bpo-38605: Make 'from __future__ import annotations' the default (GH-20434)

The hard part was making all the tests pass; there are some subtle issues here, because apparently the future import wasn't tested very thoroughly in previous Python versions.

For example, `inspect.signature()` returned type objects normally (except for forward references), but strings with the future import. We changed it to try and return type objects by calling `typing.get_type_hints()`, but fall back on returning strings if that function fails (which it may do if there are future references in the annotations that require passing in a specific namespace to resolve).

1 files changed, 2 insertions, 2 deletions

diff --git a/Lib/test/test_functools.py b/Lib/test/test_functools.py
index edd5773..bee9f91 100644
--- a/Lib/test/test_functools.py
+++ b/Lib/test/test_functools.py
@@ -618,7 +618,7 @@ class TestUpdateWrapper(unittest.TestCase):
 
 
     def _default_update(self):
-        def f(a:'This is a new annotation'):
+        def f(a: int):
             """This is a test"""
             pass
         f.attr = 'This is also a test'
@@ -635,7 +635,7 @@ class TestUpdateWrapper(unittest.TestCase):
         self.assertEqual(wrapper.__name__, 'f')
         self.assertEqual(wrapper.__qualname__, f.__qualname__)
         self.assertEqual(wrapper.attr, 'This is also a test')
-        self.assertEqual(wrapper.__annotations__['a'], 'This is a new annotation')
+        self.assertEqual(wrapper.__annotations__['a'], 'int')
         self.assertNotIn('b', wrapper.__annotations__)
 
     @unittest.skipIf(sys.flags.optimize >= 2,