We’re ramping up for the Stack 2 release, which contains a
number of changes. (If you want more information, check out
the changelog.) I’m not going to be covering all of those
changes in this blog post. Instead, today, I want to talk about
what the release process will look like, both for Stack itself and
Stack release process
I’ve created a new Stack
2 milestone on Github to track issues we want resolved before
release. I’m also now announcing a 2 week deadline for a feature
freeze. If you have a feature you believe belongs in Stack 2,
or a bug fix you’d like to see addressed in this release, now’s the
time to raise it. As usual, pull requests will be more likely to
result in changes happening, and the Stack team is always happy to
help people new to the codebase.
As of 2 weeks from today (May 8), we’ll enter a code
freeze period. We’ll cut a release branch and begin releasing
release candidates. New features will not be added to the release
candidate branch, and we will need to weigh carefully which bug
fixes are added to this branch to avoid destabilizing things too
I strongly encourage Stack users to begin experimenting with the
Stack master branch earlier rather than later. You can upgrade to
the latest master by running `stack upgrade --git`.
We will plan for at least a 3 week code freeze period, which may
be extended based on feedback from users. That would make the
earliest release of Stack 2 May 29.
Changes to Stackage
Last year, I wrote a few blog posts
about Pantry. I never really finished that series, and I think some
people were left wondering how this would affect Stack and Stackage
going forward. Let me give a bit more information, now that we know
how Pantry is going to work out. Big thanks to Kirill Zaborsky and
Sibi Prabakaran for all of their work on the Pantry changes.
Pantry is a library for representing Haskell source files in a
fully deterministic way. Each package ends up with a pantry tree
key, which is a hash of its contents, and some description of how
to get the source code. Examples would be from Hackage with a
specific revision, from a Git repository at a certain commit, or
from a tarball.
With Stack 2, we are overhauling the Stackage snapshot file
format to directly use Pantry. This fixes a long-standing
annoyance: we had different snapshot formats for Stackage itself
and for “custom snapshots” in Stack. Those are now unified. It also
addresses a long-standing concern in Stackage: the inability to
patch packages if necessary. By allowing package sources from
outside of Hackage, the Stackage Curator team will now have the
ability to patch packages as necessary.
We’ve already been generating new-style Stackage snapshot files,
which can be viewed at the commercialhaskell/stackage-snapshots
repo. Currently, we’re using the original Stackage build process,
generating the original LTS Haskell and Stackage Nightly snapshot
formats, and converting to the new format. In the next week or two,
we’ll be reversing that: using a new Stackage Curator build tool to
produce snapshot files and perform builds, and then for
compatibility generating the old file formats.
We don’t have a guarantee of how long we will continue to
support the original file format. There are no plans at all to ever
remove the existing files, but at some point in the future we will
stop generating compatibility files. We recommend tooling authors
using the snapshot files directly get in touch to discuss upgrade
paths. (I discussed this offline with some of the Nix contributor
team, but that work was never completed.)
Future: Pantry server
Pantry works via content-addressable storage: each tree and file
can be accessed via its hash. One plan we have for the future is to
write a Pantry server, which will allow Stack (and other tools) to
download package contents via the Pantry key instead of, for
example, needing to clone a Git repository. For compatibility with
tooling already familiar with HTTP(S) and Tarballs, we’ll likely
provide such an interface to this store as well.
That said: we are not including this feature in Stack 2.
It is slated for a later release. Personally, I think it will be a
fun project. If anyone’s interested in working on this, feel free
to comment on
Further details about Pantry
I’m not sure if Pantry is a topic people are interested in
hearing more about and using it in their own projects. For now, I’m
keeping the details relatively high-level in this post. If there's
a demand for more information, hit me up with questions and I can
put together another post answering them.
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