Drop setuptools/pkg_resources dep; fix unhandled exceptions from hub.handle_error in a callback.

docs/changes/old_py.removal

 Remove support for obsolete Python versions. This is everything prior
 to 3.8.
+
+Related changes include:
+
+- Stop using ``pkg_resources`` to find entry points (plugins).
+  Instead, use ``importlib.metadata``.
+- Honor ``sys.unraisablehook`` when a callback function produces an
+  exception, and handling the exception in the hub *also* produces an
+  exception. In older versions, these would be simply printed.

setup.py

@@ -233,11 +233,6 @@ install_requires = greenlet_requires + CFFI_REQUIRES + [
     # ultimately be published, but at this writing only the event
     # interfaces are.
     'zope.interface',
-    # setuptools is also used (via pkg_resources) for event
-    # notifications. It's a hard dependency of zope.interface
-    # anyway.
-    # XXX: Drop this, shift to importlib.
-    'setuptools',
 ]
 
 # We use headers from greenlet, so it needs to be installed before we

src/gevent/__init__.py

@@ -62,25 +62,11 @@ if sys.platform == 'win32':
     import socket  # pylint:disable=unused-import,useless-suppression
     del socket
 
-try:
-    # Floating point number, in number of seconds,
-    # like time.time
-    getswitchinterval = sys.getswitchinterval
-    setswitchinterval = sys.setswitchinterval
-except AttributeError:
-    # Running on Python 2
-    _switchinterval = 0.005
-
-    def getswitchinterval():
-        return _switchinterval
-
-    def setswitchinterval(interval):
-        # Weed out None and non-numbers. This is not
-        # exactly exception compatible with the Python 3
-        # versions.
-        if interval > 0:
-            global _switchinterval
-            _switchinterval = interval
+
+# Floating point number, in number of seconds,
+# like time.time
+getswitchinterval = sys.getswitchinterval
+setswitchinterval = sys.setswitchinterval
 
 from gevent._config import config
 from gevent._hub_local import get_hub

src/gevent/events.py

@@ -20,6 +20,10 @@ much higher-level, flexible system. If you are using one of these
 systems, you generally will not want to directly modify `subscribers`.
 
 .. versionadded:: 1.3b1
+
+.. versionchanged:: NEXT
+   Now uses :mod:`importlib.metadata` instead of :mod:`pkg_resources`
+   to locate entry points.
 """
 from __future__ import absolute_import
 from __future__ import division
@@ -71,7 +75,7 @@ from zope.interface import implementer
 from zope.event import subscribers
 from zope.event import notify
 
-from pkg_resources import iter_entry_points
+
 
 #: Applications may register for notification of events by appending a
 #: callable to the ``subscribers`` list.
@@ -100,7 +104,36 @@ finally:
 
 def notify_and_call_entry_points(event):
     notify(event)
-    for plugin in iter_entry_points(event.ENTRY_POINT_NAME):
+    from importlib import metadata
+    import sys
+    # This used to use the  old ``pkg_resources.iter_entry_points(group,name=None)``
+    # API, passing it just the first argument, ``group=event.ENTRY_POINT_NAME``.
+    # In other words, we don't care about the ``name``.
+    if sys.version_info[:2] >= (3, 10):
+        # pylint:disable-next=unexpected-keyword-arg
+        # The only thing you can do with this is iterate it to get
+        # EntryPoint objects. (e.g., accessing by index raises a warning)
+        entry_points = metadata.entry_points(group=event.ENTRY_POINT_NAME)
+    else:
+        # Prior to 3.10, we have to do this all manually (keyword selection
+        # was introduced in 3.10; in 3.9 and before, entry_points returns a plain
+        # ``dict``). Using it like this is deprecated in 3.10, so to avoid warnings
+        # we have to write it twice.
+        #
+        # Prior to 3.9, there is no ``.module`` attribute, so if we
+        # needed that we'd have to look at the complete ``.value``
+        # attribute.
+        ep_dict = entry_points()
+        __traceback_info__ = ep_dict
+        # On Python 3.8, we can get duplicate EntryPoint objects; it is unclear
+        # why. Drop them into a set to make sure we only get one.
+        entry_points = set(
+            ep
+            for ep
+            in ep_dict.get(event.ENTRY_POINT_NAME)
+        )
+
+    for plugin in entry_points:
         subscriber = plugin.load()
         subscriber(event)
 

src/gevent/libev/corecext.pyx

@@ -30,12 +30,17 @@ from cpython.ref cimport Py_INCREF
 from cpython.ref cimport Py_DECREF
 from cpython.mem cimport PyMem_Malloc
 from cpython.mem cimport PyMem_Free
+from cpython.object cimport PyObject
+from cpython.exc cimport PyErr_NormalizeException
+from cpython.exc cimport PyErr_WriteUnraisable
 from libc.errno cimport errno
 
 cdef extern from "Python.h":
     int    Py_ReprEnter(object)
     void   Py_ReprLeave(object)
 
+    int PyException_SetTraceback(PyObject* ex, PyObject* tb) except *
+
 import sys
 import os
 import traceback
@@ -1387,12 +1392,15 @@ cdef public void gevent_handle_error(loop loop, object context):
     # If it was set, this will clear it, and we will own
     # the references.
     PyErr_Fetch(&typep, &valuep, &tracebackp)
-    # TODO: Should we call PyErr_Normalize? There's code in
-    # Hub.handle_error that works around what looks like an
-    # unnormalized exception.
-
     if not typep:
         return
+
+    PyErr_NormalizeException(&typep, &valuep, &tracebackp)
+
+
+    if tracebackp:
+        PyException_SetTraceback(valuep, tracebackp)
+
     # This assignment will do a Py_INCREF
     # on the value. We already own the reference
     # returned from PyErr_Fetch,
@@ -1410,7 +1418,15 @@ cdef public void gevent_handle_error(loop loop, object context):
     # If this method fails by raising an exception,
     # cython will print it for us because we don't return a
     # Python object and we don't declare an `except` clause.
-    loop.handle_error(context, type, value, traceback)
+    # Prior to Cython 3.<something>, we relied on Cython printing an
+    # uncaught exception here (because we don't return a Python object, and
+    # we have no except clause). It seems that as-of 3.0b3 at least,
+    # that no longer happens by default; if we want un caught, unraisable exception to be
+    # reported, we need to do so ourself.
+    try:
+        loop.handle_error(context, type, value, traceback)
+    except:
+        PyErr_WriteUnraisable(context)
 
 cdef public tuple _empty_tuple = ()
 

src/gevent/testing/patched_tests_setup.py

@@ -115,6 +115,17 @@ def get_switch_expected(fullname):
 
 
 disabled_tests = [
+    # "test an implementation detail of thread objects" --- our implementation differs
+    "test_threading.ThreadTests.test_tstate_lock",
+    # This likes to check the number of native thread IDs using the ``native_id`` attribute,
+    # and the ``get_native_id()`` function. Because we're monkey-patched,
+    # those don't change in other threads, so it won't work.
+    'test_threading.ThreadTests.test_various_ops',
+    # Added to address CPython issue 27718; it wants functions in the signal
+    # module to have __module__ equal to 'signal', but obviously when we
+    # monkey patch they don't.
+    'test_signal.GenericTests.test_functions_module_attr',
+
     # XXX: While we debug latest updates. This is leaking
     'test_threading.ThreadTests.test_no_refcycle_through_target',
 

src/gevent/testing/sysinfo.py

@@ -209,9 +209,9 @@ def libev_supports_linux_iouring():
 
 def resolver_dnspython_available():
     # Try hard not to leave around junk we don't have to.
-    import pkg_resources
+    from importlib import metadata
     try:
-        pkg_resources.get_distribution('dnspython')
-    except pkg_resources.DistributionNotFound:
+        metadata.distribution('dnspython')
+    except metadata.PackageNotFoundError:
         return False
     return True