Re: Error handling

[Romulo Bahiense <romulo@...>]

> function raise(errtable)
>     error(setmetatable(errtable, errtablemt))
> end

When I arrived home last night, I realized this will not work as 
expected, because __tostring metamethod would be called only when the 
message is displayed.

The first potential fix is to calling tostring before ivoking 'error()', 
but it will break the meaning of having a table anyway.

function raise(errtable)
    error(tostring(setmetatable(errtable, errtablemt)))
end

-- Which could be converted to:
function raise(errtable)
    error(
        string.format(
            'An error ocurred with error code %d: %s.\n%s',
            errtable.code,
            errtable.msg,
            debug.traceback()
        )
    )
end


The second method, probably the best:

errtablemt = {
    __tostring = function(t)
        return string.format(
            'An error ocurred with error code %d: %s.\n%s',
            t.code,
            t.msg,
            t.stack -- Note that I don't call debug.traceback() anymore
        )
    end
}

function raise(errtable)
    errtable.stack = debug.traceback()
    error(setmetatable(errtable, errtablemt))
end


With this version you will have the correct stack trace as long as you want.

--rb