[GHC] #1837: ghc-pkg should not accept unversioned depends

[GHC]

#1837: ghc-pkg should not accept unversioned depends
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    Reporter:  duncan        |       Owner:          
        Type:  bug           |      Status:  new     
    Priority:  normal        |   Milestone:          
   Component:  Build System  |     Version:  6.8.1   
    Severity:  normal        |    Keywords:          
  Difficulty:  Easy (1 hr)   |    Testcase:          
Architecture:  Multiple      |          Os:  Multiple
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 Historically ghc-pkg accepted a format where the "depends:" field did not
 require version numbers. Then ghc would just resolve it to some installed
 version. However now that ghc bakes in the version number to libraries
 when it compiles them it really crucial that a package gets linked with
 exactly the versions of packages it was built against. Allowing ghc-pkg to
 accept unversioned depends and resolving them to some random installed
 version is just asking for trouble.

 It's not too serious since Cabal always uses versioned depends, however I
 just noticed that older autoconf/automake build systems do not.

 So, in summary allowing undersioned depends is just asking for trouble and
 ghc-pkg should reject them.

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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1837>
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