[GHC] #11557: Unbundle Cabal from GHC

[GHC]

#11557: Unbundle Cabal from GHC
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           Reporter:  ezyang         |             Owner:
               Type:  task           |            Status:  new
           Priority:  normal         |         Milestone:  8.2.1
          Component:  libraries      |           Version:  8.1
  (other)                            |
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 Recently, Duncan made it so that GHC proper does not depend on Cabal (so
 it is just ghc-pkg that is the user-facing executable which links against
 Cabal). We should now seriously consider unbundling Cabal from GHC, so
 that the default global database we provide does NOT include Cabal.

 Pros:

 * Distributions will be more likely to take point version releases to
 Cabal, as they no longer have to finesse updating Cabal without updating
 GHC as they have now

 * Stack is (improperly) coupling the version of Cabal they build with the
 release of GHC; while they should fix this, unbundling Cabal would also
 give them more flexibility with picking LTS packages.

 Cons:

 * Bootstrapping Cabal/cabal-install becomes modestly harder.  Fortunately,
 cabal-install is already pretty obnoxious to bootstrap, so SOP is to just
 distribute binaries for this, in which case things are as easy as before.

 * We wouldn't be strictly adhering to the Cabal spec, which requires that
 the compiler always be able to build the Setup executable.

 * ghc-pkg would have to be statically linked

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11557>
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