Advance notice that I'd like to make Cabal depend on parsec

Administrator admin at
Thu Mar 14 16:22:59 CET 2013

This GHC dependency on Cabal is putting a rather troubling constraint
in Cabal's evolution, which in my opinion is a serious problem. When I
first took a look at the dependencies between GHC and Cabal I found it
a bit strange that GHC would depend on Cabal as I would expect GHC to
be as low in the dependency tree as possible to avoid exactly these
kinds of problems.

These GHC dependencies on Cabal are in fact small (see
for a summary) and with a little bit of refactoring it would be
possible to split these dependencies into a very small shared package
with minimal or no further dependencies. This would liberate Cabal to
make the necessary refactoring.

IMHO, the addition of these new dependencies to Cabal should go
together with splitting the GHC-Cabal shared dependencies into a
separate package so that there would be no additional coordination
needed from then on between these two development efforts (except when
dealing with this new package).

On Thu, Mar 14, 2013 at 12:12 PM, Duncan Coutts
<duncan.coutts at> wrote:
> On Thu, 2013-03-14 at 16:06 +0100, Gregory Collins wrote:
>> On Thu, Mar 14, 2013 at 3:53 PM, Duncan Coutts <duncan.coutts at
>> > wrote:
>> > Hi folks,
>> >
>> > I want to give you advance notice that I would like to make Cabal depend
>> > on parsec. The implication is that GHC would therefore depend on parsec
>> > and thus it would become a core package, rather than just a HP package.
>> > So this would affect both GHC and the HP, though I hope not too much.
>> +1 from me, although the amount of potential knock-on work might be
>> discouraging. The current cabal-install bootstrap process (which is
>> currently pretty easy and is necessary at times) will get a bunch more deps
>> as a result of this change, no?
> Yes it will, but given that we do have a script it's not too bad I
> think. And overall I think its worth it to have the better error
> messages, performance and memory use. Do you have any idea how slow it
> is to parse all the .cabal files on hackage, and how much memory that
> takes? You'd be horrified :-)
> Duncan
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