Remove Setup.hs, use Setup.lhs only

[Duncan Coutts]

On Tue, 2006-11-28 at 18:28 +0000, Ross Paterson wrote: 
> On Tue, Nov 28, 2006 at 12:28:56AM +0000, Duncan Coutts wrote:
> > It's not clear to me that we need to have an extra field. I had
> > originally envisaged that cabal-setup would just find the right compiler
> > to build Setup.(l)hs and if there was none that it'd use defaultMain
> > (possibly without needing to compile any setup binary).
> 
> If there was a Setup.[l]hs, it wouldn't be correct to use defaultMain,
> would it?

Indeed, it would not.

If there's a Setup.[l]hs then we use that. If there isn't then we use
Distribution.Simple.defaultMain (either directly or indirectly via a
simple Setup.hs).

> > So do we really need a 'build-type:' field? Arn't there just two values
> > for it, 'Simple' and 'Custom' (since all others are just different
> > implementations of 'Custom')?
> 
> In that sense, there's only one value (Custom), but defaultMain is
> common, and a reasonable number of packages use
> 
> 	main = defaultMainWithHooks defaultUserHooks

which (bizarrely) is not the same as defaultMainWithHooks
defaultUserHooks, though it really should be.

> I had a value for Distribution.Make.defaultMain too (but I don't know
> if anyone uses that).
> 
> > Can't the Simple/Custom distinction be simply if the Setup.(l)hs is
> > present or not?
> 
> If you have a field, cabal-setup can avoid compiling Setup.[l]hs in the
> common cases.

Oh you mean that since people would want to be backwards compatible that
they would include a simple Setup.hs and then we loose the advantage of
not having to compile Setup.hs and thus having an extra field to say to
use simple even if there is a Setup.hs present is a benefit?

Yes, it is a benefit but it seems rather marginal to me. Remember that
we can't always avoid building a trivial Setup.hs anyway, since in the
case that cabal-setup was built with Cabal-x.y and the .cabal requests
cabal version x.y+1 then cabal-setup needs to build Setup.hs with the
later version of the Cabal lib and use that.

Duncan