chore: pull facade type improvements from juju#1104

juju/client/facade.py

@@ -14,7 +14,7 @@
 from collections import defaultdict
 from glob import glob
 from pathlib import Path
-from typing import Any, Mapping, Sequence
+from typing import Any, Mapping, Sequence, TypeVar, overload
 
 import packaging.version
 import typing_inspect
@@ -183,7 +183,7 @@ def ref_type(self, obj):
         return self.get_ref_type(obj["$ref"])
 
 
-CLASSES = {}
+CLASSES: dict[str, type[Type]] = {}
 factories = codegen.Capture()
 
 
@@ -479,37 +479,48 @@ def ReturnMapping(cls):  # noqa: N802
     def decorator(f):
         @functools.wraps(f)
         async def wrapper(*args, **kwargs):
-            nonlocal cls
             reply = await f(*args, **kwargs)
-            if cls is None:
-                return reply
-            if "error" in reply:
-                cls = CLASSES["Error"]
-            if typing_inspect.is_generic_type(cls) and issubclass(
-                typing_inspect.get_origin(cls), Sequence
-            ):
-                parameters = typing_inspect.get_parameters(cls)
-                result = []
-                item_cls = parameters[0]
-                for item in reply:
-                    result.append(item_cls.from_json(item))
-                    """
-                    if 'error' in item:
-                        cls = CLASSES['Error']
-                    else:
-                        cls = item_cls
-                    result.append(cls.from_json(item))
-                    """
-            else:
-                result = cls.from_json(reply["response"])
-
-            return result
+            return _convert_response(reply, cls=cls)
 
         return wrapper
 
     return decorator
 
 
+@overload
+def _convert_response(response: dict[str, Any], *, cls: type[SomeType]) -> SomeType: ...
+
+
+@overload
+def _convert_response(response: dict[str, Any], *, cls: None) -> dict[str, Any]: ...
+
+
+def _convert_response(response: dict[str, Any], *, cls: type[Type] | None) -> Any:
+    if cls is None:
+        return response
+    if "error" in response:
+        cls = CLASSES["Error"]
+    if typing_inspect.is_generic_type(cls) and issubclass(
+        typing_inspect.get_origin(cls), Sequence
+    ):
+        parameters = typing_inspect.get_parameters(cls)
+        result = []
+        item_cls = parameters[0]
+        for item in response:
+            result.append(item_cls.from_json(item))
+            """
+            if 'error' in item:
+                cls = CLASSES['Error']
+            else:
+                cls = item_cls
+            result.append(cls.from_json(item))
+            """
+    else:
+        result = cls.from_json(response["response"])
+
+    return result
+
+
 def make_func(cls, name, description, params, result, _async=True):
     indent = "    "
     args = Args(cls.schema, params)
@@ -663,7 +674,7 @@ async def rpc(self, msg: dict[str, _RichJson]) -> _Json:
         return result
 
     @classmethod
-    def from_json(cls, data):
+    def from_json(cls, data: Type | str | dict[str, Any] | list[Any]) -> Type | None:
         def _parse_nested_list_entry(expr, result_dict):
             if isinstance(expr, str):
                 if ">" in expr or ">=" in expr:
@@ -742,6 +753,9 @@ def get(self, key, default=None):
         return getattr(self, attr, default)
 
 
+SomeType = TypeVar("SomeType", bound=Type)
+
+
 class Schema(dict):
     def __init__(self, schema):
         self.name = schema["Name"]