Hadrian does not work with a cabal v2-installed "Happy"

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changed title from Hadrian does not work with a cabal v2-installed "happy" to Hadrian does not work with a cabal v2-installed "Happy"

changed the description

Ok, so the problem here is that happy gets demoted into an inplace package (and this basically means that the resulting executable can't be invoked without setting a couple of env-vars, which cabal {run,exec} would do -- but if you don't invoke it that way you'd be responsible for doing this... long story), because it picked up a local dependency, namely the intree-Cabal for its setup-depends; 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.

diff --git a/hadrian/cabal.project b/hadrian/cabal.project
index 176d1ee..d8e5e79 100644
--- a/hadrian/cabal.project
+++ b/hadrian/cabal.project
@@ -1,2 +1,4 @@
 packages: ./
           ../libraries/Cabal/Cabal/
+
+constraints: setup.Cabal < 2.5

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.

added ghc build failure label

I experienced the same issue with ghc-8.8.1-alpha1. After adding constraints: setup.Cabal < 2.5, I get a different error:

  at error, called at src/Development/Shake/Internal/Rules/File.hs:179:58 in shake-0.17.8-430f6b34c1956f8d4c773995ef66539a88fd36bb9b90bf5a1fd4fe477bdf1f37:Development.Shake.Internal.Rules.File
* Raised the exception:
Error, file does not exist and no rule available:
  /home/fumieval/hs/ghc/hadrian/dist-newstyle/build/x86_64-linux/ghc-8.6.2/happy-1.19.9/build/happy/happy

added Pnormal label

@snowleopard Any updates on using the out-of-tree Cabal in Hadrian? Sounds like a great idea to me.

@int-index OK, let me give this a try.

assigned to @snowleopard

mentioned in merge request !1876 (closed)

Here is the MR: !1876 (closed)

@RolandSenn !1876 (closed) has been merged. Does it fix this issue?

@snowleopard @hsyl20

Does it fix this issue?

Yes! and thanks! I close the issue.

@fumieval Please feel free to reopen, if your issue is not solved.

closed

Hadrian does not work with a cabal v2-installed "Happy"

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