errfmt.hlua

--------------------------------------------------------------------------
--            __                    _                                   --
--           / _|___ _ _ _ __  __ _| |_   ___ _ _ _ _ ___ _ _           --
--          |  _/ _ \ '_| '  \/ _` |  _| / -_) '_| '_/ _ \ '_|          --
--          |_| \___/_| |_|_|_\__,_|\__|_\___|_| |_| \___/_|            --
--                                    |___|                             --
--------------------------------------------------------------------------
-- Error message formatter compatible with lua 5.0.x and 5.1.x.
-- Ugly but simple and self-contained.
--
-- @author:  andrew_zhilin@yahoo.com
-- @version: 0.6 beta
-- Copyright (C) 2008, 2009 by zOOn

-- NOTE: Using deprecated feature (arg).
-- NOTE: Shoud be compiled by hluac with -lua50 option.
--------------------------------------------------------------------------

--------------------------------------------------------------------------
-- require'strict' -- DEBUG:
local getn = table.getn 
local format,gsub  = string.format,string.gsub

--------------------------------------------------------------------------
-- errfmt :: (num, bool, ...) -> str
local function errfmt(argn,varargs,...)
  local MAX_TAB = 5
  local args  = {...}
  local argslen = #args
  argslen = (argn and argn > argslen) and argn or argslen

  local fun get_type
    | o@(_:'tab'|_:'udata') ->
    local mt = getmetatable(o)
    if  mt and mt.type and type(mt.type)=='function' then
      return o:type()
    else
      return type(o)
    end
    | o -> type(o)
  end

  local function atom(x)
    if type(x) == 'string' then 
      return format('%q:%s',x,'string') 
    else 
      return format('%s:%s',tostring(x), get_type(x)) end
  end
  
  local function key(x)
    if type(x) == 'number' then return ""
    else return '['..atom(x)..']='
    end
  end

  local function one_arg(i,x)
    local what = 'arg#'..i..":\t"
    if type(x) == 'table' then 
      local n = 0
      what ..='{'
      for k,v in pairs(x) do 
        what..=(key(k)..atom(v)..',')
        n += 1 if n == MAX_TAB then what ..=" ..." break end
      end
      what..='}:'..get_type(x)
    else what ..= atom(x) end
    what..='\n'
    return what
  end
  local res='pattern-match error:\n'
  
  if varargs ~= false then
    res ..= 'varargs possible after arg#'..argn..'.\n' 
  end
  if argn ~= 0 then 
    res..= argn.. ' args were expected; in fact we got:\n'
  end
  for i=1,argslen do
    res..=one_arg(i,args[i])
  end
  if debug and type(debug) == 'table' then
    -- NOTE: we remove '\t' from traceback to make easier for emacs
    -- to jump to errors
    return res..(gsub(debug.traceback(""),'\t',''))..'\n'
  else return res
  end
end

-- module return
return errfmt