fix(exrc): exrc knows its own location (#34638)

fix(exrc): lua exrc files know their location

Problem:
'exrc' files are inherently bound to their location / workspace and
therefore require to "know" their location on the filesystem. However,
currently using `debug.getinfo(1, 'S')` returns `"<nvim>"`.

Solution:
Include the filepath as chunkname in `loadstring()` and `nlua_exec()`.

src/nvim/api/deprecated.c

@@ -62,7 +62,7 @@ Object nvim_execute_lua(String code, Array args, Arena *arena, Error *err)
   FUNC_API_DEPRECATED_SINCE(7)
   FUNC_API_REMOTE_ONLY
 {
-  return nlua_exec(code, args, kRetObject, arena, err);
+  return nlua_exec(code, NULL, args, kRetObject, arena, err);
 }
 
 /// Gets the buffer number

src/nvim/api/vim.c

@@ -513,7 +513,7 @@ Object nvim_exec_lua(String code, Array args, Arena *arena, Error *err)
   FUNC_API_REMOTE_ONLY
 {
   // TODO(bfredl): convert directly from msgpack to lua and then back again
-  return nlua_exec(code, args, kRetObject, arena, err);
+  return nlua_exec(code, NULL, args, kRetObject, arena, err);
 }
 
 /// Calculates the number of display cells occupied by `text`.

src/nvim/eval.lua

@@ -2421,7 +2421,8 @@ M.funcs = {
       	<SID>		"<SNR>123_"  where "123" is the
       			current script ID  |<SID>|
       	<script>	sourced script file, or script file
-      			where the current function was defined
+      			where the current function was defined.
+      			Use |debug.getinfo()| in Lua scripts.
       	<stack>		call stack
       	<cword>		word under the cursor
       	<cWORD>		WORD under the cursor

src/nvim/lua/executor.c

@@ -1512,17 +1512,20 @@ int typval_exec_lua_callable(LuaRef lua_cb, int argcount, typval_T *argvars, typ
 /// Used for nvim_exec_lua() and internally to execute a lua string.
 ///
 /// @param[in]  str  String to execute.
+/// @param[in]  chunkname Chunkname, defaults to "<nvim>".
 /// @param[in]  args array of ... args
 /// @param[in]  mode Whether and how the the return value should be converted to Object
 /// @param[in] arena  can be NULL, then nested allocations are used
 /// @param[out]  err  Location where error will be saved.
 ///
 /// @return Return value of the execution.
-Object nlua_exec(const String str, const Array args, LuaRetMode mode, Arena *arena, Error *err)
+Object nlua_exec(const String str, const char *chunkname, const Array args, LuaRetMode mode,
+                 Arena *arena, Error *err)
 {
   lua_State *const lstate = global_lstate;
 
-  if (luaL_loadbuffer(lstate, str.data, str.size, "<nvim>")) {
+  const char *name = (chunkname && chunkname[0]) ? chunkname : "<nvim>";
+  if (luaL_loadbuffer(lstate, str.data, str.size, name)) {
     size_t len;
     const char *errstr = lua_tolstring(lstate, -1, &len);
     api_set_error(err, kErrorTypeValidation, "Lua: %.*s", (int)len, errstr);

src/nvim/lua/executor.h

@@ -26,7 +26,7 @@ typedef struct {
 } nlua_ref_state_t;
 
 #define NLUA_EXEC_STATIC(cstr, arg, mode, arena, err) \
-  nlua_exec(STATIC_CSTR_AS_STRING(cstr), arg, mode, arena, err)
+  nlua_exec(STATIC_CSTR_AS_STRING(cstr), NULL, arg, mode, arena, err)
 
 #define NLUA_CLEAR_REF(x) \
   do { \

src/nvim/main.c

@@ -961,7 +961,7 @@ static void remote_request(mparm_T *params, int remote_args, char *server_addr,
   ADD_C(a, CSTR_AS_OBJ(connect_error));
   ADD_C(a, ARRAY_OBJ(args));
   String s = STATIC_CSTR_AS_STRING("return vim._cs_remote(...)");
-  Object o = nlua_exec(s, a, kRetObject, NULL, &err);
+  Object o = nlua_exec(s, NULL, a, kRetObject, NULL, &err);
   kv_destroy(args);
   if (ERROR_SET(&err)) {
     fprintf(stderr, "%s\n", err.msg);
@@ -2062,7 +2062,8 @@ static void do_exrc_initialization(void)
     str = nlua_read_secure(VIMRC_LUA_FILE);
     if (str != NULL) {
       Error err = ERROR_INIT;
-      nlua_exec(cstr_as_string(str), (Array)ARRAY_DICT_INIT, kRetNilBool, NULL, &err);
+      nlua_exec(cstr_as_string(str), "@"VIMRC_LUA_FILE, (Array)ARRAY_DICT_INIT, kRetNilBool, NULL,
+                &err);
       xfree(str);
       if (ERROR_SET(&err)) {
         semsg("Error in %s:", VIMRC_LUA_FILE);

src/nvim/options.lua

@@ -2792,6 +2792,8 @@ local options = {
         Unset 'exrc' to stop further searching of 'exrc' files in parent
         directories, similar to |editorconfig.root|.
 
+        To get its own location, Lua exrc files can use |debug.getinfo()|.
+
         Compare 'exrc' to |editorconfig|:
         - 'exrc' can execute any code; editorconfig only specifies settings.
         - 'exrc' is Nvim-specific; editorconfig works in other editors.