Merge pull request #30 from ncoghlan/issue-29-switch-to-calver-update-min-py-version

Issue #29: Switch to CalVer, require Python >= 3.6

.github/workflows/release.yml

@@ -18,7 +18,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v2
         with:
-          python-version: 3.8
+          python-version: 3.9
 
       - name: Get pip cache dir
         id: pip-cache

.github/workflows/test.yml

@@ -8,7 +8,7 @@ jobs:
     strategy:
       max-parallel: 5
       matrix:
-        python-version: [2.7, 3.5, 3.6, 3.7, 3.8, 'pypy2', 'pypy3']
+        python-version: [3.6, 3.7, 3.8, 3.9, '3.10.0-beta - 3.10', 'pypy3']
 
     steps:
     - uses: actions/checkout@v2

NEWS.rst

@@ -1,6 +1,33 @@
 Release History
 ---------------
 
+21.6.0 (2021-06-TBD)
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+* Switched to calendar based versioning rather than continuing with pre-1.0
+  semantic versioning (`#29 <https://github.com/jazzband/contextlib2/issues/29>`__)
+* Due to the inclusion of asynchronous features from Python 3.7+, the
+  minimum supported Python version is now Python 3.6
+  (`#29 <https://github.com/jazzband/contextlib2/issues/29>`__)
+* (WIP) Synchronised with the Python 3.10 version of contextlib, bringing the
+  following new features to Python 3.6+ (
+  `#12 <https://github.com/jazzband/contextlib2/issues/12>`__,
+  `#19 <https://github.com/jazzband/contextlib2/issues/19>`__,
+  `#27 <https://github.com/jazzband/contextlib2/issues/27>`__):
+
+  * ``asyncontextmanager`` (Python 3.7)
+  * ``aclosing`` (Python 3.10)
+  * ``AbstractAsyncContextManager`` (Python 3.7)
+  * ``AsyncContextDecorator`` (Python 3.10)
+  * ``AsyncExitStack`` (Python 3.7)
+  * async support in ``nullcontext`` (Python 3.10)
+
+* Updates to the default compatibility testing matrix:
+
+  * Added: CPython 3.9, CPython 3.10
+  * Dropped: CPython 2.7, CPython 3.5, PyPy2
+
+
 0.6.0.post1 (2019-10-10)
 ^^^^^^^^^^^^^^^^^^^^^^^^
 

VERSION.txt

@@ -1 +1 @@
-0.6.0.post1
+21.6.0

contextlib2.py

@@ -6,6 +6,8 @@ import warnings
 from collections import deque
 from functools import wraps
 
+from _collections_abc import _check_methods
+
 __all__ = ["contextmanager", "closing", "nullcontext",
            "AbstractContextManager",
            "ContextDecorator", "ExitStack",
@@ -14,43 +16,7 @@ __all__ = ["contextmanager", "closing", "nullcontext",
 # Backwards compatibility
 __all__ += ["ContextStack"]
 
-
+class AbstractContextManager(abc.ABC):
-# Backport abc.ABC
-if sys.version_info[:2] >= (3, 4):
-    _abc_ABC = abc.ABC
-else:
-    _abc_ABC = abc.ABCMeta('ABC', (object,), {'__slots__': ()})
-
-
-# Backport classic class MRO
-def _classic_mro(C, result):
-    if C in result:
-        return
-    result.append(C)
-    for B in C.__bases__:
-        _classic_mro(B, result)
-    return result
-
-
-# Backport _collections_abc._check_methods
-def _check_methods(C, *methods):
-    try:
-        mro = C.__mro__
-    except AttributeError:
-        mro = tuple(_classic_mro(C, []))
-
-    for method in methods:
-        for B in mro:
-            if method in B.__dict__:
-                if B.__dict__[method] is None:
-                    return NotImplemented
-                break
-        else:
-            return NotImplemented
-    return True
-
-
-class AbstractContextManager(_abc_ABC):
     """An abstract base class for context managers."""
 
     def __enter__(self):
@@ -167,7 +133,7 @@ class _GeneratorContextManager(ContextDecorator):
                 # Likewise, avoid suppressing if a StopIteration exception
                 # was passed to throw() and later wrapped into a RuntimeError
                 # (see PEP 479).
-                if _HAVE_EXCEPTION_CHAINING and exc.__cause__ is value:
+                if exc.__cause__ is value:
                     return False
                 raise
             except:
@@ -313,58 +279,32 @@ class suppress(object):
         return exctype is not None and issubclass(exctype, self._exceptions)
 
 
-# Context manipulation is Python 3 only
+# Context manipulation helpers
-_HAVE_EXCEPTION_CHAINING = sys.version_info[0] >= 3
+def _make_context_fixer(frame_exc):
-if _HAVE_EXCEPTION_CHAINING:
+    def _fix_exception_context(new_exc, old_exc):
-    def _make_context_fixer(frame_exc):
+        # Context may not be correct, so find the end of the chain
-        def _fix_exception_context(new_exc, old_exc):
+        while 1:
-            # Context may not be correct, so find the end of the chain
+            exc_context = new_exc.__context__
-            while 1:
+            if exc_context is old_exc:
-                exc_context = new_exc.__context__
+                # Context is already set correctly (see issue 20317)
-                if exc_context is old_exc:
+                return
-                    # Context is already set correctly (see issue 20317)
+            if exc_context is None or exc_context is frame_exc:
-                    return
+                break
-                if exc_context is None or exc_context is frame_exc:
+            new_exc = exc_context
-                    break
+        # Change the end of the chain to point to the exception
-                new_exc = exc_context
+        # we expect it to reference
-            # Change the end of the chain to point to the exception
+        new_exc.__context__ = old_exc
-            # we expect it to reference
+    return _fix_exception_context
-            new_exc.__context__ = old_exc
-        return _fix_exception_context
 
-    def _reraise_with_existing_context(exc_details):
+def _reraise_with_existing_context(exc_details):
-        try:
+    try:
-            # bare "raise exc_details[1]" replaces our carefully
+        # bare "raise exc_details[1]" replaces our carefully
-            # set-up context
+        # set-up context
-            fixed_ctx = exc_details[1].__context__
+        fixed_ctx = exc_details[1].__context__
-            raise exc_details[1]
+        raise exc_details[1]
-        except BaseException:
+    except BaseException:
-            exc_details[1].__context__ = fixed_ctx
+        exc_details[1].__context__ = fixed_ctx
-            raise
+        raise
-else:
-    # No exception context in Python 2
-    def _make_context_fixer(frame_exc):
-        return lambda new_exc, old_exc: None
-
-    # Use 3 argument raise in Python 2,
-    # but use exec to avoid SyntaxError in Python 3
-    def _reraise_with_existing_context(exc_details):
-        exc_type, exc_value, exc_tb = exc_details
-        exec("raise exc_type, exc_value, exc_tb")
-
-# Handle old-style classes if they exist
-try:
-    from types import InstanceType
-except ImportError:
-    # Python 3 doesn't have old-style classes
-    _get_type = type
-else:
-    # Need to handle old-style context managers on Python 2
-    def _get_type(obj):
-        obj_type = type(obj)
-        if obj_type is InstanceType:
-            return obj.__class__  # Old-style class
-        return obj_type  # New-style class
 
 
 # Inspired by discussions on http://bugs.python.org/issue13585
@@ -407,7 +347,7 @@ class ExitStack(object):
         """
         # We use an unbound method rather than a bound method to follow
         # the standard lookup behaviour for special methods
-        _cb_type = _get_type(exit)
+        _cb_type = type(exit)
         try:
             exit_method = _cb_type.__exit__
         except AttributeError:
@@ -437,7 +377,7 @@ class ExitStack(object):
         returns the result of the __enter__ method.
         """
         # We look up the special methods on the type to match the with statement
-        _cm_type = _get_type(cm)
+        _cm_type = type(cm)
         _exit = _cm_type.__exit__
         result = _cm_type.__enter__(cm)
         self._push_cm_exit(cm, _exit)

setup.py

@@ -7,7 +7,7 @@ except ImportError:
 setup(
     name='contextlib2',
     version=open('VERSION.txt').read().strip(),
-    python_requires='>=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*',
+    python_requires='>=3.6',
     py_modules=['contextlib2'],
     license='PSF License',
     description='Backports and enhancements for the contextlib module',
@@ -19,13 +19,13 @@ setup(
         'Development Status :: 5 - Production/Stable',
         'License :: OSI Approved :: Python Software Foundation License',
         # These are the Python versions tested, it may work on others
-        'Programming Language :: Python :: 2',
+        # It definitely won't work on versions without native async support
-        'Programming Language :: Python :: 2.7',
         'Programming Language :: Python :: 3',
-        'Programming Language :: Python :: 3.4',
-        'Programming Language :: Python :: 3.5',
         'Programming Language :: Python :: 3.6',
         'Programming Language :: Python :: 3.7',
+        'Programming Language :: Python :: 3.8',
+        'Programming Language :: Python :: 3.9',
+        'Programming Language :: Python :: 3.10',
     ],
 
 )

test_contextlib2.py

@@ -9,9 +9,6 @@ import __future__ # For PEP 479 conditional test
 import contextlib2
 from contextlib2 import *  # Tests __all__
 
-if not hasattr(unittest.TestCase, "assertRaisesRegex"):
-    import unittest2 as unittest
-
 requires_docstrings = unittest.skipIf(sys.flags.optimize >= 2,
                                       "Test requires docstrings")
 
@@ -421,9 +418,6 @@ class TestContextDecorator(unittest.TestCase):
         test('something else')
         self.assertEqual(state, [1, 'something else', 999])
 
-# Detailed exception chaining checks only make sense on Python 3
-check_exception_chaining = contextlib2._HAVE_EXCEPTION_CHAINING
-
 class TestExitStack(unittest.TestCase):
 
     @requires_docstrings
@@ -592,18 +586,16 @@ class TestExitStack(unittest.TestCase):
                         with RaiseExc(ValueError):
                             1 / 0
         except IndexError as exc:
-            if check_exception_chaining:
+            self.assertIsInstance(exc.__context__, KeyError)
-                self.assertIsInstance(exc.__context__, KeyError)
+            self.assertIsInstance(exc.__context__.__context__, AttributeError)
-                self.assertIsInstance(exc.__context__.__context__, AttributeError)
+            # Inner exceptions were suppressed
-                # Inner exceptions were suppressed
+            self.assertIsNone(exc.__context__.__context__.__context__)
-                self.assertIsNone(exc.__context__.__context__.__context__)
         else:
             self.fail("Expected IndexError, but no exception was raised")
         # Check the inner exceptions
         inner_exc = SuppressExc.saved_details[1]
         self.assertIsInstance(inner_exc, ValueError)
-        if check_exception_chaining:
+        self.assertIsInstance(inner_exc.__context__, ZeroDivisionError)
-            self.assertIsInstance(inner_exc.__context__, ZeroDivisionError)
 
     def test_exit_exception_chaining(self):
         # Ensure exception chaining matches the reference behaviour
@@ -624,18 +616,16 @@ class TestExitStack(unittest.TestCase):
                 stack.callback(raise_exc, ValueError)
                 1 / 0
         except IndexError as exc:
-            if check_exception_chaining:
+            self.assertIsInstance(exc.__context__, KeyError)
-                self.assertIsInstance(exc.__context__, KeyError)
+            self.assertIsInstance(exc.__context__.__context__, AttributeError)
-                self.assertIsInstance(exc.__context__.__context__, AttributeError)
+            # Inner exceptions were suppressed
-                # Inner exceptions were suppressed
+            self.assertIsNone(exc.__context__.__context__.__context__)
-                self.assertIsNone(exc.__context__.__context__.__context__)
         else:
             self.fail("Expected IndexError, but no exception was raised")
         # Check the inner exceptions
         inner_exc = saved_details[0][1]
         self.assertIsInstance(inner_exc, ValueError)
-        if check_exception_chaining:
+        self.assertIsInstance(inner_exc.__context__, ZeroDivisionError)
-            self.assertIsInstance(inner_exc.__context__, ZeroDivisionError)
 
     def test_exit_exception_non_suppressing(self):
         # http://bugs.python.org/issue19092
@@ -689,12 +679,11 @@ class TestExitStack(unittest.TestCase):
                 raise exc1
         except Exception as exc:
             self.assertIs(exc, exc4)
-            if check_exception_chaining:
+            self.assertIs(exc.__context__, exc3)
-                self.assertIs(exc.__context__, exc3)
+            self.assertIs(exc.__context__.__context__, exc2)
-                self.assertIs(exc.__context__.__context__, exc2)
+            self.assertIs(exc.__context__.__context__.__context__, exc1)
-                self.assertIs(exc.__context__.__context__.__context__, exc1)
+            self.assertIsNone(
-                self.assertIsNone(
+                    exc.__context__.__context__.__context__.__context__)
-                        exc.__context__.__context__.__context__.__context__)
 
     def test_exit_exception_with_existing_context(self):
         # Addresses a lack of test coverage discovered after checking in a
@@ -716,16 +705,13 @@ class TestExitStack(unittest.TestCase):
                 raise exc1
         except Exception as exc:
             self.assertIs(exc, exc5)
-            if check_exception_chaining:
+            self.assertIs(exc.__context__, exc4)
-                self.assertIs(exc.__context__, exc4)
+            self.assertIs(exc.__context__.__context__, exc3)
-                self.assertIs(exc.__context__.__context__, exc3)
+            self.assertIs(exc.__context__.__context__.__context__, exc2)
-                self.assertIs(exc.__context__.__context__.__context__, exc2)
+            self.assertIs(
-                self.assertIs(
+                exc.__context__.__context__.__context__.__context__, exc1)
-                    exc.__context__.__context__.__context__.__context__, exc1)
+            self.assertIsNone(
-                self.assertIsNone(
+                exc.__context__.__context__.__context__.__context__.__context__)
-                    exc.__context__.__context__.__context__.__context__.__context__)
-
-
 
     def test_body_exception_suppress(self):
         def suppress_exc(*exc_details):
@@ -824,10 +810,9 @@ class TestExitStack(unittest.TestCase):
         exc = err_ctx.exception
         self.assertIsInstance(exc, UniqueException)
         self.assertIsInstance(exc.__cause__, UniqueRuntimeError)
-        if check_exception_chaining:
+        self.assertIs(exc.__context__, exc.__cause__)
-            self.assertIs(exc.__context__, exc.__cause__)
+        self.assertIsNone(exc.__cause__.__context__)
-            self.assertIsNone(exc.__cause__.__context__)
+        self.assertIsNone(exc.__cause__.__cause__)
-            self.assertIsNone(exc.__cause__.__cause__)
 
 
 class TestRedirectStream:

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py{27,35,36,37,py,py3}
+envlist = py{36,37,38,39,3_10,py3}
 skip_missing_interpreters = True
 
 [testenv]
@@ -9,15 +9,12 @@ commands =
     coverage xml
 deps =
     coverage
-    py27: unittest2
-    pypy: unittest2
 
 [gh-actions]
 python =
-    2.7: py27
-    3.5: py35
     3.6: py36
     3.7: py37
     3.8: py38
-    pypy2: pypy
+    3.9: py39
+    3.10: py3_10
     pypy3: pypy3