api/machines: use get_value_by_path utility for nested dict access

pkgs/clan-cli/clan_lib/machines/actions.py

@@ -9,6 +9,7 @@ from clan_lib.nix_models.clan import (
 )
 from clan_lib.persist.inventory_store import InventoryStore
 from clan_lib.persist.util import (
+    get_value_by_path,
     is_writeable_key,
     retrieve_typed_field_names,
     set_value_by_path,
@@ -132,10 +133,8 @@ def get_machine_fields_schema(machine: Machine) -> dict[str, FieldSchema]:
     # TODO: handle this more generically. I.e via json schema
     persisted_data = inventory_store._get_persisted()  # noqa: SLF001
     inventory = inventory_store.read()  #
-    all_tags = inventory.get("machines", {}).get(machine.name, {}).get("tags", [])
-    persisted_tags = (
-        persisted_data.get("machines", {}).get(machine.name, {}).get("tags", [])
-    )
+    all_tags = get_value_by_path(inventory, f"machines.{machine.name}.tags", [])
+    persisted_tags = get_value_by_path(persisted_data, f"machines.{machine.name}.tags", [])
     nix_tags = list_difference(all_tags, persisted_tags)
 
     return {

pkgs/clan-cli/clan_lib/persist/util.py

@@ -441,6 +441,27 @@ def delete_by_path(d: dict[str, Any], path: str) -> Any:
 type DictLike = dict[str, Any] | Any
 
 
+def get_value_by_path(d: DictLike, path: str, fallback: Any = None) -> Any:
+    """
+    Get the value at a specific dot-separated path in a nested dictionary.
+
+    If the path does not exist, it returns fallback.
+
+    :param d: The dictionary to get from.
+    :param path: The dot-separated path to the key (e.g., 'foo.bar').
+    """
+    keys = path.split(".")
+    current = d
+    for key in keys[:-1]:
+        current = current.setdefault(key, {})
+
+    if isinstance(current, dict):
+        return current.get(keys[-1], fallback)
+
+    return fallback
+
+
+
 def set_value_by_path(d: DictLike, path: str, content: Any) -> None:
     """
     Update the value at a specific dot-separated path in a nested dictionary.