[GHC DevOps Group] Release policies

Gershom B gershomb at gmail.com
Tue Dec 19 17:28:43 UTC 2017

Good questions. In my below proposal I think I made an error in naming
things. I checked back at the wiki page for the new release calendar
schedule: https://ghc.haskell.org/trac/ghc/wiki/WorkingConventions/Releases/NewSchedule

Based on that, what I was calling "freeze" is really just cutting the
branch. But it isn't intended as a full freeze. That happens 3 months
before release. The "feature freeze" in that calendar only comes with
the first RC, 1 month before release.

I think that this timing still works with the proposal I have however
-- bundled libs branch when GHC branches (T-3), and cut releases when
GHC cuts the first RC (T-1). For bundled libs, I think we'd want to
treat that branch (T-3) as closer to a feature freeze.

However, and here I disagree with Manuel, I think there's plenty of
reason to _not_ cut release versions of libs at the time of the T-3
branch. In particular, due to the coupling, this may cause trouble if
there are cross-cutting changes that need to be implemented for the
sake of GHC working properly over the three month duration of the
alpha. If there's a feature in a library designed to work in
conjunction with a change in GHC, and that change in GHC needs to be
altered in the course of the alpha (which may not be uncommon -- bug
testing can often reveal such things) then it is likely the library
may need to be changed too. I don't see any concrete goal solved in
making this process significantly more difficult. I thought Moritz'
examples in this thread were very revealing with regards to such
possibilities. It is not clear what cost function the stronger
proposal is trying to optimize for.

If it is that we want a branch that is "always ready to be cut for
release" (why? is such a thing even possible anytime in the
foreseeable future?), one middle ground may be to cut _candidate_
releases of bundled libs on branch (T-3).


On Tue, Dec 19, 2017 at 10:12 AM, Michael Snoyman <michael at snoyman.com> wrote:
> Thanks for spelling this out Gershom. Reading it through, here are my
> questions:
> 1. What's the definition of "feature freeze"? Does it mean API stability?
> Does it mean not code changes at all except to fix a bug? Are performance
> fixes allowed in that case?
> 2. What's the minimum time between GHC cutting a feature-freeze branch and
> the first release candidate? And the minimum time between first release
> candidate and official release? Obviously, if each of these is 1 week (which
> I can't imagine would be the case), then these libraries could cut a
> feature-freeze branch after the official release, which obviously isn't
> intended. I apologize if these timings are already well established, I'm not
> familiar enough with GHC release cadence to know.
> I can't speak to GHC development itself, but from a downstream perspective,
> this sounds like the right direction.
> On Mon, Dec 18, 2017 at 9:41 PM, Gershom B <gershomb at gmail.com> wrote:
>> Let me try to formulate a synthetic policy as per Simon's request:
>> Policy:
>> Bundled library maintainers agree to the following:
>>   1) When GHC cuts a feature-freeze branch, they too (if anything has
>> changed) cut a feature-freeze branch within two weeks at the maximum
>> (ideally sooner), to be included in the main GHC freeze branch. If
>> they do not do so, the last released version will be included instead.
>>   2) When GHC releases the first release candidate, maintainers (if
>> anything has changed) release new versions of their packages, to then
>> be depended on directly in the GHC repo. All submodules are then
>> replaced with their proper released versions for GHC release.
>> This policy can be enforced by GHC hq as part of the release process
>> with the exception of a case in which there's coupling so that a new
>> GHC _requires_ a new submodule release, and also the maintainer is not
>> responsive. We'll have to deal with that case directly, likely by just
>> appealing to the libraries committee or something to force a new
>> release :-)
>> Motivation:
>> This should help address multiple issues: 1) holdup of ghc on other
>> releases. 2) lack of synchronization with ghc and other releases. 3)
>> low lead-time for people to adapt to API changes in forthcoming
>> library releases tied to ghc releases. In particular, because Cabal is
>> part of this policy, it should help circumvent the sorts of problems
>> that led to this thread initially. Further, because this only applies
>> to freeze/release branches, it should not slow down
>> rapid-implementation of cross-cutting changes more generally.
>> Cheers,
>> Gershom
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