gears.debug: Import

So far this only contains an "assert()" function, but I guess this could be
enhance. For example, a function which pretty-prints a table's contents might be
useful to have.

Signed-off-by: Uli Schlachter <psychon@znc.in>

lib/gears/debug.lua.in

@@ -0,0 +1,23 @@
+---------------------------------------------------------------------------
+-- @author Uli Schlachter
+-- @copyright 2010 Uli Schlachter
+-- @release @AWESOME_VERSION@
+---------------------------------------------------------------------------
+
+local error = error
+local tostring = tostring
+local traceback = debug.traceback
+
+module("gears.debug")
+
+--- Check that the given condition holds true, else throw an error
+-- @param cond If this is false, throw a lua error with a backtrace.
+-- @param message Message to print in the error (optional).
+function assert(cond, message)
+    local message = message or cond
+    if not cond then
+        error(traceback("Assertion failed: '" .. tostring(message) .. "'"))
+    end
+end
+
+-- vim: filetype=lua:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=80

lib/gears/init.lua.in

@@ -5,6 +5,7 @@
 ---------------------------------------------------------------------------
 
 require("gears.color")
+require("gears.debug")
 require("gears.object")
 require("gears.sort")