[Haskell-cafe] Recompiling Hackage to estimate the impact of a change [Was: StricterLabelledFieldSyntax]

[Ian Lynagh]

On Sat, Jul 25, 2009 at 11:25:12PM -0700, Donald Bruce Stewart wrote:
> johan.tibell:
> > 
> > In general, I think it would be a good idea to provide some statistics of how
> > many packages would break as the result of a backwards incompatible change.
> 
> Agreed. And it should be required as part of release processes for GHC.
> 
> Duncan has described the process of building large amounts of Hackage,
> 
>     http://blog.well-typed.com/2009/03/regression-testing-with-hackage/

That process requires too much effort. IIRC it took more than a day of
actual human time to get the package list set up etc, and requires you
to make some non-obvious decisions along the way.

I think a better process would be more along the lines of:

for p in $packages
    cabal install p
    rollback?

except smarter, so that it doesn't try to install packages that it has
already installed as a dependency of something else.


Thanks
Ian