fix: nix build

- update `gomod2nix.toml`
- add formatters as `nativeBuildInputs` for nix build
- export a `XDG_CACHE_HOME` for checks

Signed-off-by: Brian McGee <brian@bmcgee.ie>

gomod2nix.toml

@@ -46,6 +46,9 @@ schema = 3
   [mod."github.com/muesli/termenv"]
     version = "v0.15.2"
     hash = "sha256-Eum/SpyytcNIchANPkG4bYGBgcezLgej7j/+6IhqoMU="
+  [mod."github.com/otiai10/copy"]
+    version = "v1.14.0"
+    hash = "sha256-xsaL1ddkPS544y0Jv7u/INUALBYmYq29ddWvysLXk4A="
   [mod."github.com/pmezard/go-difflib"]
     version = "v1.0.0"
     hash = "sha256-/FtmHnaGjdvEIKAJtrUfEhV7EVo5A/eYrtdnUkuxLDA="
@@ -61,9 +64,6 @@ schema = 3
   [mod."github.com/vmihailenco/tagparser/v2"]
     version = "v2.0.0"
     hash = "sha256-M9QyaKhSmmYwsJk7gkjtqu9PuiqZHSmTkous8VWkWY0="
-  [mod."github.com/ztrue/shutdown"]
-    version = "v0.1.1"
-    hash = "sha256-+ygx5THHu9g+vBAn6b63tV35bvQGdRyto4pLhkontJI="
   [mod."go.etcd.io/bbolt"]
     version = "v1.3.8"
     hash = "sha256-ekKy8198B2GfPldHLYZnvNjID6x07dUPYKgFx84TgVs="

nix/devshell.nix

@@ -20,27 +20,15 @@
         }
       ];
 
-      packages = with pkgs; [
-        # golang
-        go
-        gotools
-        delve
-        golangci-lint
-
-        # formatters for testing
-        alejandra
-        elmPackages.elm-format
-        haskellPackages.cabal-fmt
-        haskellPackages.ormolu
-        mdsh
-        nodePackages.prettier
-        python3.pkgs.black
-        rufo
-        rustfmt
-        shellcheck
-        shfmt
-        terraform
-      ];
+      packages = with pkgs;
+        [
+          # golang
+          go
+          delve
+        ]
+        ++
+        # include formatters for development and testing
+        (import ./formatters.nix pkgs);
 
       commands = [
         {

nix/formatters.nix

@@ -0,0 +1,16 @@
+pkgs:
+with pkgs; [
+  alejandra
+  elmPackages.elm-format
+  gotools
+  haskellPackages.cabal-fmt
+  haskellPackages.ormolu
+  mdsh
+  nodePackages.prettier
+  python3.pkgs.black
+  rufo
+  rustfmt
+  shellcheck
+  shfmt
+  terraform
+]

nix/packages.nix

@@ -26,6 +26,14 @@
           "-X 'build.Version=${version}'"
         ];
 
+        # we need some formatters available for the tests
+        nativeBuildInputs = import ./formatters.nix pkgs;
+
+        preCheck = ''
+          XDG_CACHE_HOME=$(mktemp -d)
+          export XDG_CACHE_HOME
+        '';
+
         meta = with lib; {
           description = "treefmt: one CLI to format your repo";
           homepage = "https://git.numtide.com/numtide/treefmt";