haskell.packages.*.Cabal-syntax: expose dummy packages for GHC < 9.4

Before Cabal >= 3.8, Cabal-syntax did not exist, but there is a dummy
package Cabal-syntax-3.6.0.0 which can be used to prevent the constraint
solver from picking mutually incompatible versions of Cabal and
Cabal-syntax. Since we are now solving flags with Cabal >= 3.8, many
packages have a dependency on Cabal-syntax they did not have before,
requiring us to have a matching attribute in every package set. Using
the dummy package is the safest solution, although it is not required in
every case.

Fixes eval of jailbreak-cabal for GHC < 9.4.

1 files changed, 3 insertions, 0 deletions

diff --git a/pkgs/development/haskell-modules/configuration-ghc-9.0.x.nix b/pkgs/development/haskell-modules/configuration-ghc-9.0.x.nix
index 3c59f6b80d66..f32d12869b70 100644
--- a/pkgs/development/haskell-modules/configuration-ghc-9.0.x.nix
+++ b/pkgs/development/haskell-modules/configuration-ghc-9.0.x.nix
@@ -49,6 +49,9 @@ self: super: {
   # still the case when updating: https://gitlab.haskell.org/ghc/ghc/-/blob/0198841877f6f04269d6050892b98b5c3807ce4c/ghc.mk#L463
   xhtml = if self.ghc.hasHaddock or true then null else self.xhtml_3000_2_2_1;
 
+  # Need the Cabal-syntax-3.6.0.0 fake package for Cabal < 3.8 to allow callPackage and the constraint solver to work
+  Cabal-syntax = self.Cabal-syntax_3_6_0_0;
+
   # Jailbreaks & Version Updates
 
   # This `doJailbreak` can be removed once the following PR is released to Hackage: