Switch to dhall-openapi project

The `dhall-openapi` subproject from the `dhall-haskell` repository
supersedes `dhall-kubernetes-generator`, so this change switches over
to using that project.

README.md

@@ -306,6 +306,41 @@ in
 
 ## Development
 
+### Updating the `dhall-openapi` dependency
+
+The `dhall-openapi` dependency is a subproject of the `dhall-haskell`
+repository, so in order to upgrade `dhall-openapi` you need to update the
+reference to the `dhall-haskell` repository.
+
+To upgrade to the latest version of the `dhall-openapi` package, run:
+
+```bash
+nix-prefetch-git --fetch-submodules https://github.com/dhall-lang/dhall-haskell.git > ./nix/dhall-haskell.json
+```
+
+If you want to build against a local copy of `dhall-haskell`, then edit the
+Nix code like this:
+
+```diff
+diff --git a/nix/nixpkgs.nix b/nix/nixpkgs.nix
+index 832ae1a..810e966 100644
+--- a/nix/nixpkgs.nix
++++ b/nix/nixpkgs.nix
+@@ -126,11 +126,7 @@ let
+                    json =
+                      builtins.fromJSON (builtins.readFile ./dhall-haskell.json);
+ 
+-                   dhall-haskell = pkgsNew.fetchFromGitHub {
+-                     owner = "dhall-lang";
+-                     repo = "dhall-haskell";
+-                     inherit (json) rev sha256 fetchSubmodules;
+-                   };
++                   dhall-haskell = ~/path/to/dhall-haskell;
+ 
+                  in
+                    (import "${dhall-haskell}/default.nix").dhall-openapi;
+```
+
 ### Adding a new Kubernetes releases
 
 To add a new supported release, run:

nix/dhall-haskell.json

@@ -0,0 +1,9 @@
+{
+  "url": "https://github.com/dhall-lang/dhall-haskell.git",
+  "rev": "05b12223f8d14055494d4c0cafc5db6807282c40",
+  "date": "2020-08-09T16:27:04+00:00",
+  "sha256": "0hgw2fq8n9v24pj3z6c28adwdmxffq5rxal12xk0vb7fvad46z42",
+  "fetchSubmodules": true,
+  "deepClone": false,
+  "leaveDotGit": false
+}

nix/nixpkgs.nix

@@ -13,7 +13,7 @@ let
 
           cd $out
 
-          ${pkgsNew.haskellPackages.dhall-kubernetes-generator}/bin/dhall-kubernetes-generator '${spec}'
+          ${pkgsNew.haskellPackages.dhall-openapi}/bin/openapi-to-dhall '${spec}'
         '';
 
     make-dhall-kubernetes-package =
@@ -120,28 +120,21 @@ let
            let
              previous = old.overrides or (_: _: {});
 
-             packages = pkgsNew.haskell.lib.packageSourceOverrides {
-               dhall-kubernetes-generator = ../dhall-kubernetes-generator;
-             };
+             extension = haskellPackagesNew: haskellPackagesOld: {
+               dhall-openapi =
+                 let
+                   json =
+                     builtins.fromJSON (builtins.readFile ./dhall-haskell.json);
 
-             packagesFromDirectory = pkgsNew.haskell.lib.packagesFromDirectory {
-               directory = ./haskell;
-             };
+                   dhall-haskell = ~/path/to/dhall-haskell;
 
-             manual = haskellPackagesNew: haskellPackagesOld: {
-               dhall =
-                 pkgsNew.haskell.lib.dontCheck haskellPackagesOld.dhall_1_33_0;
+                 in
+                   (import "${dhall-haskell}/default.nix").dhall-openapi;
 
-               dhall-json = haskellPackagesOld.dhall-json_1_7_0;
              };
 
            in
-             pkgsNew.lib.fold pkgsNew.lib.composeExtensions (_: _: {})
-               [ previous
-                 packages
-#                packagesFromDirectory
-                 manual
-               ];
+             pkgsNew.lib.composeExtensions (_: _: {}) extension;
       }
     );
   };

release.nix

@@ -5,8 +5,6 @@
 
 let
   products = {
-    inherit (pkgs.haskellPackages) dhall-kubernetes-generator;
-
     # Derivation that trivially depends on the input source code revision.
     # As this is included in the "dhall-lang" aggregate, it forces every
     # commit to have a corresponding GitHub status check, even if the