Add dependent vars generator dynamic validation test

pkgs/clan-cli/tests/test_vars.py

@@ -919,3 +919,75 @@ def test_invalidation(
         str(machine.flake.path), machine.name, "my_generator/my_value"
     ).printable_value
     assert value2 == value2_new
+
+
+@pytest.mark.with_core
+def test_dynamic_invalidation(
+    monkeypatch: pytest.MonkeyPatch,
+    flake: ClanFlake,
+) -> None:
+    gen_prefix = "config.clan.core.vars.generators"
+
+    machine = Machine(name="my_machine", flake=Flake(str(flake.path)))
+
+    config = flake.machines[machine.name]
+    config["nixpkgs"]["hostPlatform"] = "x86_64-linux"
+
+    my_generator = config["clan"]["core"]["vars"]["generators"]["my_generator"]
+    my_generator["files"]["my_value"]["secret"] = False
+    my_generator["script"] = "echo -n $RANDOM > $out/my_value"
+
+    dependent_generator = config["clan"]["core"]["vars"]["generators"][
+        "dependent_generator"
+    ]
+    dependent_generator["files"]["my_value"]["secret"] = False
+    dependent_generator["dependencies"] = ["my_generator"]
+    dependent_generator["script"] = "echo -n $RANDOM > $out/my_value"
+
+    flake.refresh()
+
+    # this is an abuse
+    custom_nix = flake.path / "machines" / machine.name / "hardware-configuration.nix"
+    custom_nix.write_text("""
+        { config, ... }: let
+            p = config.clan.core.vars.generators.my_generator.files.my_value.path;
+        in {
+            clan.core.vars.generators.dependent_generator.validation = if builtins.pathExists p then builtins.readFile p else null;
+        }
+    """)
+
+    flake.refresh()
+    machine.flush_caches()
+    monkeypatch.chdir(flake.path)
+
+    # before generating, dependent generator validation should be empty; see bogus hardware-configuration.nix above
+    # we have to avoid `*.files.value` in this initial select because the generators haven't been run yet
+    generators_0 = machine.eval_nix(f"{gen_prefix}.*.{{validationHash}}")
+    assert generators_0["dependent_generator"]["validationHash"] is None
+
+    # generate both my_generator and (the dependent) dependent_generator
+    cli.run(["vars", "generate", "--flake", str(flake.path), machine.name])
+    machine.flush_caches()
+
+    # after generating once, dependent generator validation should be set
+    generators_1 = machine.eval_nix(gen_prefix)
+    assert generators_1["dependent_generator"]["validationHash"] is not None
+
+    # after generating once, neither generator should want to run again because `clan vars generate` should have re-evaluated the dependent generator's validationHash after executing the parent generator but before executing the dependent generator
+    # this ensures that validation can depend on parent generators while still only requiring a single pass
+    cli.run(["vars", "generate", "--flake", str(flake.path), machine.name])
+    machine.flush_caches()
+
+    generators_2 = machine.eval_nix(gen_prefix)
+    assert (
+        generators_1["dependent_generator"]["validationHash"]
+        == generators_2["dependent_generator"]["validationHash"]
+    )
+    assert (
+        generators_1["my_generator"]["files"]["my_value"]["value"]
+        == generators_2["my_generator"]["files"]["my_value"]["value"]
+    )
+    assert (
+        generators_1["dependent_generator"]["files"]["my_value"]["value"]
+        == generators_2["dependent_generator"]["files"]["my_value"]["value"]
+    )