Discussion: Add safeWithFile function

[David Feuer]

I think a lot of people have raised a lot of important concerns. Henning's
point, I think, is particularly enlightening: "I would not like the name
safeWithFile, because withFile is already safe. It's hGetContents that is
unsafe." It also composes very poorly—using the contents of more than one
file to compute a result will lead to a double application of deepseq. I'm
not sure how to address those concerns. One possible path is to have a
safeHGetContents, along with RULES in Control.DeepSeq to attempt to erase
the double deepseq.
I would support adding this function under the name `withFile`, in a new
module exported by the deepseq package, as Henning seems to be suggesting.
I don't think it's particularly important, but this pattern arises often
enough that I think it's worthwhile.

John L.

On Mon, Oct 13, 2014 at 12:14 AM, Henning Thielemann <
lemming at henning-thielemann.de> wrote:

>
> On Sun, 12 Oct 2014, Oliver Charles wrote:
>
>  Where are you suggesting this library goes? Your `safeWithFile` needs
>> `NFData`, but that's in `deepseq` which
>> isn't a dependency of `base`.
>>
>
> It would certainly be located in 'deepseq' or a dependent library. Maybe
> Control.DeepSeq.IO.withFile would be good. Then it would be clear, that it
> is just a deepseq variant of withFile.
>
> I would not like the name safeWithFile, because withFile is already safe.
> It's hGetContents that is unsafe.
>
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