Hspec not building on GHC 9.4.2 due to dependency on ghc about hspec

[Mikolaj]

I think this line means that the package depends on boot non-upgradable package ghci that happens to link against transformers==0.5.6.2, so you have to use that version of transformers, period. The tickets I linked above may shed some more light on what I wrote or prove it's incorrect altogether. I remember there is an effort (a GHC ticket, I think) to make non-upgradable package upgradable. It may be linked inside the tickets above.

[sol]

@PilchardFriendly thanks for reporting this. The ghc package comes with GHC. It cannot be built from source. The same is true for other packages, most notably base.

I am not exactly sure for what reason cabal tries to build ghc on your system.

@Mikolaj do you have any input on this? Do you know if there are any related Cabal issues?

[Mikolaj]

Yes, there are:

haskell/cabal#8554
haskell/cabal#8489

It's cabal's fault if your package (or any of its deps [edit; rather, including deps]) depends on both ghc and Cabal >= 3.8. Will be fixed in cabal 3.10. For now --allow-newer, etc., should help.

[ysangkok]

@Mikolaj Are allow-newers also intended to work when upgrading boot packages?

For example, cabal build hspec-core --constraint='transformers>=0.6' yields the error

[__5] next goal: ghc (dependency of hspec-core)
[__5] rejecting: ghc-9.4.3/installed-9.4.3 (conflict: transformers==0.6.0.4,
ghc => transformers==0.5.6.2/installed-0.5.6.2)

So far, so good, that is expected.

But if I add --allow-newer=transformers,ghci,ghc-boot to get around this error, it still fails with the same error message. This is unexpected, as I thought I was telling it to ignore any bounds on dependencies for transformers.

This is with cabal-install version 3.8.1.0.

[Mikolaj]

It complains about ghc, but you say ghc-boot. These are different packages, I presume?

[ysangkok]

@Mikolaj even adding ghc and ghc-heap gives

 % cabal build hspec-core --constraint='transformers>=0.6' --allow-newer=transformers,ghci,ghc-boot,ghc,ghc-heap 
Resolving dependencies...
Error: cabal: Could not resolve dependencies:
[__0] trying: hspec-2.10.6 (user goal)
[__1] trying: base-4.17.0.0/installed-4.17.0.0 (dependency of hspec)
[__2] trying: QuickCheck-2.14.2 (dependency of hspec)
[__3] next goal: transformers (dependency of QuickCheck)
[__3] rejecting: transformers-0.5.6.2/installed-0.5.6.2 (constraint from
command line flag requires >=0.6)
[__3] trying: transformers-0.6.0.4
[__4] trying: hspec-core-2.10.6 (user goal)
[__5] next goal: ghc (dependency of hspec-core)
[__5] rejecting: ghc-9.4.3/installed-9.4.3 (conflict: transformers==0.6.0.4,
ghc => transformers==0.5.6.2/installed-0.5.6.2)
[__5] trying: ghc-9.4.2
[__6] next goal: ghci (dependency of ghc)
[__6] rejecting: ghci-9.4.3/installed-9.4.3 (conflict: transformers==0.6.0.4,
ghci => transformers==0.5.6.2/installed-0.5.6.2)
[__6] rejecting: ghci-8.10.2 (conflict: ghc => ghci>=9.4.2)
[__6] skipping: ghci-8.10.1, ghci-8.8.3, ghci-8.8.1, ghci-8.6.5, ghci-8.6.4,
ghci-8.6.1, ghci-8.4.4, ghci-8.4.3, ghci-8.4.2, ghci-8.4.1, ghci-8.2.2,
ghci-8.2.1, ghci-8.0.2, ghci-8.0.1 (has the same characteristics that caused
the previous version to fail: excluded by constraint '>=9.4.2' from 'ghc')
[__6] fail (backjumping, conflict set: ghc, ghci, transformers)
After searching the rest of the dependency tree exhaustively, these were the
goals I've had most trouble fulfilling: hspec-core, ghc, ghci, base,
transformers, hspec, QuickCheck
Try running with --minimize-conflict-set to improve the error message.

It's this line I don't understand

[__6] rejecting: ghci-9.4.3/installed-9.4.3 (conflict: transformers==0.6.0.4,
ghci => transformers==0.5.6.2/installed-0.5.6.2)

Why is there a conflict if newer transformers are allowed?

[sol]

#755 / hspec-2.10.7 addresses this.