Shipments in Cabal

[Krasimir Angelov]

2005/12/8, Isaac Jones <ijones at syntaxpolice.org>:
> Krasimir Angelov <kr.angelov at gmail.com> writes:
>
> > Hello Guys,
> >
> > I have started developing Shipments in Cabal.
>
> Awesome!  FWIW, you should probably take a look at the package
> dependency code in cabal-get, and you also might want to look at the
> new cabal-install tool, as I expect that when we ship a cabal w/
> cabal-install, people will use it a lot.  Although having shipments
> makes cabal-install less important.
>
> The smarts in cabal-get is that it checks to see what's already
> installed, and this might not really be desirable for a shipment
> (unless we want to have a flag for only installing the necessary
> stuff).
>
> BTW, could you open a new ticket or wiki page at the cabal wiki /
> ticket tracker:
> http://hackage.haskell.org/cgi-bin/trac/trac.cgi/report/3

Yes. I will.

> > It is working like it was discussed previously. When there are
> > multiple *.cabal files, in the directory where the Setup.lhs lies,
> > then they all will be build in dependency order.
>
> Are you using a temporary package-conf file?

It should but the dependency checking isn't implemented yet.

> > In order to keep the backward compatibility the package description
> > parser returns a list of PackageDescription. In the list there is
> > one element for the library and one element for each executable. The
> > package name for the executables is equal to the "executable" field
> > in the corresponding stanza in the package description file.
>
> I see.  You didn't want to break backward compatibility w/ the
> PackageDescription type?

The PackageDescription type is changed. The library and executables
fields are removed. There is a new field content :: PackageContent.
The PackageContent is something like:

data PackageContent
  = Library { ..... }
  | Executable { .... }

I just want keep backward compatibility in the package description file syntax.

> I kinda like this, package.cabalship (or whatever) might look like:
>
> shipment: shipmentname
> version: 1.1 -- inherited by the packages if they have no version num
> copyright -- ditto
>
> The only down side I see to this is that if version can be in the
> shipment, and need not be in the .cabal files, then the .cabal files
> are no longer stand-alone (they need the shipment file).

I would like to avoid the need for extra description files. The
version and copyright fields doesn't make sense for me providing that
each package has its own version, copyright, etc.

> > b> In HSQL I am using package names like: hsql, hsql-odbc, hsql-mysql, .....
> > One solution is to use the common prefix in the package names as
> > shipment name. When there is only one package, then the shipment name
> > will be equal to the package name. The advantage is that, when the
> > shipment name is encoded in the package name, then for the user it
> > will be easier to find the package sources.
> > The drawback is that we have to force some restriction on the package names.
>
> I don't really like the idea of forcing them to name their packages in
> a particular way.  For instance, you might have a package cabal but
> want an executable install-cabal.  We don't want to force people to
> use particular names for their binaries.
>
> > c> Another solution is to use the name of the top level directory. The
> > drawback is that the user can't rename the top level directory.
>
> Another simple idea is that we could add a shipment: field to the
> .cabal file.  This would cause some redundancy between .cabal files,
> but that's nicer than b> or c>.

I like the idea for "shipment" field since it is a light weight
solution. The redundancy is not high and I can't see any reason why we
shouldn't allow to have .cabal files from different shipments in one
directory. In this case the sdist command will simply create multiple
.tar.gz files. If the "shipment" field is missing then the default
value will be equal to $pkgid.


> Also, have you thought about how one might specify that they only want
> to operate on one part of the package (a single .cabal file?).  Maybe
> defaultSetup could take optional command-line option which is the
> .cabal file(s) to operate on, and if none are specified, then use
> *.cabal.
>
> This is where the cabal-get dependency code could come in handy.
> Let's say I have a shipment with A.cabal, B.cabal, and C.cabal where A
> depends on B and B depends on C.  I already have C installed for some
> strange reason, it would be nice to say:
>
> ./setup configure  A.cabal B.cabal
> ./setup build
> ./setup install
>
> and that should work just fine, because C is already installed.  OTOH,
> if you said:
>
> ./setup configure  A.cabal
> ./setup build
> ./setup install
>
> then setup should complain that you don't have B.

Yes. In Visual Haskell, I will need some way to specify that I want to
build only one of the packages.

Cheers,
  Krasimir