[Tarantool-patches] [PATCH v20 6/7] box: implement box.lib module

[Cyrill Gorcunov]

On Wed, Apr 07, 2021 at 10:28:09PM +0200, Vladislav Shpilevoy wrote:
> >>
> >> Actually this snippet comes from popen code where
> >> we have wrappers on lua level and test for metamethods.
> >> While it doesn't hurt it makes no much sense in current
> >> code, thanks! Will drop.
> > 
> > Heh, in real we need these to handle metamethods such as
> > "module:load". I added a comment into the code.
> 
> For methods you need to use the metatype. It is defined as
> luaL_register_type(), where you can add methods, not just
> __index. The latter is more for, well, indexing. Getting an
> attribute, for example. See an example in lua/popen.c.
> 
> Methods should not end up in __index.

Wait. Here is what I have now

void
box_lua_lib_init(struct lua_State *L)
{
	func_hash = mh_strnptr_new();
	if (func_hash == NULL)
		panic("box.lib: Can't allocate func hash table");

	static const struct luaL_Reg top_methods[] = {
		{ "load",		lbox_module_load	},
		{ NULL, NULL },
	};
	luaL_register(L, "box.lib", top_methods);
	lua_pop(L, 1);

	static const struct luaL_Reg lbox_module_methods[] = {
		{ "unload",		lbox_module_unload	},
		{ "load",		lbox_module_load_func	},
		{ "__index",		lbox_module_index	},
		{ "__serialize",	lbox_module_serialize	},
		{ "__gc",		lbox_module_gc		},
		{ NULL, NULL },
	};
	luaL_register_type(L, uname_lib, lbox_module_methods);
	...
}

If I don't lookup for key being some nonnil value in __index
(ie those 5 lines) then module:load simply stop working. As
far as I understand the __index is called when Lua looks up
for a key in table. It sends "load" there and since it is
in metatable it executes lbox_module_load_func as it should.
What I'm missing?