Re: Lua 5.4.0-alpha-rc1 behavior with closing methods errors
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- Subject: Re: Lua 5.4.0-alpha-rc1 behavior with closing methods errors
- From: David Heiko Kolf <david@...>
- Date: 2019年6月20日 13:19:11 +0200
phlnc8 wrote:
> with test2(), the _last_ closing error is reported (i.e. closing 'x').
> There is no traceback. The first encoutered errors (the failed assert
> withing the function body, and the error closing 'z') are raised, but
> then not reported..
>
> With this behavior, it looks like an error within the body of a block
> is "masked" by any error in a closing method.
>
> I think the expected behavior would be:
>
> 1. attempt to execute all the closing methods (as Lua-5.4.0 does now),
> but report _the first encountered error_, instead of the last (in this
> example, reporting the assert failure)
In C# the last error is reported and I actually think that is the right
decision.
<https://stackoverflow.com/questions/2911215/what-happens-if-a-finally-block-throws-an-exception>
Consider this program with two errors, where at least one is a
programming mistake:
do
local z
local <toclose> resource = setmetatable({}, {
__close = function ()
z.closed = true -- error 2, z might be nil
end
})
error "something went wrong" -- error 1
z = {}
end
If the first error is reported I will never even know that there was a
second error. And once I fixed the first error, I probably won't see
that there is problem with my __close function.
However, if the last error is reported, I can fix that and after fixing
it I will still see the first error.
Best regards,
David