Merge pull request 'don't keep appending --impure to nix_options when running tests' (#4128) from speed-up-flake-select into main

Reviewed-on: https://git.clan.lol/clan/clan-core/pulls/4128

pkgs/clan-cli/clan_cli/tests/fixtures_flakes.py

@@ -14,6 +14,7 @@ from clan_cli.tests import age_keys
 from clan_cli.tests.fixture_error import FixtureError
 from clan_cli.tests.root import CLAN_CORE
 from clan_cli.tests.temporary_dir import TEMPDIR
+from clan_lib import cmd
 from clan_lib.dirs import (
     TemplateType,
     clan_templates,
@@ -23,7 +24,7 @@ from clan_lib.dirs import (
 from clan_lib.flake import Flake
 from clan_lib.locked_open import locked_open
 from clan_lib.machines.machines import Machine
-from clan_lib.nix import nix_test_store
+from clan_lib.nix import nix_command, nix_test_store
 
 log = logging.getLogger(__name__)
 
@@ -86,6 +87,11 @@ def substitute(
     print(f"flake: {flake}")
     file.write_text(buf)
 
+    # Lock the flake after substitution if clan_core was replaced
+    if clan_core_flake:
+        flake_dir = file.parent
+        cmd.run(nix_command(["flake", "lock"]), cmd.RunOpts(cwd=flake_dir))
+
 
 class FlakeForTest(NamedTuple):
     path: Path