test(inventory/instances): add tests for per machine resolution

lib/distributed-service/tests/per_machine_args.nix

@@ -0,0 +1,107 @@
+{ lib, 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";
+    };
+    # Define two roles with unmergeable interfaces
+    # Both define some 'timeout' but with completely different types.
+    roles.peer.interface =
+      { lib, ... }:
+      {
+        options.timeout = lib.mkOption {
+          type = lib.types.str;
+        };
+      };
+    roles.server.interface =
+      { lib, ... }:
+      {
+        options.timeout = lib.mkOption {
+          type = lib.types.submodule;
+        };
+      };
+
+    perMachine =
+      { instances, ... }:
+      {
+        nixosModule = instances;
+      };
+  };
+  machines = {
+    jon = { };
+    sara = { };
+  };
+  res = callInventoryAdapter {
+    inherit modules machines;
+    instances."instance_foo" = {
+      module = {
+        name = "A";
+      };
+      roles.peer.machines.jon = {
+        settings.timeout = lib.mkForce "foo-peer-jon";
+      };
+      roles.peer = {
+        settings.timeout = "foo-peer";
+      };
+    };
+    instances."instance_bar" = {
+      module = {
+        name = "A";
+      };
+      roles.peer.machines.jon = {
+        settings.timeout = "bar-peer-jon";
+      };
+    };
+    instances."instance_zaza" = {
+      module = {
+        name = "B";
+      };
+      roles.peer.tags.all = { };
+    };
+  };
+
+  filterInternals = lib.filterAttrs (n: _v: !lib.hasPrefix "_" n);
+in
+
+{
+
+  # settings should evaluate
+  test_per_machine_receives_instance_settings = {
+    expr = {
+      hasMachineSettings =
+        res.evals.self-A.config.result.allMachines.jon.nixosModule.instance_foo.roles.peer.machines.jon
+        ? settings;
+
+      # settings are specific.
+      # Below we access:
+      # instance = instance_foo
+      # roles = peer
+      # machines = jon
+      specificMachineSettings = filterInternals res.evals.self-A.config.result.allMachines.jon.nixosModule.instance_foo.roles.peer.machines.jon.settings;
+
+      hasRoleSettings =
+        res.evals.self-A.config.result.allMachines.jon.nixosModule.instance_foo.roles.peer ? settings;
+
+      # settings are specific.
+      # Below we access:
+      # instance = instance_foo
+      # roles = peer
+      # machines = *
+      specificRoleSettings = filterInternals res.evals.self-A.config.result.allMachines.jon.nixosModule.instance_foo.roles.peer.settings;
+    };
+    expected = {
+      hasMachineSettings = true;
+      specificMachineSettings = {
+        timeout = "foo-peer-jon";
+      };
+      hasRoleSettings = true;
+      specificRoleSettings = {
+        timeout = "foo-peer";
+      };
+    };
+  };
+}