[Haskell-cafe] Compilers

[Daniel Fischer]

Am Sonntag, 30. November 2008 15:57 schrieb Eric Kow:
> Hi Daniel,
>
> On Sun, Nov 30, 2008 at 08:31:15 -0500, haskell-cafe-request at haskell.org 
wrote:
> > dafis at linux:~/lhc> darcs get --partial http://code.haskell.org/lhc
> > Invalid repository:  http://code.haskell.org/lhc
> >
> > darcs failed:  failed to fetch:
> > http://code.haskell.org/lhc/_darcs/inventory ExitFailure 1
> >
> > There's a hashed_inventory in lhc/_darcs, but no inventory.
> > Is that a darcs2 vs. darcs1 incompatibility and I'm just screwed or is
> > the repo broken?
>
> There are two issues here.  One is that the LHC repository is indeed a
> darcs 2 repository

Yes, and as Austin told me, it was updated to darcs-2 format yesterday or the 
day before (depending on time-zone), so one might just consider it bad 
timing, except

> and you appear to have darcs 1 on your machine.  I
> think upgrading to darcs 2 would be a very good idea, and I'm sure the
> darcs community would be happy to help you with this.

I am now a proud owner of darcs-2.1.2, the source distribution built without 
problems :), make test said "All tests successful!" three times :D
Sorry to deprive you of the pleasure of helping.

I had problems with a darcs-2 prerelease earlier, that's why I was pessimistic 
about getting darcs-2 to work on my old system, the binary wouldn't work 
because it needed newer libs than I have (and updating those would wreak 
havoc on other components), and the one from the darcs repo needed a newer 
autoconf than I have, yay for source releases.
>
> The second issue is that our forward-compatibility detector was likely
> buggy in darcs 1.0.9.  The response darcs 1.0.9 should have given you
> was something like this:
>
>   darcs failed:  Can't understand repository format: hashed
>   darcs failed:  Can't understand repository format: darcs-2

I've always found darcs' predictive powers somewhat lacking.
Seriously, it might be a good idea to have an error message like

darcs failed: Can't understand repository format, may be new format or broken.

because that would give a starting point for resolving the problem (darcs-2 
was conspicuous enough here that I thought of that possibility, but maybe 
darcs users not suscribed to the relevant lists wouldn't).
>
> Unfortunately, the relationship between hashed and darcs 2 repositories
> is slightly confusing.  Basically you need a darcs 2 client if you see
> hashed_inventory, but it does not necessarily mean there is an
> incompatibility.  I hope that the following snippet from the darcs 2.1.0
> release announcement can help clear this up:
>
> What should I do?
> -----------------
> Upgrade! Binary versions should be available shortly, either from your
> favourite package distributor or by third party contributors.

Please, do not drop source distributions anyone, binaries tend to work on a 
much smaller set of systems, source can build against more library versions.

Cheers,
Daniel