pytest: add simple clan_flake function

Takes a clan nix expression as a string
Is empty by default and does nothing
Expensive lockfile patching is done once per session

pkgs/clan-cli/clan_lib/fixtures/flake_hooks.py

@@ -23,9 +23,17 @@ def substitute_flake_inputs(clan_dir: Path, clan_core_path: Path) -> None:
     assert flake_lock.exists(), "flake.lock should exist after flake update"
 
 
-@pytest.fixture
+@pytest.fixture()
 def offline_flake_hook(clan_core: Path) -> Callable[[Path], None]:
     def patch(clan_dir: Path) -> None:
         substitute_flake_inputs(clan_dir, clan_core)
 
     return patch
+
+
+@pytest.fixture(scope="session")
+def offline_session_flake_hook(clan_core: Path) -> Callable[[Path], None]:
+    def patch(clan_dir: Path) -> None:
+        substitute_flake_inputs(clan_dir, clan_core)
+
+    return patch

pkgs/clan-cli/clan_lib/fixtures/flakes/flakes.py

@@ -0,0 +1,65 @@
+import shutil
+from collections.abc import Callable, Iterator
+from contextlib import contextmanager
+from pathlib import Path
+from typing import Any
+
+import pytest
+from clan_lib.clan.create import CreateOptions, create_clan
+from clan_lib.flake.flake import Flake
+
+
+@pytest.fixture(scope="session")
+def offline_template(tmp_path_factory: Any, offline_session_flake_hook: Any) -> Path:
+    base_tmp = tmp_path_factory.mktemp("minimal-clan-template")
+    template = Path(__file__).parent / Path("lib_clan")
+    dst_dir = base_tmp / "offline"
+
+    shutil.copytree(template, dst_dir, dirs_exist_ok=True, symlinks=True)
+
+    # Emtpy clan.nix file for evaluation of the template
+    clan_file = dst_dir / "clan.nix"
+    with (clan_file).open("w") as f:
+        f.write(r"""{ }""")
+
+    # expensive call ~6 seconds
+    # Run in session scope to avoid repeated calls
+    offline_session_flake_hook(dst_dir)
+
+    return dst_dir
+
+
+@pytest.fixture()
+def patch_clan_template(monkeypatch: Any, offline_template: Path) -> None:
+    @contextmanager
+    def fake_clan_template(
+        flake: Flake,
+        template_ident: str,
+        dst_dir: Path,
+        post_process: Callable[[Path], None] | None = None,
+    ) -> Iterator[Path]:
+        # Just yield static destination directory without any processing
+        shutil.copytree(offline_template, dst_dir, dirs_exist_ok=True, symlinks=True)
+        yield dst_dir
+
+    monkeypatch.setattr("clan_lib.clan.create.clan_template", fake_clan_template)
+
+
+@pytest.fixture()
+def clan_flake(tmp_path: Path, patch_clan_template: Any) -> Callable[[str], Flake]:
+    def factory(clan_expr: str) -> Flake:
+        # TODO: Make more options configurable
+        dest = tmp_path / "my-clan"
+        opts = CreateOptions(
+            dest,
+            template="minimal",  # Has no effect, since we patch the clan_template
+            update_clan=False,  # Takes ~6 seconds, generate a static lockfile per session.
+        )
+        create_clan(opts)
+
+        with (dest / "clan.nix").open("w") as f:
+            f.write(clan_expr)
+
+        return Flake(str(dest))
+
+    return factory

pkgs/clan-cli/clan_lib/fixtures/flakes/lib_clan/flake.nix

@@ -0,0 +1,26 @@
+{
+  inputs.clan-core.url = "https://git.clan.lol/clan/clan-core/archive/main.tar.gz";
+  inputs.nixpkgs.follows = "clan-core/nixpkgs";
+
+  outputs =
+    { self, clan-core, ... }:
+    let
+      clan = clan-core.lib.clan ({
+        inherit self;
+        imports = [
+          ./clan.nix
+
+          (
+            { lib, ... }:
+            {
+              meta.name = lib.mkDefault "_somename_";
+            }
+          )
+        ];
+      });
+    in
+    {
+      clan = clan.config;
+      inherit (clan.config) nixosConfigurations nixosModules clanInternals;
+    };
+}