[Hackage] #342: Allow automatic resolving of conditionals on more than just build-depends

[Hackage]

#342: Allow automatic resolving of conditionals on more than just build-depends
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  Reporter:  duncan         |        Owner:                
      Type:  enhancement    |       Status:  new           
  Priority:  normal         |    Milestone:                
 Component:  Cabal library  |      Version:  HEAD          
  Severity:  normal         |   Resolution:                
  Keywords:                 |   Difficulty:  hard (< 1 day)
Ghcversion:  6.8.2          |     Platform:                
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Comment (by EricKow):

 As requested by Duncan, I'm noting here an example of how this would be
 used by a large application.

 To support the widest user base possible, darcs allows the user to use
 either libcurl, libwww or the HTTP package for fetching files.  We also
 have logic such as "if the version of libcurl < 7.19, do not compile in
 any http support; if the version is > 7.19, but < 7.19.1, compile in HTTP
 pipelining support, but don't enable it because pipelining support in that
 version is buggy behind proxy servers; otherwise if libcurl is really new,
 enable HTTP pipelining by support"

 This kind of logic we normally store in an autoconf test, but it would be
 nice if cabal could somehow support it.  At the moment, our cabal file
 defaults to using curl, and disables HTTP pipelining support altogether.
 The user has to specify -f curl-pipelining to enable it.

-- 
Ticket URL: <http://hackage.haskell.org/trac/hackage/ticket/342#comment:4>
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