feat(inventory/instances): prevent modules without explizit class from beeing used

lib/inventory/distributed-service/tests/default.nix

@@ -22,6 +22,15 @@ let
     }).config;
 
   flakeInputsFixture = {
+    # Example upstream module
+    upstream.clan.modules = {
+      uzzi = {
+        _class = "clan.service";
+        manifest = {
+          name = "uzzi-from-upstream";
+        };
+      };
+    };
   };
 
   callInventoryAdapter =
@@ -32,6 +41,7 @@ let
     };
 in
 {
+  resolve_module_spec = import ./import_module_spec.nix { inherit lib callInventoryAdapter; };
   test_simple =
     let
       res = callInventoryAdapter {

lib/inventory/distributed-service/tests/import_module_spec.nix

@@ -0,0 +1,65 @@
+{ callInventoryAdapter }:
+let
+  # Authored module
+  # A minimal module looks like this
+  # It isn't exactly doing anything but it's a valid module that produces an output
+  modules."A" = {
+    _class = "clan.service";
+    manifest = {
+      name = "network";
+    };
+  };
+
+  modules."B" =
+    { ... }:
+    {
+      options.stuff = "legacy-clan-service";
+    };
+
+  machines = {
+    jon = { };
+    sara = { };
+  };
+
+  resolve =
+    spec:
+    callInventoryAdapter {
+      inherit modules machines;
+      instances."instance_foo" = {
+        module = spec;
+      };
+    };
+in
+{
+  test_import_local_module_by_name = {
+    expr = (resolve { name = "A"; }).importedModuleWithInstances.instance_foo.resolvedModule;
+    expected = {
+      _class = "clan.service";
+      manifest = {
+        name = "network";
+      };
+    };
+  };
+  test_import_remote_module_by_name = {
+    expr =
+      (resolve {
+        name = "uzzi";
+        input = "upstream";
+      }).importedModuleWithInstances.instance_foo.resolvedModule;
+    expected = {
+      _class = "clan.service";
+      manifest = {
+        name = "uzzi-from-upstream";
+      };
+    };
+  };
+  # Currently this should fail
+  # TODO: Can we implement a default wrapper to make migration easy?
+  test_import_local_legacy_module = {
+    expr = (resolve { name = "B"; }).allMachines;
+    expectedError = {
+      type = "ThrownError";
+      msg = "Module 'B' is not a valid 'clan.service' module.*";
+    };
+  };
+}