vim-patch:9.1.0642: Check that mapping rhs starts with lhs fails if not simplified (#29909)

Problem:  Check that mapping rhs starts with lhs doesn't work if lhs is
          not simplified.
Solution: Keep track of the mapblock containing the alternative lhs and
          also compare with it (zeertzjq).

fixes: vim/vim#15376
closes: vim/vim#15384

https://github.com/vim/vim/commit/9d997addc7bd0fd132a809cf497ed816e61fcd25

Cherry-pick removal of save_m_str from patch 8.2.4059.

3 files changed, 60 insertions, 38 deletions

diff --git a/src/nvim/getchar.c b/src/nvim/getchar.c
index a73824bdf5..6e441757dc 100644
--- a/src/nvim/getchar.c
+++ b/src/nvim/getchar.c
@@ -2341,8 +2341,7 @@ static int handle_mapping(int *keylenp, const bool *timedout, int *mapdepth)
     const int save_m_noremap = mp->m_noremap;
     const bool save_m_silent = mp->m_silent;
     char *save_m_keys = NULL;  // only saved when needed
-    char *save_m_str = NULL;  // only saved when needed
-    const LuaRef save_m_luaref = mp->m_luaref;
+    char *save_alt_m_keys = NULL;  // only saved when needed
 
     // Handle ":map <expr>": evaluate the {rhs} as an
     // expression.  Also save and restore the command line
@@ -2356,9 +2355,7 @@ static int handle_mapping(int *keylenp, const bool *timedout, int *mapdepth)
       may_garbage_collect = false;
 
       save_m_keys = xstrdup(mp->m_keys);
-      if (save_m_luaref == LUA_NOREF) {
-        save_m_str = xstrdup(mp->m_str);
-      }
+      save_alt_m_keys = mp->m_alt != NULL ? xstrdup(mp->m_alt->m_keys) : NULL;
       map_str = eval_map_expr(mp, NUL);
 
       if ((map_str == NULL || *map_str == NUL)) {
@@ -2409,11 +2406,18 @@ static int handle_mapping(int *keylenp, const bool *timedout, int *mapdepth)
 
       if (save_m_noremap != REMAP_YES) {
         noremap = save_m_noremap;
-      } else if (strncmp(map_str, save_m_keys != NULL ? save_m_keys : mp->m_keys,
-                         (size_t)keylen) != 0) {
-        noremap = REMAP_YES;
-      } else {
+      } else if (save_m_expr
+                 ? strncmp(map_str, save_m_keys, (size_t)keylen) == 0
+                 || (save_alt_m_keys != NULL
+                     && strncmp(map_str, save_alt_m_keys,
+                                strlen(save_alt_m_keys)) == 0)
+                 : strncmp(map_str, mp->m_keys, (size_t)keylen) == 0
+                 || (mp->m_alt != NULL
+                     && strncmp(map_str, mp->m_alt->m_keys,
+                                strlen(mp->m_alt->m_keys)) == 0)) {
         noremap = REMAP_SKIP;
+      } else {
+        noremap = REMAP_YES;
       }
       i = ins_typebuf(map_str, noremap, 0, true, cmd_silent || save_m_silent);
       if (save_m_expr) {
@@ -2421,7 +2425,7 @@ static int handle_mapping(int *keylenp, const bool *timedout, int *mapdepth)
       }
     }
     xfree(save_m_keys);
-    xfree(save_m_str);
+    xfree(save_alt_m_keys);
     *keylenp = keylen;
     if (i == FAIL) {
       return map_result_fail;
diff --git a/src/nvim/mapping.c b/src/nvim/mapping.c
index 167111f3ae..dfb540da84 100644
--- a/src/nvim/mapping.c
+++ b/src/nvim/mapping.c
@@ -151,7 +151,9 @@ static void mapblock_free(mapblock_T **mpp)
 {
   mapblock_T *mp = *mpp;
   xfree(mp->m_keys);
-  if (!mp->m_simplified) {
+  if (mp->m_alt != NULL) {
+    mp->m_alt->m_alt = NULL;
+  } else {
     NLUA_CLEAR_REF(mp->m_luaref);
     xfree(mp->m_str);
     xfree(mp->m_orig_str);
@@ -493,13 +495,13 @@ static int str_to_mapargs(const char *strargs, bool is_unmap, MapArguments *mapa
   return 0;
 }
 
-/// @param args  "rhs", "rhs_lua", "orig_rhs", "expr", "silent", "nowait", "replace_keycodes" and
-///              and "desc" fields are used.
-///              "rhs", "rhs_lua", "orig_rhs" fields are cleared if "simplified" is false.
+/// @param args  "rhs", "rhs_lua", "orig_rhs", "expr", "silent", "nowait",
+///              "replace_keycodes" and "desc" fields are used.
 /// @param sid  0 to use current_sctx
-static void map_add(buf_T *buf, mapblock_T **map_table, mapblock_T **abbr_table, const char *keys,
-                    MapArguments *args, int noremap, int mode, bool is_abbr, scid_T sid,
-                    linenr_T lnum, bool simplified)
+static mapblock_T *map_add(buf_T *buf, mapblock_T **map_table, mapblock_T **abbr_table,
+                           const char *keys, MapArguments *args, int noremap, int mode,
+                           bool is_abbr, scid_T sid, linenr_T lnum, bool simplified)
+  FUNC_ATTR_NONNULL_RET
 {
   mapblock_T *mp = xcalloc(1, sizeof(mapblock_T));
 
@@ -516,11 +518,6 @@ static void map_add(buf_T *buf, mapblock_T **map_table, mapblock_T **abbr_table,
   mp->m_str = args->rhs;
   mp->m_orig_str = args->orig_rhs;
   mp->m_luaref = args->rhs_lua;
-  if (!simplified) {
-    args->rhs = NULL;
-    args->orig_rhs = NULL;
-    args->rhs_lua = LUA_NOREF;
-  }
   mp->m_keylen = (int)strlen(mp->m_keys);
   mp->m_noremap = noremap;
   mp->m_nowait = args->nowait;
@@ -551,6 +548,7 @@ static void map_add(buf_T *buf, mapblock_T **map_table, mapblock_T **abbr_table,
     mp->m_next = map_table[n];
     map_table[n] = mp;
   }
+  return mp;
 }
 
 /// Sets or removes a mapping or abbreviation in buffer `buf`.
@@ -571,6 +569,7 @@ static int buf_do_map(int maptype, MapArguments *args, int mode, bool is_abbrev,
   // mappings/abbreviations, not the globals.
   mapblock_T **map_table = args->buffer ? buf->b_maphash : maphash;
   mapblock_T **abbr_table = args->buffer ? &buf->b_first_abbr : &first_abbr;
+  mapblock_T *mp_result[2] = { NULL, NULL };
 
   // For ":noremap" don't remap, otherwise do remap.
   int noremap = args->script ? REMAP_SCRIPT
@@ -805,19 +804,16 @@ static int buf_do_map(int maptype, MapArguments *args, int mode, bool is_abbrev,
                 mp->m_mode &= ~mode;  // remove mode bits
                 if (mp->m_mode == 0 && !did_it) {  // reuse entry
                   XFREE_CLEAR(mp->m_desc);
-                  if (!mp->m_simplified) {
+                  if (mp->m_alt != NULL) {
+                    mp->m_alt = mp->m_alt->m_alt = NULL;
+                  } else {
                     NLUA_CLEAR_REF(mp->m_luaref);
-                    XFREE_CLEAR(mp->m_str);
-                    XFREE_CLEAR(mp->m_orig_str);
+                    xfree(mp->m_str);
+                    xfree(mp->m_orig_str);
                   }
                   mp->m_str = args->rhs;
                   mp->m_orig_str = args->orig_rhs;
                   mp->m_luaref = args->rhs_lua;
-                  if (!keyround1_simplified) {
-                    args->rhs = NULL;
-                    args->orig_rhs = NULL;
-                    args->rhs_lua = LUA_NOREF;
-                  }
                   mp->m_noremap = noremap;
                   mp->m_nowait = args->nowait;
                   mp->m_silent = args->silent;
@@ -831,6 +827,7 @@ static int buf_do_map(int maptype, MapArguments *args, int mode, bool is_abbrev,
                   if (args->desc != NULL) {
                     mp->m_desc = xstrdup(args->desc);
                   }
+                  mp_result[keyround - 1] = mp;
                   did_it = true;
                 }
               }
@@ -889,13 +886,24 @@ static int buf_do_map(int maptype, MapArguments *args, int mode, bool is_abbrev,
     }
 
     // Get here when adding a new entry to the maphash[] list or abbrlist.
-    map_add(buf, map_table, abbr_table, lhs, args, noremap, mode, is_abbrev,
-            0,  // sid
-            0,  // lnum
-            keyround1_simplified);
+    mp_result[keyround - 1] = map_add(buf, map_table, abbr_table, lhs,
+                                      args, noremap, mode, is_abbrev,
+                                      0,  // sid
+                                      0,  // lnum
+                                      keyround1_simplified);
+  }
+
+  if (mp_result[0] != NULL && mp_result[1] != NULL) {
+    mp_result[0]->m_alt = mp_result[1];
+    mp_result[1]->m_alt = mp_result[0];
   }
 
 theend:
+  if (mp_result[0] != NULL || mp_result[1] != NULL) {
+    args->rhs = NULL;
+    args->orig_rhs = NULL;
+    args->rhs_lua = LUA_NOREF;
+  }
   return retval;
 }
 
@@ -2348,12 +2356,19 @@ void f_mapset(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   xfree(unmap_args.rhs);
   xfree(unmap_args.orig_rhs);
 
+  mapblock_T *mp_result[2] = { NULL, NULL };
+
+  mp_result[0] = map_add(curbuf, map_table, abbr_table, lhsraw, &args,
+                         noremap, mode, is_abbr, sid, lnum, false);
   if (lhsrawalt != NULL) {
-    map_add(curbuf, map_table, abbr_table, lhsrawalt, &args, noremap, mode, is_abbr,
-            sid, lnum, true);
+    mp_result[1] = map_add(curbuf, map_table, abbr_table, lhsrawalt, &args,
+                           noremap, mode, is_abbr, sid, lnum, true);
+  }
+
+  if (mp_result[0] != NULL && mp_result[1] != NULL) {
+    mp_result[0]->m_alt = mp_result[1];
+    mp_result[1]->m_alt = mp_result[0];
   }
-  map_add(curbuf, map_table, abbr_table, lhsraw, &args, noremap, mode, is_abbr,
-          sid, lnum, false);
 }
 
 /// "maplist()" function
diff --git a/src/nvim/mapping_defs.h b/src/nvim/mapping_defs.h
index 05b8aef23a..4a04b1ebfb 100644
--- a/src/nvim/mapping_defs.h
+++ b/src/nvim/mapping_defs.h
@@ -10,6 +10,9 @@ enum { MAXMAPLEN = 50, };  ///< Maximum length of key sequence to be mapped.
 typedef struct mapblock mapblock_T;
 struct mapblock {
   mapblock_T *m_next;       ///< next mapblock in list
+  mapblock_T *m_alt;        ///< pointer to mapblock of the same mapping
+                            ///< with an alternative form of m_keys, or NULL
+                            ///< if there is no such mapblock
   char *m_keys;             ///< mapped from, lhs
   char *m_str;              ///< mapped to, rhs
   char *m_orig_str;         ///< rhs as entered by the user