[GHC] #8244: Removing the Cabal dependency

[GHC]

#8244: Removing the Cabal dependency
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        Reporter:  nh2               |            Owner:
            Type:  bug               |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  Compiler          |          Version:  7.6.3
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by ydewit):

 Yes, having the GHC build system depend on Cabal is harmless: the real
 issue, imo, is GHC modules directly depending on Cabal modules to handle
 package description/parsing/serialization functionality.

 I also agree that it doesn't make sense to extract a subset of Cabal just
 to be used by the build system: that wouldn't add anything and possibly
 even make it harder to build GHC.

 However, I do not follow why would the 60+ Cabal modules and the full
 Cabal source tree would still need to stick around. If only the GHC build
 system depends on Cabal for building GHC libraries, why can't Cabal be
 just a pre-requisite to building GHC in the same way that a recent version
 of GHC is a pre-requisite to building stage0?

 The way I am seeing this, once this direct dependency from GHC to Cabal is
 removed, GHC build system can simply state as a pre-requisite a range of
 Cabal versions supported. And If we do a good job extracting a minimal set
 of modules for this shared package that has no Cabal or GHC specific
 implementation details, then this shared package will rarely change and
 this range of supported Cabal versions will be quite wide.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8244#comment:10>
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