Moved the environment assumption from ConfigLoader to _ProjectSettings

RELEASE.md

@@ -8,6 +8,7 @@
 * Added the functionality to choose a merging strategy for config files loaded with `OmegaConfigLoader`.
 * Modified the mechanism of importing datasets, raise more explicit error when dependencies are missing.
 * Added validation for configuration file used to override run commands via the CLI.
+* Moved the default environment `base` and `local` from config loader to `_ProjectSettings`. This enable the use of config loader as a standalone class without affecting existing Kedro Project users.
 
 ## Bug fixes and other changes
 * Added a new field `add-ons` to `pyproject.toml` when a project is created.

kedro/config/omegaconf_config.py

@@ -80,8 +80,8 @@ def __init__(  # noqa: PLR0913
         runtime_params: dict[str, Any] = None,
         *,
         config_patterns: dict[str, list[str]] = None,
-        base_env: str = "base",
-        default_run_env: str = "local",
+        base_env: str = None,
+        default_run_env: str = None,
         custom_resolvers: dict[str, Callable] = None,
         merge_strategy: dict[str, str] = None,
     ):
@@ -102,8 +102,8 @@ def __init__(  # noqa: PLR0913
             custom_resolvers: A dictionary of custom resolvers to be registered. For more information,
              see here: https://omegaconf.readthedocs.io/en/2.3_branch/custom_resolvers.html#custom-resolvers
         """
-        self.base_env = base_env
-        self.default_run_env = default_run_env
+        self.base_env = base_env or ""
+        self.default_run_env = default_run_env or ""
         self.merge_strategy = merge_strategy or {}
 
         self.config_patterns = {

kedro/framework/project/__init__.py

@@ -105,7 +105,9 @@ class _ProjectSettings(LazySettings):
         "CONFIG_LOADER_CLASS",
         default=_get_default_class("kedro.config.OmegaConfigLoader"),
     )
-    _CONFIG_LOADER_ARGS = Validator("CONFIG_LOADER_ARGS", default={})
+    _CONFIG_LOADER_ARGS = Validator(
+        "CONFIG_LOADER_ARGS", default={"base_env": "base", "default_run_env": "local"}
+    )
     _DATA_CATALOG_CLASS = _IsSubclassValidator(
         "DATA_CATALOG_CLASS", default=_get_default_class("kedro.io.DataCatalog")
     )