[Haskell-cafe] is there a way to patch the build-depends line of a cabal file without breaking backwards compatibility?

[Thomas Hartman]

> Take a look at the Cabal.cabal file, how this is solved, atm.

where is this, how can I take a look at it?

> The next release of Cabal (and the current HEAD) supports  conditionals

I couldn't install head, but since I'm running 6.7, do I already have it?

hartthoma at linuxpt:~/installs/cabal-head/cabal>runghc Setup.lhs configure

Distribution/Simple/InstallDirs.hs:267:36:
    Not in scope: `dropDrive'

hartthoma at linuxpt:~/installs/cabal-head/cabal>ls -l `which ghc`
lrwxrwxrwx 1 root root 31 2007-08-20 11:08 /usr/local/bin/ghc -> 
/usr/local/bin/ghc-6.7.20070816


hartthoma at linuxpt:~/installs/cabal-head/cabal>ghc-pkg list | grep -i cabal
    Cabal-1.1.7

>  Please also note that this might not be the 
> best way to use the new features;  as I suggested in another thread, 
> simulating base-1.0 on systems with base-2.0 is probably best handled 
> with a base.cabal file that imports base-2.0, old-time, etc. and re- 
> exports all imported modules to get a "virtual" base-1.0.

I'm interested in seeing how this works, but I couldn't find that other 
thread.

Where is the documentation for the new functionality in cabal head, or do 
you just have to read the source code for now?

thanks, t




Thomas Schilling <nominolo at googlemail.com> 
08/20/2007 01:37 PM

To
Thomas Hartman/ext/dbcom at DBAmericas
cc
haskell-cafe <haskell-cafe at haskell.org>
Subject
Re: [Haskell-cafe] is there a way to patch the build-depends line of a 
cabal file without breaking backwards compatibility?







On 20 aug 2007, at 18.37, Thomas Hartman wrote:

>
> cafe, is there a way to patch the build-depends line of a cabal 
> file without breaking backwards compatibility?
>
> I just patched HDBC head to compile under ghc 6.7. Unfortunately it 
> now won't compile in 6.6.1.
>
> is there a way for build-depends to detect which version of ghc 
> you're on?
>
> also I seem to recall that -fglasgow-exts was deprecated under 6.7. 
> is there a better way to beat back the error message below than this?
>

The next release of Cabal (and the current HEAD) supports 
conditionals to test for flags, os/arch, and implementation 
(+version).  Note that the problem isn't the GHC version, but the new 
base version, in which the old base was split up into smaller 
packages, so we have something roughly like:  base-1.0 = base-2.0 + 
bytestring + old-time + mtl.  Take a look at the Cabal.cabal file, 
how this is solved, atm.  Please also note that this might not be the 
best way to use the new features;  as I suggested in another thread, 
simulating base-1.0 on systems with base-2.0 is probably best handled 
with a base.cabal file that imports base-2.0, old-time, etc. and re- 
exports all imported modules to get a "virtual" base-1.0.

/ Thomas




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