Table Freezing

Tables can now be frozen at their current state to forbid any future modification. This action is irreversible and permanent for the lifespan of the table.

pluto
-- Disallowing any edits to the global environment table.
table.freeze(_G)
_G.string = {}
-- file.pluto:4: attempt to modify frozen table.

pluto
-- Creating a constant local that's associated with a frozen table.
local Frozen <const> = table.freeze({ 1, 2, 3 })
Frozen = {}
-- file.pluto:4: attempt to reassign constant.
Frozen[1] = "new value"
-- file.pluto:7: attempt to modify frozen table.
rawset(Frozen, "key", "value")
-- file.pluto:10: attempt to modify frozen table.

pluto
--- Trying to swap the value with the debug library.
for i = 1, 249 do
  local name, value = debug.getlocal(1, i)
  if name == "Frozen" then
    debug.setlocal(1, i, { ["key"] = "hello world" })
    -- file.pluto:5: attempt to modify local variable with a frozen table.
  end
end

What will this prevent?

All modifications to the table from within the Lua environment will be prevented, including those from the debug library.

caution

If you're going to use this for a sandbox, ensure you call table.freeze before any users can access the Lua environment, otherwise they can replace that function.