Add debug module

Readme.md

@@ -222,6 +222,18 @@ This is best left explicit. First, you shouldn't be using numbered field keys if
 4. [`json`](https://json.org)
   * Not recommended
 
+## `debug`
+
+`modlib.debug` offers utilities dumping program state in tables.
+
+### `variables(stacklevel)`
+
+Dumps local variables, upvalues and the function environment of the function at the given stacklevel (default `1`).
+
+### `stack(stacklevel)`
+
+Dumps function info & variables for all functions in stack, starting with stacklevel (default `1`).
+
 ## Release Notes
 
 ### `rolling-68`

debug.lua

@@ -1,15 +1,16 @@
-local function gather_info()
+function variables(stacklevel)
+	stacklevel = (stacklevel or 1) + 1
 	local locals = {}
 	local index = 1
 	while true do
-        local name, value = debug.getlocal(2, index)
+		local name, value = debug.getlocal(stacklevel, index)
 		if not name then break end
 		table.insert(locals, {name, value})
 		index = index + 1
 	end
 	local upvalues = {}
-    local func = debug.getinfo(2).func
-    local envs = getfenv(func)
+	local func = debug.getinfo(stacklevel).func
+	local fenv = getfenv(func)
 	index = 1
 	while true do
 		local name, value = debug.getupvalue(func, index)
@@ -20,15 +21,23 @@ local function gather_info()
 	return {
 		locals = locals,
 		upvalues = upvalues,
-        [envs == _G and "globals" or "envs"] = envs
+		fenv = fenv,
+		fenv_global = fenv == _G
 	}
 end
 
-local c = 3
-function test()
-    local a = 1
-    b = 2
-    error(gather_info().upvalues[1][1])
+function stack(stacklevel)
+	stacklevel = (stacklevel or 1) + 1
+	local stack = {}
+	while true do
+		local info = debug.getinfo(stacklevel, "nfSlu")
+		if not info then
+			break
+		end
+		info.func = tostring(info.func)
+		info.variables = variables(level)
+		stack[stacklevel - 1] = info
+		stacklevel = stacklevel + 1
+	end
+	return stack
 end
-
-test()

init.lua

@@ -53,7 +53,8 @@ for _, file in pairs{
 	"binary",
 	"b3d",
 	"bluon",
-	"persistence"
+	"persistence",
+	"debug"
 } do
 	modules[file] = file
 end