Re: is there a way to rethrow errors so that their stack trace is preserved?

[Tomas Guisasola Gorham <tomas@...>]

	Hi Sam

	Maybe this works for you (I've skipped part of your original code,
but it stays the same; note the modification in opts table!):

> We want to handle some errors, but for syntax and type errors we would
> like to be able to "pass them" up to the lua
> standalone, preserving the backtrace, which often shows exactly what happened.
skip...
> -- shows how bug locations are masked by during error catch and rethrow
>
> opts = {raw=1, pcall=2, xpcall=3} -- I've changed this line
>
> kind = assert(opts[arg[1]], "arg1 is missing")
>
> -- example utility function, this might be called by many locations in the code,
> -- when it dies, but bug is in how it is called, not here
> function double(_)
>    return 2 * _
> end
>
> -- this function has a bug, it is attempting to double a table
> function some_function()
>    local _ = double{}
>    return _
> end
skip...

--[[
Using xpcall, notice that the error message is a bit different of the
"raw" call, but contains the same information:

traceable.lua:10: attempt to perform arithmetic on local '_' (a table value)
stack traceback:
        traceable.lua:10: in function 'double'
        traceable.lua:15: in function <traceable.lua:14>
        [C]: in function 'xpcall'
        traceable.lua:71: in main chunk
        [C]: ?

--]]

if kind == opts.xpcall then
    local ok, err_or_result = xpcall(some_function, debug.traceback)
    if not ok then
        print (err_or_result)
    end
end

	Regards,
		Tomás