vim-patch:9.1.0814: mapset() may remove unrelated mapping (#30941)

Problem:  mapset() may remove unrelated mapping whose {rhs} matches the
          restored mapping's {lhs}.
Solution: only match by {lhs} when unmapping for mapset() (zeertzjq).

closes: vim/vim#15935

https://github.com/vim/vim/commit/fdf135a0525746cc0ff85bed2fbbde320ddb6d0d

3 files changed, 37 insertions, 9 deletions

diff --git a/src/nvim/mapping.c b/src/nvim/mapping.c
index e055ebc2fa..23efd2a841 100644
--- a/src/nvim/mapping.c
+++ b/src/nvim/mapping.c
@@ -568,6 +568,12 @@ static int buf_do_map(int maptype, MapArguments *args, int mode, bool is_abbrev,
   mapblock_T **abbr_table = args->buffer ? &buf->b_first_abbr : &first_abbr;
   mapblock_T *mp_result[2] = { NULL, NULL };
 
+  bool unmap_lhs_only = false;
+  if (maptype == MAPTYPE_UNMAP_LHS) {
+    unmap_lhs_only = true;
+    maptype = MAPTYPE_UNMAP;
+  }
+
   // For ":noremap" don't remap, otherwise do remap.
   int noremap = args->script ? REMAP_SCRIPT
                              : maptype == MAPTYPE_NOREMAP ? REMAP_NONE : REMAP_YES;
@@ -720,8 +726,8 @@ static int buf_do_map(int maptype, MapArguments *args, int mode, bool is_abbrev,
     // entry with a matching 'to' part. This was done to allow ":ab foo bar"
     // to be unmapped by typing ":unab foo", where "foo" will be replaced by
     // "bar" because of the abbreviation.
-    for (int round = 0; (round == 0 || maptype == MAPTYPE_UNMAP) && round <= 1
-         && !did_it && !got_int; round++) {
+    const int num_rounds = maptype == MAPTYPE_UNMAP && !unmap_lhs_only ? 2 : 1;
+    for (int round = 0; round < num_rounds && !did_it && !got_int; round++) {
       int hash_start, hash_end;
       if ((round == 0 && has_lhs) || is_abbrev) {
         // just use one hash
@@ -935,9 +941,11 @@ theend:
 /// for :cabbr mode is MODE_CMDLINE
 /// ```
 ///
-/// @param maptype  MAPTYPE_MAP for |:map|
-///                 MAPTYPE_UNMAP for |:unmap|
-///                 MAPTYPE_NOREMAP for |:noremap|.
+/// @param maptype  MAPTYPE_MAP for |:map| or |:abbr|
+///                 MAPTYPE_UNMAP for |:unmap| or |:unabbr|
+///                 MAPTYPE_NOREMAP for |:noremap| or |:noreabbr|
+///                 MAPTYPE_UNMAP_LHS is like MAPTYPE_UNMAP, but doesn't try to match
+///                 with {rhs} if there is no match with {lhs}.
 /// @param arg      C-string containing the arguments of the map/abbrev
 ///                 command, i.e. everything except the initial `:[X][nore]map`.
 ///                 - Cannot be a read-only string; it will be modified.
@@ -2348,7 +2356,7 @@ void f_mapset(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   MapArguments unmap_args = MAP_ARGUMENTS_INIT;
   set_maparg_lhs_rhs(lhs, strlen(lhs), "", 0, LUA_NOREF, p_cpo, &unmap_args);
   unmap_args.buffer = buffer;
-  buf_do_map(MAPTYPE_UNMAP, &unmap_args, mode, is_abbr, curbuf);
+  buf_do_map(MAPTYPE_UNMAP_LHS, &unmap_args, mode, is_abbr, curbuf);
   xfree(unmap_args.rhs);
   xfree(unmap_args.orig_rhs);
 
diff --git a/src/nvim/mapping.h b/src/nvim/mapping.h
index b82117ea86..fc120b683c 100644
--- a/src/nvim/mapping.h
+++ b/src/nvim/mapping.h
@@ -19,9 +19,10 @@
 
 /// Used for the first argument of do_map()
 enum {
-  MAPTYPE_MAP     = 0,
-  MAPTYPE_UNMAP   = 1,
-  MAPTYPE_NOREMAP = 2,
+  MAPTYPE_MAP       = 0,
+  MAPTYPE_UNMAP     = 1,
+  MAPTYPE_NOREMAP   = 2,
+  MAPTYPE_UNMAP_LHS = 3,
 };
 
 /// Adjust chars in a language according to 'langmap' option.
diff --git a/test/old/testdir/test_map_functions.vim b/test/old/testdir/test_map_functions.vim
index 8f7c8bae76..5118063b36 100644
--- a/test/old/testdir/test_map_functions.vim
+++ b/test/old/testdir/test_map_functions.vim
@@ -527,6 +527,25 @@ func Test_map_restore_negative_sid()
   call delete('Xresult')
 endfunc
 
+" Check that restoring a mapping doesn't remove a mapping whose {rhs} matches
+" the restored mapping's {lhs}.
+func Test_map_restore_with_rhs_match_lhs()
+  nnoremap <F2> <F3>
+  nnoremap <F3> <F4>
+  call assert_equal('<F3>', maparg('<F2>', 'n'))
+  call assert_equal('<F4>', maparg('<F3>', 'n'))
+  let d = maparg('<F3>', 'n', v:false, v:true)
+  nunmap <F3>
+  call assert_equal('<F3>', maparg('<F2>', 'n'))
+  call assert_equal('', maparg('<F3>', 'n'))
+  call mapset(d)
+  call assert_equal('<F3>', maparg('<F2>', 'n'))
+  call assert_equal('<F4>', maparg('<F3>', 'n'))
+
+  nunmap <F2>
+  nunmap <F3>
+endfunc
+
 func Test_maplist()
   new
   func s:ClearMappingsAbbreviations()