registerFns doesn't build when lang=lua54

[nurpax]

Looks like there's no luaL_findtable in Lua 5.4 so the registerFns function fails to build.

ziglua/src/lib.zig

Line 2813 in beb0b78

_ = c.luaL_findtable(@ptrCast(lua), registry_index, "_LOADED", 1);

[nurpax]

Actually this was already failing to build when I chose lang=lua53 but I thought luaL_findtable was indeed removed in 5.4 and I was suspecting I saw some kind of an incremental build bug with Zig.

[nurpax]

Yeah, I think it was still there in 5.3 but only when built for compat:

C:\Users\janne\dev\zig-ast\t>rg findtable
lua-5.3.6\src\lauxlib.c
855:static const char *luaL_findtable (lua_State *L, int idx,
899:  luaL_findtable(L, LUA_REGISTRYINDEX, LUA_LOADED_TABLE, 1);
904:    if (luaL_findtable(L, 0, modname, sizehint) != NULL)

/*
** {======================================================
** Compatibility with 5.1 module functions
** =======================================================
*/
#if defined(LUA_COMPAT_MODULE)

static const char *luaL_findtable (lua_State *L, int idx,
                                   const char *fname, int szhint) {

[natecraddock]

This seems closely related to #42

I think the issue here is that older versions of Lua use luaL_register while newer ones use luaL_newlib. Maybe what ziglua needs is a higher-level function that works the same for all versions of Lua?

Also makes me wonder how we should handle LUA_COMPAT_MODULE (if at all)

[nurpax]

I'm not sure what to do about LUA_COMPAT_MODULE. I did notice though that the luaL_findtable is not present anymore even under LUA_COMPAT_MODULE in Lua 5.4.

In my code it was easy to work around that the function didn't compile, I just copied it into my own project:

fn registerFns2(lua: *Lua, funcs: []const ziglua.FnReg) void {
    for (funcs) |f| {
        lua.pushFunction(f.func.?);
        lua.setField(-2, f.name);
    }
}
...
fn register_L_Player(lua: *Lua) !void {
    try lua.newMetatable("L_Player");
    lua.pushValue(-1);
    lua.setField(-2, "__index");
    const methods = [_]ziglua.FnReg{
        .{ .name = "incScore", .func = ziglua.wrap(L_Player_incScore) },
        .{ .name = "setScore", .func = ziglua.wrap(L_Player_setScore) },
        .{ .name = "getScore", .func = ziglua.wrap(L_Player_getScore) },
    };
    registerFns2(lua, &methods);
    lua.register("Player", ziglua.wrap(L_Player_create));
}