fix(api): nvim_set_keymap() throws error even in pcall() #33228

Problem: When `nvim_set_keymap` tries to overwrite a `<unique>` mapping,
it throws an error even when called in `pcall`.

Solution: src/nvim/mapping.c:buf_do_map no longer calls `semsg`. Its
callers now decide whether to ignore the error, or use
`semsg` (not caught)/`api_set_error` (caught by `pcall`).

(cherry picked from commit ec18ebcb41)

src/nvim/mapping.c

@@ -681,12 +681,7 @@ static int buf_do_map(int maptype, MapArguments *args, int mode, bool is_abbrev,
           if ((mp->m_mode & mode) != 0
               && mp->m_keylen == len
               && strncmp(mp->m_keys, lhs, (size_t)len) == 0) {
-            if (is_abbrev) {
+            retval = 6;
-              semsg(_(e_global_abbreviation_already_exists_for_str), mp->m_keys);
-            } else {
-              semsg(_(e_global_mapping_already_exists_for_str), mp->m_keys);
-            }
-            retval = 5;
             goto theend;
           }
         }
@@ -799,11 +794,6 @@ static int buf_do_map(int maptype, MapArguments *args, int mode, bool is_abbrev,
                 did_it = true;
                 break;
               } else if (args->unique) {
-                if (is_abbrev) {
-                  semsg(_(e_abbreviation_already_exists_for_str), p);
-                } else {
-                  semsg(_(e_mapping_already_exists_for_str), p);
-                }
                 retval = 5;
                 goto theend;
               } else {
@@ -962,6 +952,7 @@ theend:
 ///         - 2 for no match
 ///         - 4 for out of mem (deprecated, WON'T HAPPEN)
 ///         - 5 for entry not unique
+///         - 6 for buflocal unique entry conflicts with global entry
 ///
 int do_map(int maptype, char *arg, int mode, bool is_abbrev)
 {
@@ -2637,16 +2628,47 @@ static void do_exmap(exarg_T *eap, int isabbrev)
   char *cmdp = eap->cmd;
   int mode = get_map_mode(&cmdp, eap->forceit || isabbrev);
 
-  switch (do_map((*cmdp == 'n') ? MAPTYPE_NOREMAP
+  int maptype;
-                                : (*cmdp == 'u') ? MAPTYPE_UNMAP : MAPTYPE_MAP,
+  if (*cmdp == 'n') {
-                 eap->arg, mode, isabbrev)) {
+    maptype = MAPTYPE_NOREMAP;
+  } else if (*cmdp == 'u') {
+    maptype = MAPTYPE_UNMAP;
+  } else {
+    maptype = MAPTYPE_MAP;
+  }
+  MapArguments parsed_args;
+  int result = str_to_mapargs(eap->arg, maptype == MAPTYPE_UNMAP, &parsed_args);
+  switch (result) {
+  case 0:
+    break;
+  case 1:
+    emsg(_(e_invarg));
+    goto free_rhs;
+    break;
+  default:
+    assert(false && "Unknown return code from str_to_mapargs!");
+    goto free_rhs;
+  }
+  switch (buf_do_map(maptype, &parsed_args, mode, isabbrev, curbuf)) {
   case 1:
     emsg(_(e_invarg));
     break;
   case 2:
     emsg(isabbrev ? _(e_noabbr) : _(e_nomap));
     break;
+  case 5:
+    semsg(isabbrev ? _(e_abbreviation_already_exists_for_str)
+                   : _(e_mapping_already_exists_for_str),
+          parsed_args.lhs);
+    break;
+  case 6:
+    semsg(isabbrev ? _(e_global_abbreviation_already_exists_for_str)
+                   : _(e_global_mapping_already_exists_for_str),
+          parsed_args.lhs);
   }
+free_rhs:
+  xfree(parsed_args.rhs);
+  xfree(parsed_args.orig_rhs);
 }
 
 /// ":abbreviate" and friends.
@@ -2808,6 +2830,12 @@ void modify_keymap(uint64_t channel_id, Buffer buffer, bool is_unmap, String mod
                   is_abbrev ? e_abbreviation_already_exists_for_str
                             : e_mapping_already_exists_for_str, lhs.data);
     goto fail_and_free;
+    break;
+  case 6:
+    api_set_error(err, kErrorTypeException,
+                  is_abbrev ? e_global_abbreviation_already_exists_for_str
+                            : e_global_mapping_already_exists_for_str, lhs.data);
+    goto fail_and_free;
   default:
     assert(false && "Unrecognized return code!");
     goto fail_and_free;

test/functional/api/keymap_spec.lua

@@ -1465,4 +1465,24 @@ describe('nvim_buf_set_keymap, nvim_buf_del_keymap', function()
     eq(1, exec_lua [[return GlobalCount]])
     eq('\nNo mapping found', n.exec_capture('nmap <C-I>'))
   end)
+
+  it('does not overwrite in <unique> mappings', function()
+    api.nvim_buf_set_keymap(0, 'i', 'lhs', 'rhs', {})
+    eq(
+      'E227: Mapping already exists for lhs',
+      pcall_err(api.nvim_buf_set_keymap, 0, 'i', 'lhs', 'rhs', { unique = true })
+    )
+
+    api.nvim_buf_set_keymap(0, 'ia', 'lhs2', 'rhs2', {})
+    eq(
+      'E226: Abbreviation already exists for lhs2',
+      pcall_err(api.nvim_buf_set_keymap, 0, 'ia', 'lhs2', 'rhs2', { unique = true })
+    )
+
+    api.nvim_set_keymap('n', 'lhs', 'rhs', {})
+    eq(
+      'E225: Global mapping already exists for lhs',
+      pcall_err(api.nvim_buf_set_keymap, 0, 'n', 'lhs', 'rhs', { unique = true })
+    )
+  end)
 end)