Re: Gearing up for a cabal-install-1.16.0 release

On 01/10/2012 09:26, Duncan Coutts wrote:

On 1 October 2012 04:21, Johan Tibell wrote:

...

Hi,

I don't want to hold up the release on this issue if it needs more discussion. I'd like to make another Cabal/cabal-install release before end of the year (probably around GHC's release timeline), to include the sandbox stuff once done. Would it be OK to wait until then with these two patches?

I think these specific patches do not need discussion now, here's why: the feature comes in two parts, server and client, the bulk of the feature is the server side part which is not implemented yet. There's plenty of time for more discussion of the feature in general before we start actually using it. But if we decide it's ok, then we have to wait even longer to start using it. We can deploy new server side code quickly, but not client side code. If we decide it's not ok, then we don't make use of the feature server-side and then we rip out the client code. So that's why I want to get the client code in now, in advance of the server side implementation.

Also note, I have discussed this before with several people (and I think on this list too, a couple years back). So Bryan didn't see it, but it's not like I'm inventing this crazy idea from nowhere and forcing it on people. I'm very happy to discuss the details again, but that's independent of these two patches.

Forgive me if I'm being stupid, but why can't the feature be implemented entirely on the server? That is, when the dependencies are updated by some as-yet-unspecified mechanism on the server, a complete new version of the package is generated and added to the index. A new tarball would be generated on the server, by replacing the .cabal file in the previous tarball. The behaviour would be exactly as if a new version had been uploaded, but it is all done by Hackage, using some pre-agreed version numbering policy. This would eliminate the problems of having invisible metadata floating around, and having 'cabal unpack' doing clever magic behind your back. The index would remain a pure function of the set of tarballs. Cheers, Simon