Backwards compat code.

init.lua

@@ -1,8 +1,42 @@
 
 digilines = {}
 
--- Backwards compat.
-rawset(_G, "digiline", digilines)
+-- Backwards compatibility code.
+-- We define a proxy table whose methods can be called with the
+-- `foo:bar` notation, and it will redirect the call to the
+-- real function, dropping the first implicit argument.
+local digiline; digiline = setmetatable({}, {
+	__index = function(_, k)
+		-- Get method from real table.
+		local v = digilines[k]
+		if type(v) == "function" then
+			-- We need to wrap functions in order to ignore
+			-- the implicit `self` argument.
+			local f = v
+			return function(self, ...)
+				-- Trap invalid calls of the form `digiline.foo(...)`.
+				assert(self == digiline)
+				return f(...)
+			end
+		end
+		return v
+	end,
+})
+rawset(_G, "digiline", digiline)
+
+-- Let's test our proxy table.
+function digilines._testproxy(x)
+	return x
+end
+
+-- Test using old `digiline:foobar` form.
+assert(digiline:_testproxy("foobar") == "foobar")
+
+-- Test using new `digilines.foobar` form.
+assert(digilines._testproxy("foobar") == "foobar")
+
+-- Test calling incorrect form raises an error.
+assert(not pcall(function() digiline._testproxy("foobar") end))
 
 local modpath = minetest.get_modpath("digilines")
 dofile(modpath .. "/presetrules.lua")