[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.

.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

@@ -994,11 +994,11 @@
         "nixpkgs": "nixpkgs_8"
       },
       "locked": {
-        "lastModified": 1678780648,
-        "narHash": "sha256-+BggREMl3p2J1lSzqFKFo+NStpmIqODBGXtolfhu6w8=",
+        "lastModified": 1679645506,
+        "narHash": "sha256-6hGH98lt8Q/0eEwNVBVJrOu4/hDstMXFDOM04GJy40M=",
         "owner": "serokell",
         "repo": "serokell.nix",
-        "rev": "d97df9f2783e284ddcc43203247e571ad11065f7",
+        "rev": "c4ac9aee348e2325e0a3abdee381e86820ec116b",
         "type": "github"
       },
       "original": {

flake.nix

@@ -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 ./.;
         };
       });
 }