[GHC] #16259: Hadrian does not work with a cabal v2-installed "Happy"

[GHC]

#16259: Hadrian does not work with a cabal v2-installed "Happy"
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        Reporter:  RolandSenn        |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Build System      |              Version:  8.6.3
  (Hadrian)                          |
      Resolution:                    |             Keywords:
Operating System:  Linux             |         Architecture:
 Type of failure:  Building GHC      |  Unknown/Multiple
  failed                             |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by snowleopard):

 * cc: NeilMitchell (added)


Comment:

 > a simple way to workaround this is inject a constraint to prevent
 Setup.hs scripts from using an unreleased version of lib:Cabal, via e.g.

 @hvr: The fact that Hadrian currently depends on the in-tree Cabal library
 has proven to be both slow and fragile. Neil and I have recently been
 thinking that we should revert to depending on a stable release of Cabal
 instead.

 Pros:

 * This will make Hadrian faster to build if the (stable) Cabal library is
 shared with other projects on the same machine.

 * We don't need to adapt/rebuild Hadrian every time the in-tree Cabal
 library is changed. We will upgrade to a new Cabal version only when need
 be.

 * This will hopefully allow us to avoid issues like the one described in
 this ticket.

 Cons:

 * We will not be able to parse GHC's `.cabal` files if they use bleeding-
 edge features of Cabal. And arguably, they shouldn't.

 Any thoughts on this? I could spawn this into a separate ticket.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16259#comment:4>
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