Tune cast of config keys on read/CLI set

ixmp/_config.py

@@ -4,7 +4,7 @@
 from copy import copy
 from dataclasses import asdict, dataclass, field, fields, make_dataclass
 from pathlib import Path
-from typing import Any, Dict, Optional, Tuple, Type, Union
+from typing import Any, Dict, Optional, Tuple, Type
 
 log = logging.getLogger(__name__)
 
@@ -74,9 +74,7 @@ def _platform_default():
 class BaseValues:
     """Base class for storing configuration values."""
 
-    platform: Dict[str, Union[str, Dict[str, Any]]] = field(
-        default_factory=_platform_default
-    )
+    platform: dict = field(default_factory=_platform_default)
 
     def __getitem__(self, name):
         return getattr(self, name.replace(" ", "_"))
@@ -127,17 +125,16 @@ def keys(self) -> Tuple[str, ...]:
         return tuple(map(lambda f: f.name.replace("_", " "), fields(self)))
 
     def set(self, name: str, value: Any, strict: bool = True):
+        f = self.get_field(name)
+        if strict and f is None:
+            raise KeyError(name)
+
         # Retrieve the type for `name`; or None if unregistered
-        f = self.get_field(name) or None
         type_ = getattr(f, "type", None)
 
         try:
             # Attempt to cast to the correct type, if any
-            if type_ and strict:
-                value = type_(value)
-        except TypeError:
-            # `strict` but `name` is not registered; tried to call None(value)
-            raise KeyError(name)
+            value = type_(value) if type_ else value
         except Exception:
             raise TypeError(
                 f"expected {type_} for {repr(name)}; got {repr(value)} ({type(value)})"
@@ -244,13 +241,18 @@ def read(self):
             contents = config_path.read_text()
 
         try:
-            # Parse JSON and set values; _strict=False tolerates unregistered values
-            for key, value in json.loads(contents).items():
-                self.set(key, value, _strict=False)
+            data = json.loads(contents)
         except json.JSONDecodeError:
             print(config_path, contents)
             raise
 
+        # Parse JSON and set values
+        for key, value in data.items():
+            try:
+                self.set(key, value, _strict=True)  # Cast type for registered keys
+            except KeyError:
+                self.set(key, value, _strict=False)  # Tolerate unregistered keys
+
     # Public methods
 
     def get(self, name: str) -> Any: