draft proposal for relative paths in installed package descriptions

Simon Marlow marlowsd at gmail.com
Mon Jun 1 07:21:08 EDT 2009

On 29/05/2009 11:23, Duncan Coutts wrote:
> All,
> This is a draft proposal for a common mechanism for implementing
> relative paths in installed package descriptions.
> Comments and feedback are welcome. I'm cc'ing this to the cabal and
> ghc-users lists but let's keep the discussion on the libraries list.
> There has been some discussion of this issue on the cabal and ghc-users
> list, but it's a relatively long thread and the idea has evolved
> somewhat so this is an attempt to present the proposal clearly.
> Proposal
> ========
> This proposal is an extension to the Cabal spec section 3
> http://haskell.org/cabal/proposal/x272.html
> Motivation
> ----------
> Being able to have relative paths in the installed package description
> is useful as it makes it possible to construct relocatable
> (prefix-independent) package installations. This is useful when
> distributing compilers along with packages and there may be other uses.
> This proposal does not require that all paths are relative. It is still
> perfectly ok to use absolute paths where appropriate.  It just adds an
> option to use relative paths.
> The aim is for a single simple specification that any compiler can
> implement and have the tools work uniformly, rather than ad-hoc
> implementations for each compiler.
> Details
> -------
> In the installed package description, we will allow paths that begin
> with the variables ${pkgroot} or ${pkgrooturl}. For example:
> library-dirs: ${pkgroot}/foo-1.0
> haddock-html: ${pkgrooturl}/doc/foo-1.0

Seems fine to me.  So basically this just replaces GHC's undocumented 
$topdir feature?


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