On Fri, Jul 23, 2010 at 04:58, Mark Wotton <mwot...@gmail.com> wrote: > On Fri, Jul 23, 2010 at 12:33 PM, wren ng thornton <w...@freegeek.org> wrote: >> Magnus Therning wrote: >>> >>> On Thu, Jul 22, 2010 at 11:52, Ross Paterson <r...@soi.city.ac.uk> wrote: >>>> >>>> On Thu, Jul 22, 2010 at 11:31:21AM +0100, Magnus Therning wrote: >>>>> >>>>> On Thu, Jul 22, 2010 at 10:59, Ross Paterson <r...@soi.city.ac.uk> >>>>> wrote: >>>>>> >>>>>> Magnus is building by directly running the Setup.hs himself, which >>>>>> ignores >>>>>> the Build-Type. To get cabal-install to use his Setup.hs, the >>>>>> Build-Type >>>>>> must be set to Custom. >>>>> >>>>> Oh, why*2? >>>>> >>>>> Why is the header there if it's not used by Cabal, and why does cabal >>>>> care? >>>> >>>> The field allows cabal to avoid compiling the Setup.hs in this case. >>>> It might also be used by other tools, e.g. one might only trust Simple >>>> packages. Not all fields are used by all tools, and several of them >>>> do not affect the operation of the library (e.g. Home-page). >>> >>> All right, so why would cabal want to avoid compiling the Setup.hs? >>> >>> Of course this behaviour of cabal's means that I in the future will use >>> *Custom* >>> all the time, since I otherwise have to remember this surprising feature >>> of a >>> tool I never use. Is there any reason *not* to do this? >> >> The main reason I could think of to avoid compiling it is for performance >> reasons. I'm not sure how compelling that is, but... >> >> As for why not to always use Custom, as mentioned there are cabal-aware >> tools out there besides cabal-install. For these other tools, there is a big >> difference between Simple and Custom. With Simple we (ideally) already know >> all the semantics of what Setup.hs does, and so we can wire that into our >> tools. With Custom we're forced into the position of doing Haskell source >> analysis since we now have to discover the semantics of an arbitrary Turing >> machine. That's a very high wall to climb if you're just wanting to write a >> simple tool for doing some kind of package analysis. >> >> (I don't think the behavior is surprising since I interpret Simple to mean >> that the Setup.hs file is unused/optional. Though clearly YMMV) > > > Ah, this clears up one of my bugs. > > Perhaps cabal should print a warning if you have a Setup.hs file, > _and_ try to use Simple? It'd at least give the hint that they're > unhappy together.
I don't like that idea. I don't use cabal, so I always need a Setup.hs whether the Build-Type is Simple or Custom. This suggestion would also force some tools that don't care about Build-Type (they just use the Setup.hs irrespective of Build-Type) to start caring. /M -- Magnus Therning (OpenPGP: 0xAB4DFBA4) magnus＠therning．org Jabber: magnus＠therning．org http://therning.org/magnus identi.ca|twitter: magthe _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
