I have been thinking about the location of installed Haskell package files on
Mac OS X. The choice of location affects:
GHC & other Haskell implementations
Haskell Platform
Cabal & cabal-install
Haddock
If all those agreed on directory locations and layouts, I think the state of
Haskell on Mac OS X would be nicer for users. In particular, my hope is for
users to end up with an automatically complete Haddock documentation
incorporating everything they install.
1) Packages the user installs --global
I noticed that the default location for global installation with cabal is on
Mac OS X is /usr/local:
install-dirs global
-- prefix: /usr/local
This then intermingles all the Haskell package files along with all sorts of
other things that live in /usr/local and environs. While this is arguably
convenient for executables that end up in /usr/local/bin (in most people's
PATH), it does make things less than tidy, and harder to clean up.
Taking a cue from the various preinstalled language systems on Mac OS X, up
over in /Library might be a better place:
Python puts installed packages in:
/Library/Python/<version>/site-packages
Ruby puts installed packages in:
/Library/Ruby/Gems/<version>
/Library/Ruby/Site/<version>
Java appears to use
/Library/Java/Extensions
and has a link to the packages that come the framework as:
/Library/Java/Home
Perl put installed packages in:
/Library/Perl/<version>
I suggest that the default place for global installs on Mac OS X be:
/Library/Haskell/
Since cabal already by default interposes the compiler version into the lib
dir, path, there doesn't appear to be a need to put a <version> dir level near
the top.
2) Structure of package pieces
I notice that cabal/cabal-install's default layout of where a package's pieces
go, and GHC's layout of its base packages don't agree. Further,
cabal/cabal-install's are not set up so that one can easily delete an installed
package without hunting down its parts.
cabal/cabal-install defaults the parts as follows:
executables: --prefix--/bin
libraries: --prefix--/lib/--pkgid--/--compiler--
data: --prefix--/share/--pkgid--
doc: --prefix--/share/doc/--pkgid--/
html: --prefix--/share/doc/--pkgid--/html
That's at least four directories you need to hunt down if you want to clean out
a package, and rummaging through bin to figure out which things to remove. (Not
to mention libexec, which isn't used by any packages on my system, so I can't
say where it goes...)
GHC/Haskell Platform use a different layout:
executables: --prefix--/bin
libraries: --prefix--/lib/--compiler--/--pkgid--
data: --prefix--/share/--pkgid--
doc: --prefix--/share/doc/ghc/libraries/--pkgid--/
html: --prefix--/share/doc/ghc/libraries/--pkgid--/
I think it best if everything for a package is in one place - making removal
very easy:
executables: --prefix--/packages/--pkgid--/bin
libraries: --prefix--/packages/--pkgid--/lib/--compiler--
data: --prefix--/packages/--pkgid--/share
doc: --prefix--/packages/--pkgid--/doc
html: --prefix--/packages/--pkgid--/doc
I put the "packages" level at the top, so that other things, like a master
Haddock index dir could be put easily directly under the prefix.
3) Symlinks for binaries
This does suggest that it would be nice for the symlink-bindir facility (is
that in cabal itself, or added by cabal-install?) to have a version for
--global installs. Users could then either set something like:
symlink-global-bindir: /usr/local/bin
in .cabal/config.
Or
symlink-global-bindir: /Library/Haskell/bin
and then put that in their PATH
4) Quick access to the Framework
I like Java's convenience link 'Home', and suggest that
/Library/Haskell/GHC
be a symlink to where the framework's package files are stored:
/Library/Frameworks/GHC.framework/Versions/Current/usr/
Other implementations could use the same idea.
Having this here would also (I suspect) help in getting Haddock to be able to
find all the bits needed to generate a comprehensive index.
Thoughts? I'd be happy to help by supplying patches for various tools to
normalize all this on some agreed upon layout. I admit that I'm a bit unclear
where the directory choices are being made: Haskell Platform's build process,
or GHC's? Cabal's defaults or cabal-install's? And then clearly parts of
Haddock. Given the number of tools that need to agree, seems best that we hash
it out (here or in the wiki) first, before making patches.
- Mark (mtnviewmark)
Mark Lentczner
http://www.ozonehouse.com/mark/
[email protected]
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