[Gtk2hs-devel] move Gtk2HsSetup.hs to gtk2hs-buildtools

[Axel Simon]

Dear Libraries,

this message is on shortcomings of cabal with respect to automatically  
installing the gtk package which (a) depends on a package that  
contains only build tools (i.e. only binaries) and (b) has a big  
custom Haskell file Gtk2HsSetup.hs that Setup.hs has to import (and  
which is required in any package in the Gtk2Hs suite). This file is  
copied into every package of the Gtk2Hs suite which is a pain to  
maintain.

On 25.11.2010, at 10:50, Lazycat Manatee wrote:

> ---------- Forwarded message ----------
> From: Jens Petersen <petersen at haskell.org>
> Date: 2010/11/25
> Subject: Re: [Gtk2hs-devel] move Gtk2HsSetup.hs to gtk2hs-buildtools
> To: Andy Stewart <lazycat.manatee at gmail.com>
>
>
>> Jens Petersen <petersen at haskell.org> writes:
>>
>>> I suggest moving Gtk2HsSetup.hs into a library, it could be part
>>> of gtk2hs-buildtools perhaps.  How about it?
>> It can't work.
>>
>> Because we need Gtk2HsSetup.hs generate Signals.chs and Types.chs  
>> *before*
>> any cabal depend check.
>
> Hmm I haven't tested but don't really understand.
> You mean it will break builds with cabal-install?
> Doesn't gtk2hs-buildtools already do that? :)
>

Yes, but these are two separate show-stoppers:

a) the gtk2hs-buildtools contains only binaries. It does not register  
as a package with ghc. Thus, if we make the gtk package depend on  
gtk2hs-buildtools, cabal would complain that (even after installing  
gtk2hs-buildtools) the gtk2hs-buildtools library is not there

b) putting Gtk2HsSetup.hs in either gtk2hs-buildtools or any other  
library means that ./Setup.hs has to run to realize that this library  
is missing and that it needs to be downloaded. However, ./Setup.hs  
cannot be run because it imports Gtk2HsSetup.hs which is not yet  
available.

I don't know if (b) can be solved by e.g. conditionally importing  
Gtk2HsSetup.hs if it is there and only installing libraries and re- 
invoking Setup.hs one this is done. This is a common trick in  
Makefiles, e.g. one could call make recursively to first build  
dependencies. Any suggestions welcome.

Regards,
Axel