[Haskell-beginners] Stackage latest snapshot

[Michael Snoyman]

On Wed, Sep 3, 2014 at 10:52 AM, Peter <voldermort at hotmail.com> wrote:

> Michael Snoyman <michael <at> snoyman.com> writes:
>
> > The preparing your system for Stackage page[1] has those auto-updated
> links available (e.g., GHC 7.8 exclusive is [2]).
>
> Thank you. I read the page at least 3 times, but missed that because the
> links redirected to the latest snapshot, and the Stackage server only has
> static snapshot links. Perhaps it should be made clearer that these links
> will redirect to the current snapshot, and add them to
> http://www.stackage.org/snapshots as well?
>
>
That would be a good idea if I wanted people to directly use those URLs,
which I think is generally a bad idea. The lack of explicitness about the
presence of a redirect there is a feature, not a bug ;).


> > You already identified the downside with this: you may magically be
> upgraded to a new version of a package. If you really want to do this, you
> can, but my recommendation is to manually decide to upgrade your Stackage
> snapshot consciously instead of letter an arbitrary Jenkins build server
> make the decision for you.
>
> I'm using Stackage as a QA'd Hackage. It sounds like you see it more as a
> server-side cabal freeze.
>
>
I'm not sure what distinction you're going for in this. Imagine the
following sequence of events:

* You set up your system to use Stackage, with September 1's snapshot being
active at the time.
* You install foo-1.1, with bar-1.1 depending on it.
* A new Stackage snapshot comes out, providing foo-1.2.
* You now try to install something depending on foo, and depending on the
alignment of the stars, cabal will either download a new foo or use the
already installed one.

In other words, the usage you seem to be implying is highly
non-deterministic, which I'd be very careful about using.

Michael
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.haskell.org/pipermail/beginners/attachments/20140903/66866ace/attachment.html>