1 files changed, 34 insertions, 0 deletions
diff --git a/etc/strict.lua b/etc/strict.lua
new file mode 100644
index 00000000..7c9fa159
--- /dev/null
+++ b/etc/strict.lua
@@ -0,0 +1,34 @@
+--
+-- strict.lua
+-- checks uses of undeclared global variables
+-- All global variables must be 'declared' through a regular assignment
+-- (even assigning nil will do) in a main chunk before being used
+-- anywhere or assigned to inside a function.
+--
+
+local mt = getmetatable(_G)
+if mt == nil then
+  mt = {}
+  setmetatable(_G, mt)
+end
+
+mt.__declared = {}
+
+mt.__newindex = function (t, n, v)
+  if not mt.__declared[n] then
+    local w = debug.getinfo(2, "S").what
+    if w ~= "main" and w ~= "C" then
+      error("assign to undeclared variable '"..n.."'", 2)
+    end
+    mt.__declared[n] = true
+  end
+  rawset(t, n, v)
+end
+  
+mt.__index = function (t, n)
+  if not mt.__declared[n] and debug.getinfo(2, "S").what ~= "C" then
+    error("variable '"..n.."' is not declared", 2)
+  end
+  return rawget(t, n)
+end
+