Fix 1210 and improves loading of inventory backends

kapitan/cli.py

@@ -21,7 +21,7 @@
 from kapitan import cached, defaults, setup_logging
 from kapitan.initialiser import initialise_skeleton
 from kapitan.inputs.jsonnet import jsonnet_file
-from kapitan.inventory import AVAILABLE_BACKENDS
+from kapitan.inventory import AVAILABLE_BACKENDS, InventoryBackends
 from kapitan.lint import start_lint
 from kapitan.refs.base import RefController, Revealer
 from kapitan.refs.cmd_parser import handle_refs_command
@@ -108,7 +108,7 @@ def build_parser():
     inventory_backend_parser.add_argument(
         "--inventory-backend",
         action="store",
-        default=from_dot_kapitan("inventory_backend", "inventory-backend", "reclass"),
+        default=from_dot_kapitan("inventory_backend", "inventory-backend", InventoryBackends.RECLASS),
         choices=AVAILABLE_BACKENDS.keys(),
         help="Select the inventory backend to use (default=reclass)",
     )

kapitan/inventory/__init__.py

@@ -1,14 +1,58 @@
+from .inventory import Inventory
+
+try:
+    from enum import StrEnum
+except ImportError:
+    from strenum import StrEnum
+
 from typing import Type
 
-from .inv_reclass import ReclassInventory
-from .inv_reclass_rs import ReclassRsInventory
-from .inv_omegaconf.inv_omegaconf import OmegaConfInventory
-from .inventory import Inventory
+
+class InventoryBackends(StrEnum):
+    """
+    Enumeration of available inventory backends.
+    """
+    RECLASS = "reclass"
+    RECLASS_RS = "reclass-rs"
+    OMEGACONF = "omegaconf"
+    DEFAULT = RECLASS
+
+
+def load_reclass_backend():
+    """
+    Enable the reclass inventory backend.
+    """
+    from .inv_reclass import ReclassInventory
+    return ReclassInventory
+
+
+def load_reclass_rs_backend():
+    """
+    Enable the reclass-rs inventory backend.
+    """
+    from .inv_reclass_rs import ReclassRsInventory
+    return ReclassRsInventory
+
+
+def load_omegaconf_backend():
+    """
+    Enable the omegaconf inventory backend.
+    """
+    from .inv_omegaconf.inv_omegaconf import OmegaConfInventory
+    return OmegaConfInventory
+
 
 # Dict mapping values for command line flag `--inventory-backend` to the
 # associated `Inventory` subclass.
 AVAILABLE_BACKENDS: dict[str, Type[Inventory]] = {
-    "reclass": ReclassInventory,
-    "reclass-rs": ReclassRsInventory,
-    "omegaconf": OmegaConfInventory,
+    InventoryBackends.RECLASS: load_reclass_backend,
+    InventoryBackends.RECLASS_RS: load_reclass_rs_backend,
+    InventoryBackends.OMEGACONF: load_omegaconf_backend,
 }
+
+
+def get_inventory_backend(backend_name: str) -> Type[Inventory]:
+    """
+    Get the `Inventory` subclass associated with the given `backend_name`.
+    """
+    return AVAILABLE_BACKENDS.get(backend_name, AVAILABLE_BACKENDS[InventoryBackends.DEFAULT])()

kapitan/resources.py

@@ -24,7 +24,7 @@
 from kapitan import __file__ as kapitan_install_path
 from kapitan.inputs.kadet import Dict
 from kapitan.errors import CompileError, InventoryError, KapitanError
-from kapitan.inventory import Inventory, ReclassInventory, AVAILABLE_BACKENDS
+from kapitan.inventory import Inventory, get_inventory_backend
 from kapitan.utils import PrettyDumper, deep_get, flatten_dict, render_jinja2_file, sha256_string
 
 logger = logging.getLogger(__name__)
@@ -327,10 +327,9 @@ def get_inventory(inventory_path, ignore_class_not_found: bool = False) -> Inven
     # select inventory backend
     backend_id = hasattr(cached.args, "inventory_backend") and cached.args.inventory_backend
     compose_target_name = hasattr(cached.args, "compose_target_name") and cached.args.compose_target_name
-    backend = AVAILABLE_BACKENDS.get(backend_id, AVAILABLE_BACKENDS.get("reclass"))
-    inventory_backend: Inventory = None
+    backend = get_inventory_backend(backend_id)
 
-    logger.debug(f"Using {backend_id} as inventory backend")
+    logger.debug(f"Using {backend.__name__} as inventory backend")
     inventory_backend = backend(inventory_path=inventory_path, compose_target_name=compose_target_name, ignore_class_not_found=ignore_class_not_found)
 
     cached.inv = inventory_backend
@@ -339,7 +338,7 @@ def get_inventory(inventory_path, ignore_class_not_found: bool = False) -> Inven
     # if we use forked processes, we need to load the inventory for kadet once 
     # and pass it to the children, to avoid re-reading the inventory for each child
     # TODO(adenaria): Improve to only do it for kadet
-    if cached.args.mp_method != "spawn":
+    if hasattr(cached.args, "mp_method") and cached.args.mp_method != "spawn":
         cached.inventory_global_kadet = Dict(cached.global_inv)
 
     # migrate inventory to selected inventory backend