Update testing etc for Python 3.8

.github/workflows/ci.yml

@@ -37,6 +37,9 @@ jobs:
           - name: CPython 3.7
             tox: py37
             action: 3.7
+          - name: CPython 3.8
+            tox: py38
+            action: 3.8
         reactor:
           - name: default
             tox: default

.travis.yml

@@ -8,6 +8,9 @@ matrix:
     - python: 3.7
       dist: xenial
       sudo: true
+    - python: 3.8
+      dist: xenial
+      sudo: true
 
 addons:
   apt:

README.rst

@@ -18,6 +18,59 @@ which uses the twisted framework. test functions can return Deferred
 objects and pytest will wait for their completion with this plugin.
 
 
+NOTICE: Python 3.8 with asyncio support
+=======================================
+
+In Python 3.8, asyncio changed the default loop implementation to use
+their proactor.  The proactor does not implement some methods used by
+Twisted's asyncio support.  The result is a ``NotImplementedError``
+exception such as below.
+
+.. code-block:: pytb
+
+    <snip>
+      File "c:\projects\pytest-twisted\.tox\py38-asyncioreactor\lib\site-packages\twisted\internet\asyncioreactor.py", line 320, in install
+        reactor = AsyncioSelectorReactor(eventloop)
+      File "c:\projects\pytest-twisted\.tox\py38-asyncioreactor\lib\site-packages\twisted\internet\asyncioreactor.py", line 69, in __init__
+        super().__init__()
+      File "c:\projects\pytest-twisted\.tox\py38-asyncioreactor\lib\site-packages\twisted\internet\base.py", line 571, in __init__
+        self.installWaker()
+      File "c:\projects\pytest-twisted\.tox\py38-asyncioreactor\lib\site-packages\twisted\internet\posixbase.py", line 286, in installWaker
+        self.addReader(self.waker)
+      File "c:\projects\pytest-twisted\.tox\py38-asyncioreactor\lib\site-packages\twisted\internet\asyncioreactor.py", line 151, in addReader
+        self._asyncioEventloop.add_reader(fd, callWithLogger, reader,
+      File "C:\Python38-x64\Lib\asyncio\events.py", line 501, in add_reader
+        raise NotImplementedError
+    NotImplementedError
+
+The previous default, the selector loop, still works but you have to
+explicitly set it and do so early. The following ``conftest.py`` is provided
+for reference.
+
+.. code-block:: python3
+
+    import sys
+
+    import pytest
+    import pytest_twisted
+
+
+    @pytest.hookimpl(tryfirst=True)
+    def pytest_configure(config):
+        # https://twistedmatrix.com/trac/ticket/9766
+        # https://github.com/pytest-dev/pytest-twisted/issues/80
+
+        if (
+            config.getoption("reactor", "default") == "asyncio"
+            and sys.platform == 'win32'
+            and sys.version_info >= (3, 8)
+        ):
+            import asyncio
+
+            selector_policy = asyncio.WindowsSelectorEventLoopPolicy()
+            asyncio.set_event_loop_policy(selector_policy)
+
+
 Python 2 support plans
 ======================
 

appveyor.yml

@@ -26,6 +26,12 @@ environment:
     - TOXENV: py37-defaultreactor, win-py37-qt5reactor, py37-asyncioreactor
       PYTHON: "C:\\Python37-x64"
 
+    - TOXENV: py38-defaultreactor, win-py38-qt5reactor, py38-asyncioreactor
+      PYTHON: "C:\\Python38"
+
+    - TOXENV: py38-defaultreactor, win-py38-qt5reactor, py38-asyncioreactor
+      PYTHON: "C:\\Python38-x64"
+
 install:
   # https://github.com/pypa/virtualenv/issues/1050
   - pip install -U git+https://github.com/pypa/virtualenv@e8163e83a92c9098f51d390289323232ece15e3b

pytest_twisted.py

@@ -1,5 +1,6 @@
 import functools
 import inspect
+import sys
 import warnings
 
 import decorator
@@ -326,3 +327,18 @@ def pytest_configure(config):
     )(blockon)
 
     reactor_installers[config.getoption("reactor")]()
+
+
+def _use_asyncio_selector_if_required(config):
+    # https://twistedmatrix.com/trac/ticket/9766
+    # https://github.com/pytest-dev/pytest-twisted/issues/80
+
+    if (
+        config.getoption("reactor", "default") == "asyncio"
+        and sys.platform == 'win32'
+        and sys.version_info >= (3, 8)
+    ):
+        import asyncio
+
+        selector_policy = asyncio.WindowsSelectorEventLoopPolicy()
+        asyncio.set_event_loop_policy(selector_policy)

setup.py

@@ -28,6 +28,7 @@
         "Programming Language :: Python :: 3.5",
         "Programming Language :: Python :: 3.6",
         "Programming Language :: Python :: 3.7",
+        "Programming Language :: Python :: 3.8",
     ],
     entry_points={"pytest11": ["twisted = pytest_twisted"]},
 )

testing/conftest.py

@@ -1 +1,10 @@
+import pytest
+import pytest_twisted
+
+
 pytest_plugins = "_pytest.pytester"
+
+
+@pytest.hookimpl(tryfirst=True)
+def pytest_configure(config):
+    pytest_twisted._use_asyncio_selector_if_required(config=config)

testing/test_basic.py

@@ -49,6 +49,19 @@ def format_run_result_output_for_assert(run_result):
     )
 
 
+@pytest.fixture(name="default_conftest", autouse=True)
+def _default_conftest(testdir):
+    testdir.makeconftest(textwrap.dedent("""
+    import pytest
+    import pytest_twisted
+
+
+    @pytest.hookimpl(tryfirst=True)
+    def pytest_configure(config):
+        pytest_twisted._use_asyncio_selector_if_required(config=config)
+    """))
+
+
 def skip_if_reactor_not(request, expected_reactor):
     actual_reactor = request.config.getoption("reactor", "default")
     if actual_reactor != expected_reactor:
@@ -630,10 +643,14 @@ def main():
 def test_blockon_in_hook_with_asyncio(testdir, cmd_opts, request):
     skip_if_reactor_not(request, "asyncio")
     conftest_file = """
+    import pytest
     import pytest_twisted as pt
     from twisted.internet import defer
 
+    @pytest.hookimpl(tryfirst=True)
     def pytest_configure(config):
+        pt._use_asyncio_selector_if_required(config=config)
+
         pt.init_asyncio_reactor()
         d = defer.Deferred()
 
@@ -659,6 +676,14 @@ def test_succeed():
 def test_wrong_reactor_with_asyncio(testdir, cmd_opts, request):
     skip_if_reactor_not(request, "asyncio")
     conftest_file = """
+    import pytest
+    import pytest_twisted
+
+
+    @pytest.hookimpl(tryfirst=True)
+    def pytest_configure(config):
+        pytest_twisted._use_asyncio_selector_if_required(config=config)
+
     def pytest_addhooks():
         import twisted.internet.default
         twisted.internet.default.install()

tox.ini

@@ -1,8 +1,8 @@
 [tox]
 envlist=
     py{27,35}-defaultreactor
-    py{35,36,37}-{default,qt5,asyncio}reactor
-    win-py{35,36,37}-qt5reactor
+    py{35,36,37,38}-{default,qt5,asyncio}reactor
+    win-py{35,36,37,38}-qt5reactor
     linting
 
 [testenv]