Lua - automatic logging idea

log-minimal-demo.lua

-- load the log module
local log = require("log")

-- some function for demo
function add(a, b)
   return a+b
end

-- wrap the main script in a main function
function main()
   add(128, 293    )
   add(227, "43.23") -- internal conversion works
   add(227, "43,23") -- internal conversion fails -> program crashes
   add(983, 123    ) -- never reached
end

-- register functions for logging
log.Functions =
{
   ["add"] = true,
}

-- initialize the logging
log.initLog()

 -- call main func and writeLog in case of failure
xpcall(main, log.writeLog)

log.lua

log = {}

function convertTableToString_s(t) -- <<<
   local ret_t = {}

   local function convertTableToStringHelper(obj, cnt)

      local cnt=cnt or 0

      if type(obj) == "table" then
         table.insert(ret_t, "\n" .. string.rep("\t",cnt) .. "{\n")
         cnt = cnt+1
         for k,v in pairs(obj) do
            if type(k) == "string" then
               table.insert(ret_t, string.rep("\t",cnt) .. '["' .. k .. '"] = ')
            end
            if type(k) == "number" then
               table.insert(ret_t, string.rep("\t",cnt) .. "[" .. k.. "] = ")
            end
            convertTableToStringHelper(v, cnt)
            table.insert(ret_t, ",\n")
         end
         cnt = cnt-1
         table.insert(ret_t, string.rep("\t",cnt) .. "}")
      elseif type(obj) == "string" then
         table.insert(ret_t, string.format("%q",obj))
      else
         table.insert(ret_t, tostring(obj))
      end 
   end

   convertTableToStringHelper(t)
   return table.concat(ret_t)
end -- >>>

-- TODO check how to handle functions as parameter ?
-- TODO check how to handle elipse ... (nameless parameters) ?
function log.log(Event_s) -- <<<

   Info_t     = debug.getinfo(2, "n")
   Function_s = Info_t.name

   if log.Functions[Function_s] then

      local Data = {Function=Function_s, Event=Event_s}
      local UpValueCnt_n = 1
      local UpValues_t = {}
      
      while true do

         Name, Value = debug.getlocal(2, UpValueCnt_n)

         if (Event_s == "call") and (Name == '(*temporary)') then
            break
         end

         if (Name == nil) then
            break
         end

         if type(Value) == "string" then
            table.insert(UpValues_t, {["Name"]=Name, ["Type"]="string", ["Value"]=string.format("%q", Value)})
         end

         if type(Value) == "number" then
            table.insert(UpValues_t, {["Name"]=Name, ["Type"]="number", ["Value"]=tostring(Value)})
         end

         if type(Value) == "nil" then
            table.insert(UpValues_t, {["Name"]=Name, ["Type"]="nil"   , ["Value"]=tostring(Value)})
         end

         if type(Value) == "table" then
            table.insert(UpValues_t, {["Name"]=Name, ["Type"]="table" , ["Value"]=convertTableToString_s(Value)})
         end

         UpValueCnt_n = UpValueCnt_n + 1
      end

      if (Event_s == "return") then
         table.remove(UpValues_t) -- remove last entry, it's a Lua internal
      end
      Data.UpValues = UpValues_t

      table.insert(log.Data, Data)

      if (table.maxn(log.Data) > (log.Max or 20)) and (log.Max ~= 0) then
         table.remove(log.Data, 1)
      end
   end
end -- >>>

function log.writeLog() -- <<<
   if log.IsOn ~= true then
      return
   end

   local LogFile_h = io.open(log.File, "w+")
   if LogFile_h then
      for i,v in ipairs(log.Data or {}) do

         LogFile_h:write(v.Event .. " " .. v.Function,"\n")

         for _,p in ipairs(v.UpValues) do
            LogFile_h:write("   "..p.Name.." "..p.Type.." "..p.Value.."\n")
         end

         LogFile_h:write("────────────────────────────────────────────────\n")
      end

      LogFile_h:write(string.format("Time Stamp: %s\n" , os.date()))
      LogFile_h:write(string.format("Lua Version: %s\n", _VERSION ))
      --LogFile_h:write(string.format("Operating System: %s\n", (os.getenv("OSTYPE") or "windows") )) -- does not work. OSTYPE is available on my system but somehow I get nil here
      LogFile:close()
   else
      io.stderr:write("\nlog error: could not open '"..log.File.."' for writing\n")
   end
end -- >>>

function log.initLog() -- <<<
   if log.IsOn == true then
      debug.sethook(log.log, "cr") -- c and/or r
      log.Data = {}
   end
end -- >>>

-- default values for log <<<
log.IsOn  = true            -- logging on/off
log.File  = "./logfile.log" -- name of the log file
log.Max   = 20              -- maximum number of log entries, set to 0 to log everything, default is 20
-- >>>

return log

-- vim: fmr=<<<,>>> fdm=marker

logfile.log

call add
   a number 128
   b number 293
────────────────────────────────────────────────
return add
   a number 128
   b number 293
   (*temporary) number 421
────────────────────────────────────────────────
call add
   a number 227
   b string "43.23"
────────────────────────────────────────────────
return add
   a number 227
   b string "43.23"
   (*temporary) number 270.23
────────────────────────────────────────────────
call add
   a number 227
   b string "43,23"
────────────────────────────────────────────────
Time Stamp: Wed Jul  8 10:17:04 2015
Lua Version: Lua 5.2