We seem to be circling ever closer to consensus here! Yay!

Indeed!  Good :-)

However, I’m not getting the bit about API changing vs non-API changing.

Firstly I don’t know which APIs are intended.  The GHC API is essentially GHC 
itself, so it changes daily.  Maybe you mean the base package?  Or what?

I suspect you mean that a “non-API-changing” release absolutely guarantees to 
compile any package that compiled with the previous version.  If so, that is a 
very strong constraint indeed. We do observe it for patch releases for GHC (e g 
7.6.2 should compile anything that 7.6.1 compiles).  But I think it would be 
difficult to guarantee for anything beyond a patch release.  Every single 
commit (and the commit rate is many/day) would have to be evaluated against 
this criterion.  And if it failed the criterion, it would have to go on a 
API-breaking HEAD. In effect we’d have two HEADs.  I can’t see us sustaining 
this.  And I don’t yet really see why it’s necessary.  If you don’t want an 
API-breaking change, stick with the patch releases.

So, we have a channel for non-API-breaking changes already: the patch releases. 
 So that means we already have all three channels!

·        Haskell Platform

·        Patch-level releases

·        New releases

if that’s so, all we need is better signposting.   And I’m all for that!

Have I got this right?

Simon

From: Mark Lentczner [mailto:mark.lentcz...@gmail.com]
Sent: 09 February 2013 17:48
To: Simon Marlow; Manuel M T Chakravarty; Johan Tibell; Simon Peyton-Jones; 
Mark Lentczner; andreas.voel...@gmail.com; Carter Schonwald; 
kosti...@gmail.com; Edsko de Vries; ghc-d...@haskell.org; glasgow-haskell-users
Subject: Re: GHC 7.8 release?

We seem to be circling ever closer to consensus here! Yay!

I think the distinction of non-API breaking and API breaking release is very 
important. Refining SPJ's trifecta:

Haskell Platform comes out twice a year. It is based on very stable version of 
GHC, and intention is that people can just assume things on Hackage work with 
it. These are named for the year and sequence of the release: 2013.2, 2013.2.1, 
2013.4,...

Non-API breaking releases can come out as often as desired. However, the 
version that is current as of mid-Feb. and mid-Aug. will be the ones considered 
for HP inclusion. By non-API breaking we mean the whole API surface including 
all the libraries bundled with GHC, as well as the operation of ghc, cabal, 
ghc-pkg, etc. Additions of features that must be explicitly enabled are okay. 
Additions of new APIs into existing modules are discouraged: Much code often 
imports base modules wholesale, and name clashes could easily result. These 
should never bump the major revision number: 7.4.1, 7.4.2...

API breaking releases happen by being released into a separate channel when 
ready for library owners to look at them. This channel should probably go 
through several stages: Ready for core package owners to work with, then HP 
package owners, then all package owners. I'd imagine this is a several month 
process. At the end of which, the release can go into the main channel. Such a 
merge shouldn't happen more than once a year... I think even once every two 
years is fine (!) To avoid confusion, I'd suggest that while in the separate 
channel, these release be named with odd number: 7.9, 7.11,..., and when moved 
to the main channel renamed to even: 7.10, 7.12...

This idea of three channels needs to be much more clearly communicated. The 
warning on the download page is a failure: Googling "ghc" takes you to the home 
page of GHC which immediately trumpets the "Lastest News" of a release of GHC 
7.6.2. Once a user has read that and decided to download, then "STOP!" box is 
a) going to be skipped as they scan for the download link, and b) if read and 
followed, causes the "WTF? Why is HP so back rev?" So we need to change the 
front page so that the three channels are clearly communicated and targeted at 
the right users.

- Mark

(BTW: The first few links on the GHC web site are out of date: The second nav 
link is to a survey that is 7 years old. The License page is 8 years out of 
date. The FAQ is over a year old.)

On Sat, Feb 9, 2013 at 8:24 AM, Ian Lynagh 
<i...@well-typed.com<mailto:i...@well-typed.com>> wrote:
On Sat, Feb 09, 2013 at 12:06:12PM +0000, Simon Marlow wrote:
>
> As a straw man, let's suppose we want to do annual API releases in
> September, with intermediate non-API releases in February.
That's a non-API release 5 months after the API release.

6.10.2 was 5   months after 6.10.1 (.3 was 1 month later, .4 a further 2)
6.12.2 was 4   months after 6.12.1 (.3 was 2 months later)
 7.0.2 was 3.5 months after  7.0.1 (.3 was 1 month later, .4 a further 3)
 7.2.2 was 3   months after  7.2.1
 7.4.2 was 4   months after  7.4.1
 7.6.2 was 4.5 months after  7.6.2

so if we do non-API releases, then perhaps it would make sense to stop
doing minor releases (unless a release turns out to just be broken).


Thanks
Ian

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