[Hackage] #392: Use the constraint solver for cabal configure

[Hackage]

#392: Use the constraint solver for cabal configure
---------------------------------+------------------------------------------
  Reporter:  duncan              |        Owner:                   
      Type:  enhancement         |       Status:  new              
  Priority:  normal              |    Milestone:  cabal-install-0.6
 Component:  cabal-install tool  |      Version:  1.2.3.0          
  Severity:  normal              |     Keywords:                   
Difficulty:  normal              |   Ghcversion:  6.8.3            
  Platform:                      |  
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 Currently `cabal install` and `cabal upgrade` use the constraint solver to
 select the dependencies while `cabal configure` just selects the highest
 version of each package.

 That means it sometimes picks bad combinations where `cabal install` would
 do something smarter. It also means it does not use preferences like `base
 < 4`.

 However for `cabal configure` it's important that the solver not fail and
 prevent configuring at all. If the solver cannot find a consistent
 solution we should probably warn and fall back to the existing behavior.
 We may also want to prevent `cabal configure` from picking anything other
 than the current installed packages. Though again that's likely to
 increase the chance of failure.

 Perhaps if there is no solution for the current installed packages then it
 should check if there would be a solution if we allowed re-installs and if
 so say so in the warning message. If not fall back to the highest versions
 of everything as now.

-- 
Ticket URL: <http://hackage.haskell.org/trac/hackage/ticket/392>
Hackage <http://haskell.org/cabal/>
Hackage: Cabal and related projects