Redone CVar storage as a dict of contextvars

asgiref/local.py

@@ -2,37 +2,38 @@
 import contextlib
 import contextvars
 import threading
-from typing import Any, Dict, Union
+from typing import Any, Union
 
 
 class _CVar:
     """Storage utility for Local."""
 
     def __init__(self) -> None:
-        self._data: "contextvars.ContextVar[Dict[str, Any]]" = contextvars.ContextVar(
-            "asgiref.local"
-        )
+        self._data: dict[str, contextvars.ContextVar[Any]] = {}
 
-    def __getattr__(self, key):
-        storage_object = self._data.get({})
+    def __getattr__(self, key: str) -> Any:
         try:
-            return storage_object[key]
+            var = self._data[key]
         except KeyError:
             raise AttributeError(f"{self!r} object has no attribute {key!r}")
 
+        try:
+            return var.get()
+        except LookupError:
+            raise AttributeError(f"{self!r} object has no attribute {key!r}")
+
     def __setattr__(self, key: str, value: Any) -> None:
         if key == "_data":
             return super().__setattr__(key, value)
 
-        storage_object = self._data.get({})
-        storage_object[key] = value
-        self._data.set(storage_object)
+        var = self._data.get(key)
+        if var is None:
+            self._data[key] = var = contextvars.ContextVar(key)
+        var.set(value)
 
     def __delattr__(self, key: str) -> None:
-        storage_object = self._data.get({})
-        if key in storage_object:
-            del storage_object[key]
-            self._data.set(storage_object)
+        if key in self._data:
+            del self._data[key]
         else:
             raise AttributeError(f"{self!r} object has no attribute {key!r}")