Initial fixes to enable basic tests to run on Python 3.7a1.

src/gevent/monkey.py

@@ -506,6 +506,7 @@ def patch_select(aggressive=True):
     - :class:`selectors.KqueueSelector`
     - :class:`selectors.DevpollSelector` (Python 3.5+)
     """
+
     patch_module('select')
     if aggressive:
         select = __import__('select')
@@ -536,6 +537,14 @@ def patch_select(aggressive=True):
             selectors.SelectSelector._select = _select
             _select._gevent_monkey = True
 
+        # Python 3.7 refactors the poll-like selectors to use a common
+        # base class and capture a reference to select.poll, etc, at
+        # import time. selectors tends to get imported early
+        # (importing 'platform' does it: platform -> subprocess -> selectors),
+        # so we need to clean that up.
+        if hasattr(selectors, 'PollSelector') and hasattr(selectors.PollSelector, '_selector_cls'):
+            selectors.PollSelector._selector_cls = select.poll
+
         if aggressive:
             # If `selectors` had already been imported before we removed
             # select.epoll|kqueue|devpoll, these may have been defined in terms

src/greentest/greentest.py

@@ -769,6 +769,8 @@ def default_get_number_open_files():
 lsof_get_open_files = default_get_open_files
 
 try:
+    # psutil import subprocess which on Python 3 imports selectors.
+    # This can expose issues with monkey-patching.
     import psutil
 except ImportError:
     get_open_files = default_get_open_files

src/greentest/patched_tests_setup.py

@@ -6,11 +6,15 @@ import contextlib
 import functools
 import sys
 import os
-import platform
+# At least on 3.6+, importing platform
+# imports subprocess, which imports selectors. That
+# can expose issues with monkey patching. We don't need it
+# though.
+# import platform
 import re
 
 TRAVIS = os.environ.get("TRAVIS") == "true"
-OSX = bool(platform.mac_ver()[0])
+OSX = sys.platform == 'darwin'
 
 # By default, test cases are expected to switch and emit warnings if there was none
 # If a test is found in this list, it's expected not to switch.

src/greentest/test_threading_2.py

@@ -470,7 +470,6 @@ class ThreadJoinOnShutdown(unittest.TestCase):
             """
         self._run_and_join(script)
 
-    @greentest.skipOnPyPy3("Buffering issue.")
     def test_3_join_in_forked_from_thread(self):
         # Like the test above, but fork() was called from a worker thread
         # In the forked process, the main Thread object must be marked as stopped.
@@ -500,13 +499,17 @@ class ThreadJoinOnShutdown(unittest.TestCase):
 
             w = threading.Thread(target=worker)
             w.start()
+            import sys
+            if sys.version_info[:2] >= (3, 7) or (sys.version_info[:2] >= (3, 5) and hasattr(sys, 'pypy_version_info')):
+                w.join()
             """
         # In PyPy3 5.8.0, if we don't wait on this top-level "thread", 'w',
         # we never see "end of thread". It's not clear why, since that's being
         # done in a child of this process. Yet in normal CPython 3, waiting on this
         # causes the whole process to lock up (possibly because of some loop within
         # the interpreter waiting on thread locks, like the issue described in threading.py
-        # for Python 3.4? in any case, it doesn't hang in Python 2.)
+        # for Python 3.4? in any case, it doesn't hang in Python 2.) This changed in
+        # 3.7a1 and waiting on it is again necessary and doesn't hang.
         self._run_and_join(script)