/src/nvim/testdir/test_maparg.vim
+++ b/src/nvim/testdir/test_maparg.vim
@@ -253,6 +253,27 @@ func Check_ctrlb_map(d, check_alt)
   endif
 endfunc
 
+func Test_map_local()
+  nmap a global
+  nmap <buffer>a local
+
+  let prev_map_list = split(execute('nmap a'), "\n")
+  call assert_match('n\s*a\s*@local', prev_map_list[0])
+  call assert_match('n\s*a\s*global', prev_map_list[1])
+
+  let mapping = maparg('a', 'n', 0, 1)
+  call assert_equal(1, mapping.buffer)
+  let mapping.rhs = 'new_local'
+  call mapset('n', 0, mapping)
+
+  " Check that the global mapping is left untouched.
+  let map_list = split(execute('nmap a'), "\n")
+  call assert_match('n\s*a\s*@new_local', map_list[0])
+  call assert_match('n\s*a\s*global', map_list[1])
+
+  nunmap a
+endfunc
+
 func Test_map_restore()
   " Test restoring map with alternate keycode
   nmap <C-B> back