Make arguments passed to marshmallow explicit

Forwarding keyword arguments looks nice but makes the function typing
much weaker. Any typos in the keyword arguments taken by the function
end up undetected until they reach `marshmallow.Schema.load()` and then
they give an obscure error about some unexpected argument that was
never the intention to forward to `marshmallow`.

Signed-off-by: Leandro Lucarella <[email protected]>

Author: llucax

RELEASE_NOTES.md

@@ -26,7 +26,10 @@
         + The class is now immutable.
         + The constructor now accepts only keyword arguments.
 
-    * `load_config()`: the `base_schema` argument is now keyword-only.
+    * `load_config()`:
+
+         + The `base_schema` argument is now keyword-only.
+         + The arguments forwarded to `marshmallow.Schema.load()` now must be passed explicitly via the `marshmallow_load_kwargs` argument, as a `dict` to improve the type-checking.
 
 ## New Features
 

src/frequenz/sdk/config/_util.py

@@ -34,7 +34,7 @@ def load_config(
     /,
     *,
     base_schema: type[Schema] | None = None,
-    **marshmallow_load_kwargs: Any,
+    marshmallow_load_kwargs: dict[str, Any] | None = None,
 ) -> DataclassT:
     """Load a configuration from a dictionary into an instance of a configuration class.
 
@@ -63,13 +63,15 @@ def load_config(
         base_schema: An optional class to be used as a base schema for the configuration
             class. This allow using custom fields for example. Will be passed to
             [`marshmallow_dataclass.class_schema`][].
-        **marshmallow_load_kwargs: Additional arguments to be passed to
+        marshmallow_load_kwargs: Additional arguments to be passed to
             [`marshmallow.Schema.load`][].
 
     Returns:
         The loaded configuration as an instance of the configuration class.
     """
-    instance = class_schema(cls, base_schema)().load(config, **marshmallow_load_kwargs)
+    instance = class_schema(cls, base_schema)().load(
+        config, **(marshmallow_load_kwargs or {})
+    )
     # We need to cast because `.load()` comes from marshmallow and doesn't know which
     # type is returned.
     return cast(DataclassT, instance)

tests/config/test_util.py

@@ -100,7 +100,9 @@ def test_load_config_type_hints(mocker: MockerFixture) -> None:
     config: dict[str, Any] = {}
 
     # We add the type hint to test that the return type (hint) is correct
-    _: SimpleConfig = load_config(SimpleConfig, config, marshmallow_arg=1)
+    _: SimpleConfig = load_config(
+        SimpleConfig, config, marshmallow_load_kwargs={"marshmallow_arg": 1}
+    )
     mock_class_schema.return_value.load.assert_called_once_with(
         config, marshmallow_arg=1
     )