Move checks to project.ncl

flake.nix

@@ -100,31 +100,6 @@
               program = pkgs.lib.getExe testScript;
             };
           };
-
-        checks.alejandra = pkgs.runCommand "check-alejandra" {} ''
-          ${pkgs.lib.getExe pkgs.alejandra} --check ${self}
-          touch $out
-        '';
-
-        checks.nickel-format =
-          pkgs.runCommand "check-nickel-format" {
-            buildInputs = [
-              inputs.nickel.packages.${system}.nickel-lang-cli
-            ];
-          } ''
-            cd ${self}
-            failed=""
-            for f in $(find . -name future -prune -or -name '*.ncl' -print); do
-              if ! diff -u "$f" <(nickel format -f "$f"); then
-                failed="$failed $f"
-              fi
-            done
-            if [ "$failed" != "" ]; then
-              echo "Following files need to be formatted: $failed"
-              exit 1
-            fi
-            touch $out
-          '';
       }
     );
 }

lib/builders.ncl

@@ -1,4 +1,4 @@
-let { NickelDerivation, Derivation, NixString, .. } = import "contracts.ncl" in
+let { NickelDerivation, Derivation, NixString, NixEnvironmentVariable, .. } = import "contracts.ncl" in
 
 let lib = import "lib.ncl" in
 
@@ -55,9 +55,9 @@ in
           args = ["-c", "set -euo pipefail; source .attrs.sh; source $stdenv/setup; genericBuild"],
         },
         structured_env = {},
-        env = {
-          stdenv = lib.import_nix "nixpkgs#stdenv"
-        },
+        env | { _ : NixEnvironmentVariable } = {
+            stdenv | default = lib.import_nix "nixpkgs#stdenv",
+          },
         nix_drv = env & structured_env,
       }
         | NickelPkg,

lib/contracts.ncl

@@ -303,6 +303,35 @@ from the Nix world) or a derivation defined in Nickel.
       output | String,
     },
 
+  NixEnvironmentVariable
+    | doc m%"
+        Covers all types that are allowed in Nix derivation's environment variables:
+        - strings
+        - arrays of strings
+        - records with string values
+      "%
+    = fun label value =>
+      let Contract =
+        if std.is_string value then
+          NixString
+        else if std.is_record value then
+          if std.record.has_field type_field value
+          || (
+            std.record.has_field "tag" value
+            && value.tag == 'SymbolicString
+            && std.record.has_field "prefix" value
+            && value.prefix == 'nix
+          ) then
+            NixString
+          else
+            { _ | NixString }
+        else if std.is_array value then
+          Array NixString
+        else
+          std.contract.blame_with_message "Must be string, array of strings or record with string values" label
+      in
+      std.contract.apply Contract label value,
+
   OrganistShells = {
     dev | NickelDerivation = build,
     build | NickelDerivation,

project.ncl

@@ -15,5 +15,45 @@ let import_nix = organist.lib.import_nix in
         nls = import_nix "nickel#lsp-nls",
       },
     },
+
+  flake.checks
+    | {
+      _ | {
+        version
+        = "",
+        env.stdenv
+        = import_nix "nixpkgs#stdenvNoCC",
+        ..
+      }
+    }
+    | { _ | organist.builders.NixpkgsPkg }
+    = {
+      alejandra = {
+        name = "check-alejandra",
+        env.buildCommand = nix-s%"
+          %{import_nix "nixpkgs#alejandra"}/bin/alejandra --check %{import_nix "self"}
+          touch $out
+        "%,
+      },
+
+      nickel-format = {
+        name = "check-nickel-format",
+        env.buildInputs.nickel = import_nix "nickel#nickel-lang-cli",
+        env.buildCommand = nix-s%"
+          cd %{import_nix "self"}
+          failed=""
+          for f in $(find . -name future -prune -or -name '*.ncl' -print); do
+            if ! diff -u "$f" <(nickel format -f "$f"); then
+              failed="$failed $f"
+            fi
+          done
+          if [ "$failed" != "" ]; then
+            echo "Following files need to be formatted: $failed"
+            exit 1
+          fi
+          touch $out
+        "%,
+      },
+    },
 }
   | organist.contracts.OrganistExpression