simple function arguments type check function

validator.lua

local function type_check(...)
  local function type_name(t)
    assert(type(t) == 'string')

    if t == 't' or t == 'table' then return 'table'  end
    if t == 's' or t == 'string' then return 'string'  end
    if t == 'n' or t == 'number' then return 'number'  end
    if t == 'b' or t == 'boolean' then return 'boolean'  end
    if t == 'f' or t == 'function' then return 'f' end
    if t == 'nil' then return 'nil' end
    if t == 'th' or t == 'table' then return 'thread'  end
    if t == 'u' or t == 'userdata' then return 'userdata' end

    error(string.format("invalid type name '%s'", t))
  end

  local t = {...}

  for _, v in pairs(t) do
    assert(type(v) == 'table', 'Expected table, got %s', type(v))

    local arg_type = type(v[1])
    local _type, is_optional = v[2]:gsub('^!', '')

    if is_optional == 1 then
      is_optional = true
    else
      is_optional = false
    end

    local expected_type = type_name(_type)

    if is_optional then
      assert((arg_type == expected_type) or arg_type == 'nil', string.format("Expected %s or nil, got %s", expected_type, type(v[1])))
    else
      assert(arg_type == expected_type, string.format("Expected %s, got %s", expected_type, type(v[1])))
    end
  end
end


function test(a, b, c)
  type_check({a, 'n'}, {b, 's'}, {c, '!t'})
end

print('===case1===')
test(1, 'a', {1})
print('===case2===')
test(1, 'a', nil)
print('===case3===')
test(1, 2, 3)