[Hackage] #789: build-depends on packages that provide no library

[Hackage]

#789: build-depends on packages that provide no library
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  Reporter:  duncan              |        Owner:      
      Type:  defect              |       Status:  new 
  Priority:  normal              |    Milestone:      
 Component:  cabal-install tool  |      Version:  HEAD
  Severity:  normal              |     Keywords:      
Difficulty:  unknown             |   Ghcversion:      
  Platform:                      |  
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 It is possible to list build-depends on packages that have just an
 executable and no library. Currently the behaviour of cabal-install does
 not consider this and it will allow such packages to be pulled in as
 dependencies. It leads to problems however because the non-lib package
 never gets registered with ghc-pkg and so it leads to re-install loops.

 The solution is for cabal-install to not consider exe-only packages to be
 valid for satisfying a build-depends requirement. It should produce a
 suitable error message.

 Note that it must take into account the posibility that a newer or older
 version of a package may switch from exe only to exe+lib or just lib, or
 indeed vica versa.

 We should mark exe-only versions of the package as excluded with a reason.
 Then if the dep is not satisfiable then we can explain why all the
 excluded ones were excluded (ie due to not exposing a lib).

-- 
Ticket URL: <http://hackage.haskell.org/trac/hackage/ticket/789>
Hackage <http://haskell.org/cabal/>
Hackage: Cabal and related projects