Issue #8814: function annotations (the `__annotations__` attribute)

are now included in the set of attributes copied by default by
functools.wraps and functools.update_wrapper.  Patch by Terrence Cole.

2 files changed, 9 insertions, 4 deletions

diff --git a/Lib/functools.py b/Lib/functools.py
index 863706d..e244070 100644
--- a/Lib/functools.py
+++ b/Lib/functools.py
@@ -19,7 +19,7 @@ from operator import itemgetter
 # update_wrapper() and wraps() are tools to help write
 # wrapper functions that can handle naive introspection
 
-WRAPPER_ASSIGNMENTS = ('__module__', '__name__', '__doc__')
+WRAPPER_ASSIGNMENTS = ('__module__', '__name__', '__doc__', '__annotations__')
 WRAPPER_UPDATES = ('__dict__',)
 def update_wrapper(wrapper,
                    wrapped,
@@ -37,7 +37,8 @@ def update_wrapper(wrapper,
        function (defaults to functools.WRAPPER_UPDATES)
     """
     for attr in assigned:
-        setattr(wrapper, attr, getattr(wrapped, attr))
+        if hasattr(wrapped, attr):
+            setattr(wrapper, attr, getattr(wrapped, attr))
     for attr in updated:
         getattr(wrapper, attr).update(getattr(wrapped, attr, {}))
     # Return the wrapper so this can be used as a decorator via partial()
diff --git a/Lib/test/test_functools.py b/Lib/test/test_functools.py
index a02d37c..70a8ad6 100644
--- a/Lib/test/test_functools.py
+++ b/Lib/test/test_functools.py
@@ -182,11 +182,11 @@ class TestUpdateWrapper(unittest.TestCase):
                 self.assertTrue(wrapped_attr[key] is wrapper_attr[key])
 
     def _default_update(self):
-        def f():
+        def f(a:'This is a new annotation'):
             """This is a test"""
             pass
         f.attr = 'This is also a test'
-        def wrapper():
+        def wrapper(b:'This is the prior annotation'):
             pass
         functools.update_wrapper(wrapper, f)
         return wrapper, f
@@ -196,6 +196,8 @@ class TestUpdateWrapper(unittest.TestCase):
         self.check_wrapper(wrapper, f)
         self.assertEqual(wrapper.__name__, 'f')
         self.assertEqual(wrapper.attr, 'This is also a test')
+        self.assertEqual(wrapper.__annotations__['a'], 'This is a new annotation')
+        self.assertNotIn('b', wrapper.__annotations__)
 
     @unittest.skipIf(sys.flags.optimize >= 2,
                      "Docstrings are omitted with -O2 and above")
@@ -214,6 +216,7 @@ class TestUpdateWrapper(unittest.TestCase):
         self.check_wrapper(wrapper, f, (), ())
         self.assertEqual(wrapper.__name__, 'wrapper')
         self.assertEqual(wrapper.__doc__, None)
+        self.assertEqual(wrapper.__annotations__, {})
         self.assertFalse(hasattr(wrapper, 'attr'))
 
     def test_selective_update(self):
@@ -240,6 +243,7 @@ class TestUpdateWrapper(unittest.TestCase):
         functools.update_wrapper(wrapper, max)
         self.assertEqual(wrapper.__name__, 'max')
         self.assertTrue(wrapper.__doc__.startswith('max('))
+        self.assertEqual(wrapper.__annotations__, {})
 
 class TestWraps(TestUpdateWrapper):