Add better error handling for debugger

debugger.lua

@@ -28,14 +28,19 @@ end
 local function debugREPL(onResult, debugArgs)
   local globalEnv = copyObject(_ENV)
   globalEnv._debug = debugArgs
+  local shouldExit = false
+  globalEnv.exit = function()
+    shouldExit = true
+  end
   local result, retval
   repeat
     result, retval = execDebug(globalEnv)
     if result and type(onResult) == "function" then
       onResult(retval)
     end
-  until not result
-  return retval
+  until shouldExit or not result
+  local success = result and shouldExit
+  return success, (not success and retval) or nil
 end
 
 return { debugREPL = debugREPL, execDebug = execDebug }