chore: better solution for handling store paths in variables

lib/impl/jobPatched.nix

@@ -11,21 +11,33 @@ in
     pipelineName,
     nixConfig,
   }:
-    job
+    (builtins.removeAttrs job ["variables" "cache"])
     // (optionalAttrs nixConfig.enable (
       (prependToBeforeScript ["source setup_nix_ci \"gitlab-ci:pipeline:${pipelineName}:job-deps:${key}\""] job)
       // (appendToAfterScript ["finalize_nix_ci"] job)
     ))
-    // optionalAttrs nixConfig.enable {
+    // optionalAttrs nixConfig.enable (
+      (let
         variables =
           (filterJobVariables false job)
           // optionalAttrs nixConfig.enableRunnerCache {
             NIX_CI_CACHE_STRATEGY = "runner";
           };
+      in
+        # filter empty variables
+        optionalAttrs (variables != {}) {
+          inherit variables;
+        })
+      // (let
         cache =
           (toList (job.cache or []))
           ++ (optional nixConfig.enableRunnerCache {
             key = nixConfig.runnerCacheKey;
             paths = [".nix-cache/"];
           });
-    }
+      in
+        # filter empty cache
+        optionalAttrs (cache != []) {
+          inherit cache;
+        })
+    )

tests/cilib_test.nix

@@ -148,10 +148,7 @@
         name = "handle store paths in variables";
         expected = {
           stages = ["test"];
-          test = {
+          test.stage = "test";
-            stage = "test";
-            variables."TEST" = "${pkgs.hello}";
-          };
         };
         actual =
           (mkPipeline {