Issue #11647: allow contextmanager objects to be used as decorators as described in the docs. Initial patch by Ysj Ray.

3 files changed, 33 insertions, 8 deletions

diff --git a/Lib/contextlib.py b/Lib/contextlib.py
index 4633cff..e90fc41 100644
--- a/Lib/contextlib.py
+++ b/Lib/contextlib.py
@@ -9,10 +9,23 @@ __all__ = ["contextmanager", "closing", "ContextDecorator"]
 
 class ContextDecorator(object):
     "A base class or mixin that enables context managers to work as decorators."
+
+    def _recreate_cm(self):
+        """Return a recreated instance of self.
+        
+        Allows otherwise one-shot context managers like
+        _GeneratorContextManager to support use as
+        decorators via implicit recreation.
+        
+        Note: this is a private interface just for _GCM in 3.2 but will be
+        renamed and documented for third party use in 3.3
+        """
+        return self
+
     def __call__(self, func):
         @wraps(func)
         def inner(*args, **kwds):
-            with self:
+            with self._recreate_cm():
                 return func(*args, **kwds)
         return inner
 
@@ -20,8 +33,15 @@ class ContextDecorator(object):
 class _GeneratorContextManager(ContextDecorator):
     """Helper for @contextmanager decorator."""
 
-    def __init__(self, gen):
-        self.gen = gen
+    def __init__(self, func, *args, **kwds):
+        self.gen = func(*args, **kwds)
+        self.func, self.args, self.kwds = func, args, kwds
+
+    def _recreate_cm(self):
+        # _GCM instances are one-shot context managers, so the
+        # CM must be recreated each time a decorated function is
+        # called
+        return self.__class__(self.func, *self.args, **self.kwds)
 
     def __enter__(self):
         try:
@@ -92,7 +112,7 @@ def contextmanager(func):
     """
     @wraps(func)
     def helper(*args, **kwds):
-        return _GeneratorContextManager(func(*args, **kwds))
+        return _GeneratorContextManager(func, *args, **kwds)
     return helper
 
 
diff --git a/Lib/test/test_contextlib.py b/Lib/test/test_contextlib.py
index d6bb5b8..6e38305 100644
--- a/Lib/test/test_contextlib.py
+++ b/Lib/test/test_contextlib.py
@@ -350,13 +350,13 @@ class TestContextDecorator(unittest.TestCase):
 
 
     def test_contextmanager_as_decorator(self):
-        state = []
         @contextmanager
         def woohoo(y):
             state.append(y)
             yield
             state.append(999)
 
+        state = []
         @woohoo(1)
         def test(x):
             self.assertEqual(state, [1])
@@ -364,6 +364,11 @@ class TestContextDecorator(unittest.TestCase):
         test('something')
         self.assertEqual(state, [1, 'something', 999])
 
+        # Issue #11647: Ensure the decorated function is 'reusable'
+        state = []
+        test('something else')
+        self.assertEqual(state, [1, 'something else', 999])
+
 
 # This is needed to make the test actually run under regrtest.py!
 def test_main():
diff --git a/Lib/test/test_with.py b/Lib/test/test_with.py
index a9d374b..e8cc8c0 100644
--- a/Lib/test/test_with.py
+++ b/Lib/test/test_with.py
@@ -14,8 +14,8 @@ from test.support import run_unittest
 
 
 class MockContextManager(_GeneratorContextManager):
-    def __init__(self, gen):
-        _GeneratorContextManager.__init__(self, gen)
+    def __init__(self, func, *args, **kwds):
+        super().__init__(func, *args, **kwds)
         self.enter_called = False
         self.exit_called = False
         self.exit_args = None
@@ -33,7 +33,7 @@ class MockContextManager(_GeneratorContextManager):
 
 def mock_contextmanager(func):
     def helper(*args, **kwds):
-        return MockContextManager(func(*args, **kwds))
+        return MockContextManager(func, *args, **kwds)
     return helper