[INT-159] Add hpack check (#20)

Problem: We want to be able to check if cabal file is up to date.

Solution: Add hpack check.

Author: Sereja313

.github/workflows/check.yml

@@ -30,6 +30,10 @@ jobs:
         run: nix build -L .#checks.x86_64-linux.trailing-whitespace
         if: success() || failure()
 
+      - name: check-hpack
+        run: nix build -L .#checks.x86_64-linux.hpack
+        if: success() || failure()
+
   # Export JSON serialized ghc-versions
   ghc-versions:
     runs-on: [self-hosted, nix]

flake.lock

@@ -92,6 +92,10 @@
         # nixpkgs revision pinned by this flake
         legacyPackages = pkgs;
 
+        devShells.default = pkgs.mkShell {
+            buildInputs = [ pkgs.hpack ];
+          };
+
         # used to dynamically build a matrix in the GitHub pipeline
         ghc-matrix = {
           include = map (ver: { ghc = ver; }) ghc-versions;
@@ -105,6 +109,8 @@
 
           hlint = pkgs.build.haskell.hlint ./.;
           stylish-haskell = pkgs.build.haskell.stylish-haskell ./.;
+
+          hpack = pkgs.build.haskell.hpack ./.;
         };
       });
 }