Subject: Re: Cabal, Haskell Platform
From: Gershom B <[email-masked]>
To: Duncan Coutts <[email-masked]>
Cc: Simon Peyton Jones <[email-masked]>, "Edward Yang ([email-masked])" <[email-masked]>, Ben Gamari <[email-masked]>, Austin Seipp <[email-masked]>, Randy Polen <[email-masked]>
Date: Sat, 31 Oct 2015 23:12:27 +0000

CC: Randy Polen who has done work on the windows HP installer.

I also have a patch to cabal sitting around that I would really like
pulled. (Duncan, Ed, help me out here? :-))

https://na01.safelinks.protection.outlook.com/?url=https%3a%2f%2fgithub.com%2fhaskell%2fcabal%2fpull%2f2820&data=01%7c01%7csimonpj%40064d.mgd.microsoft.com%7cf2b99314331343b86e6c08d2e248ca44%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=0IiqCw3MXEkrXxECRViyk7BJlYb1YRRV2460%2bzXBCIc%3d

This "default global constraints" option would provide an appropriate
fallback if the *nix stuff is not considered ready for primetime,
allowing global pinning of platform packages even absent shipping the
binaries.

In fact, with a minimal platform we don't even need to enforce one or
the other choice (or just not having a choice and using sandboxes
everywhere).

So I would like this patch pulled.

There seems to be a controversy though with the "no-reinstall" cabal
-- Plan Ed and Plan Duncan seem to involve different patchsets towards
roughly the same end. I gather people think Duncan's set would be more
comprehensive, but consider it less done? Either way, it would be good
for Duncan to confirm the relationship of the two sets and if it is
indeed a binary option between the two (which I understand to be the
case?).

Finally, on the other element of new platform -- there is a patch
already pulled to Cabal that enables a nicer interaction with msys
(https://na01.safelinks.protection.outlook.com/?url=https%3a%2f%2fgithub.com%2fhaskell%2fcabal%2fpull%2f2840&data=01%7c01%7csimonpj%40064d.mgd.microsoft.com%7cf2b99314331343b86e6c08d2e248ca44%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=jVd97wv9RHtF7JhQN18XmpBoZDMoxWE1XQ%2b8IIopTU8%3d). I think we need to go
through the platform and try to use a version with this patch to
implement msys interaction, and also to teach it to install the now
requested "official" mys installs (e.g. pointed to here:
https://na01.safelinks.protection.outlook.com/?url=https%3a%2f%2fgithub.com%2ffpco%2fstackage-content%2fblob%2fmaster%2fstack%2fstack-setup-2.yaml%23L20&data=01%7c01%7csimonpj%40064d.mgd.microsoft.com%7cf2b99314331343b86e6c08d2e248ca44%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=C7Tqk%2fV3O7chgN2bd7Nbv8EDbRGBiQEC%2bg3JhSIwnLo%3d).

I've been meaning to both do some actual work modifying the platform
build process (just to build less packages -- so, hopefully, easy!)
and put out a note about this, but got rather slammed by work
immediately following Haskell Exchange, and have just started to come
up for air.

Cheers,
Gershom

On Sat, Oct 31, 2015 at 6:56 PM, Duncan Coutts <[email-masked]> wrote:
> On Sat, 2015-10-31 at 21:47 +0000, Simon Peyton Jones wrote:
>
>> ·         GHC has for some time had the hooks to install multiple
>> instances of the same library without conflict, but Cabal does not (or
>> did not).  I know Duncan was planning to do this.   Will the Cabal
>> that comes with HP 8.0 have this ability?
>
> On this specific point, I've been working on this a lot recently. We'll
> be merging the new stuff into the main cabal-install development branch
> relatively soon. However that's not the end of the story. At this point
> in time I cannot say for certain if this new stuff will be on by default
> in the cabal-install we release to go with ghc 8.0, though I'm confident
> it would at least be included as a non-default tech preview.
>
> So we should work out when our cut-off time is when we have to decide if
> we can use this new code or if we have to go with an interim solution.
> Gershom, Austin and Ben and I should chat about this to work out the
> timing.
>
> --
> Duncan Coutts, Haskell Consultant
> Well-Typed LLP, https://na01.safelinks.protection.outlook.com/?url=http%3a%2f%2fwww.well-typed.com%2f&data=01%7c01%7csimonpj%40064d.mgd.microsoft.com%7cf2b99314331343b86e6c08d2e248ca44%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=mMV%2f18KhtzDZApsmYbHBCCQWecLgMxiGYP%2fFqE3uPy0%3d
>