Fixed #3, use immutables

Author: fantix

contextvars/__init__.py

@@ -1,43 +1,15 @@
 import collections.abc
 import threading
 
+from immutables import Map
+
 
 __all__ = ('ContextVar', 'Context', 'Token', 'copy_context')
 
 
 _NO_DEFAULT = object()
 
 
-class _ContextData:
-
-    def __init__(self):
-        self._mapping = dict()
-
-    def __getitem__(self, key):
-        return self._mapping[key]
-
-    def __contains__(self, key):
-        return key in self._mapping
-
-    def __len__(self):
-        return len(self._mapping)
-
-    def __iter__(self):
-        return iter(self._mapping)
-
-    def set(self, key, value):
-        copy = _ContextData()
-        copy._mapping = self._mapping.copy()
-        copy._mapping[key] = value
-        return copy
-
-    def delete(self, key):
-        copy = _ContextData()
-        copy._mapping = self._mapping.copy()
-        del copy._mapping[key]
-        return copy
-
-
 class ContextMeta(type(collections.abc.Mapping)):
 
     # contextvars.Context is not subclassable.
@@ -52,7 +24,7 @@ def __new__(mcls, names, bases, dct):
 class Context(collections.abc.Mapping, metaclass=ContextMeta):
 
     def __init__(self):
-        self._data = _ContextData()
+        self._data = Map()
         self._prev_context = None
 
     def run(self, callable, *args, **kwargs):

setup.py

@@ -16,6 +16,9 @@
     author_email='[email protected]',
     packages=['contextvars'],
     provides=['contextvars'],
+    install_requires=[
+        'immutables==0.5',
+    ],
     license='Apache License, Version 2.0',
     classifiers=[
         'Development Status :: 3 - Alpha',