On 04/12/10 06:37, Mark Lentczner wrote:
Over on my blog, I've put up a proposal for changing the default layout of installed package pieces:
http://mtnviewmark.wordpress.com/2010/12/02/haskell-package-layout/
Thoughts?
As I understand it the main issue you bring up is that 1. It's not possible to install multiple versions of packages containing binaries, and/or documentation. 2. It's not possible to install the same version of a package, compiled with different compilers (or compiler versions), when that package contains binaries and/or documentation. and as a corollary 3. It IS possible to install multiple version of a package as long as it only contains a library. 4. It IS possible to install the same version of a package, compiled with different GHC versions, when that package only contains a library. Is this correct? I've come up against this limitation myself when packaging Hackage packages for ArchLinux in such a way that multiple version could be installed in parallel. That actually unearthed another limitation, one that you don't mention: the documentation index file, /usr/share/doc/ghc/html/libraries/index.html on my system. This file can be rebuilt with /usr/share/doc/ghc/html/libraries/gen_contents_index, but it only allows for one entry for each library. Further splitting up the hierarchy to better deal with multiple versions and configurations of a package being installed in parallel is probably a good thing. However, I don't think the split you make is very likely to be adopted. You suggest: $prefix -- /usr/local/haskell if --global, and ~/.cabal if --user $compiler $pkgid bin -- binaries lib -- libraries & .hi files include -- include files libexec -- private binaries share -- data files doc -- documentation html -- html doc man -- man pages Here are my arguments against this particular hierarchy: 1. I'd argue that Unix administrators expect $prefix to default to /usr/local. Defaulting to adding a new directory under /usr/local for haskell packages is unlikely to be appreciated. 2. As a distro packager I would have to make some considerable changes to the layout during the configure step, or alternatively create a considerable number of symlinks, to make things work (think of default $PATH, manpaths, etc). 3. I don't think your comment on per-interpreter directories for Python is true. AFAIK Python only uses that directory for modules, not for binaries and not for documentation. That would mean that Cabal's current behaviour matches what Python does. (Please correct me if my understanding of this is wrong.) Personally I would keep the top-level bits the same and instead insert bits in the lower levels: $prefix bin lib $compiler $pkgid include libexec $compiler $pkgid share $compiler $pkgid man doc $compiler $pkgid html Some comments on this: 1. Placing binaries in $prefix/bin increases the likelihood of things just working. Binaries from multiple versions/configurations of a single package can be handled by a suffix to the filename itself. It could be useful to be able to instruct Cabal to create a symlink from the basename to the full filename (basename-suffix) at install time. 2. Man pages can be dealt with in the same way as binaries, by using suffixes. I have to admit I'm not sure whether this is very standard, but it does seem to work. 3. Deleting stuff in this layout would be slightly more work than in yours, but not considerably more. Comments? /M -- Magnus Therning OpenPGP: 0xAB4DFBA4 email: magnus@therning.org jabber: magnus@therning.org twitter: magthe http://therning.org/magnus