Make zope.interface/event and setuptools required dependencies.

Fixes #1619

docs/changes/1619.feature

+Make ``zope.interface``, ``zope.event`` and (by extension)
+``setuptools`` required dependencies. The ``events`` install extra now
+does nothing and will be removed in 2021.

docs/install.rst

@@ -117,8 +117,7 @@ fall back to doing this if no binary wheel is available. See
 Extra Dependencies
 ==================
 
-gevent has no runtime dependencies outside the standard library,
-greenlet, and (on some platforms) `cffi`_. However, there are a number
+There are a number
 of additional libraries that extend gevent's functionality and will be
 used if they are available. All of these may be installed using
 `setuptools extras
@@ -126,9 +125,13 @@ used if they are available. All of these may be installed using
 as named below, e.g., ``pip install gevent[events]``.
 
 events
-    Configurable event support using `zope.event
-    <https://pypi.org/project/zope.event>`_ is highly recommended for
-    configurable event support.
+    In versions of gevent up to and including 20.5.0, this provided configurable
+    event support using `zope.event
+    <https://pypi.org/project/zope.event>`_ and was highly
+    recommended.
+
+    In versions after that, this extra is empty and does nothing. It
+    will be removed in gevent 21.0.
 
 dnspython
     Enables the new pure-Python resolver, backed by `dnspython

setup.py

@@ -211,7 +211,18 @@ CFFI_REQUIRES = [
 ]
 
 
-install_requires = greenlet_requires + CFFI_REQUIRES
+install_requires = greenlet_requires + CFFI_REQUIRES + [
+    # For event notification.
+    'zope.event',
+    # For event definitions, and our own interfaces; those should
+    # 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.
+    'setuptools',
+]
 
 # We use headers from greenlet, so it needs to be installed before we
 # can compile. If it isn't already installed before we start
@@ -284,8 +295,9 @@ EXTRA_DNSPYTHON = [
     'idna',
 ]
 EXTRA_EVENTS = [
-    'zope.event',
-    'zope.interface',
+    # No longer does anything, but the extra must stay around
+    # to avoid breaking install scripts.
+    # Remove this in 2021.
 ]
 
 EXTRA_PSUTIL_DEPS = [

src/gevent/_interfaces.py

@@ -16,10 +16,11 @@ from __future__ import print_function
 
 import sys
 
-from gevent._util import Interface
-from gevent._util import Attribute
+from zope.interface import Interface
+from zope.interface import Attribute
 
 # pylint:disable=no-method-argument, unused-argument, no-self-argument
+# pylint:disable=inherit-non-class
 
 __all__ = [
     'ILoop',

src/gevent/_util.py

@@ -206,25 +206,6 @@ def gmctime():
     import time
     return time.strftime("%Y-%m-%dT%H:%M:%SZ", time.gmtime())
 
-try:
-    from zope.interface import Interface
-    from zope.interface import implementer
-    from zope.interface import Attribute
-except ImportError:
-    class Interface(object):
-        pass
-    def implementer(_iface):
-        def dec(c):
-            return c
-        return dec
-
-    def Attribute(s):
-        return s
-
-Interface = Interface
-implementer = implementer
-Attribute = Attribute
-
 
 ###
 # Release automation.

src/gevent/events.py

@@ -11,13 +11,13 @@ parameter, the event object).
 Higher level frameworks may take this foundation and build richer
 models on it.
 
-If :mod:`zope.event` is installed, then it will be used to provide the
-functionality of `notify` and `subscribers`. See
-:mod:`zope.event.classhandler` for a simple class-based approach to
-subscribing to a filtered list of events, and see `zope.component
+:mod:`zope.event` will be used to provide the functionality of
+`notify` and `subscribers`. See :mod:`zope.event.classhandler` for a
+simple class-based approach to subscribing to a filtered list of
+events, and see `zope.component
 <https://zopecomponent.readthedocs.io/en/latest/event.html>`_ for a
-much higher-level, flexible system. If you are using one of these systems,
-you generally will not want to directly modify `subscribers`.
+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
 """
@@ -61,61 +61,49 @@ __all__ = [
     'GeventDidPatchAllEvent',
 ]
 
-# pylint:disable=no-self-argument
+# pylint:disable=no-self-argument,inherit-non-class
+import platform
 
-try:
-    from zope.event import subscribers
-    from zope.event import notify
-except ImportError:
-    #: Applications may register for notification of events by appending a
-    #: callable to the ``subscribers`` list.
-    #:
-    #: Each subscriber takes a single argument, which is the event object
-    #: being published.
-    #:
-    #: Exceptions raised by subscribers will be propagated *without* running
-    #: any remaining subscribers.
-    subscribers = []
-
-    def notify(event):
-        """
-        Notify all subscribers of ``event``.
-        """
-        for subscriber in subscribers:
-            subscriber(event)
+from zope.interface import Interface
+from zope.interface import Attribute
+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.
+#:
+#: Each subscriber takes a single argument, which is the event object
+#: being published.
+#:
+#: Exceptions raised by subscribers will be propagated *without* running
+#: any remaining subscribers.
+#:
+#: This is an alias for `zope.event.subscribers`; prefer to use
+#: that attribute directly.
+subscribers = subscribers
 
-notify = notify # export
 try:
-    # pkg_resources is technically optional, we don't
-    # list a hard dependency on it.
-    __import__('pkg_resources')
-except ImportError:
-    notify_and_call_entry_points = notify
-else:
-    from pkg_resources import iter_entry_points
-    import platform
-    try:
     # Cache the platform info. pkg_resources uses
     # platform.machine() for environment markers, and
     # platform.machine() wants to call os.popen('uname'), which is
     # broken on Py2 when the gevent child signal handler is
     # installed. (see test__monkey_sigchild_2.py)
     platform.uname()
-    except: # pylint:disable=bare-except
+except: # pylint:disable=bare-except
     pass
-    finally:
+finally:
     del platform
 
-    def notify_and_call_entry_points(event):
+def notify_and_call_entry_points(event):
     notify(event)
     for plugin in iter_entry_points(event.ENTRY_POINT_NAME):
         subscriber = plugin.load()
         subscriber(event)
 
-from gevent._util import Interface
-from gevent._util import implementer
-from gevent._util import Attribute
-
 
 class IPeriodicMonitorThread(Interface):
     """

src/gevent/libev/corecffi.py

@@ -14,7 +14,8 @@ __all__ = [
     'loop',
 ]
 
-from gevent._util import implementer
+from zope.interface import implementer
+
 from gevent._interfaces import ILoop
 
 from gevent.libev import _corecffi # pylint:disable=no-name-in-module,import-error

src/gevent/libuv/loop.py

@@ -10,6 +10,8 @@ from collections import namedtuple
 from operator import delitem
 import signal
 
+from zope.interface import implementer
+
 from gevent import getcurrent
 from gevent.exceptions import LoopExit
 
@@ -17,7 +19,6 @@ from gevent._ffi import _dbg # pylint: disable=unused-import
 from gevent._ffi.loop import AbstractLoop
 from gevent._ffi.loop import assign_standard_callbacks
 from gevent._ffi.loop import AbstractCallbacks
-from gevent._util import implementer
 from gevent._interfaces import ILoop
 from gevent.libuv import _corecffi # pylint:disable=no-name-in-module,import-error
 

src/gevent/tests/test__local.py

@@ -7,6 +7,8 @@ from gevent import monkey; monkey.patch_all()
 from threading import local
 from threading import Thread
 
+from zope import interface
+
 try:
     from collections.abc import Mapping
 except ImportError:
@@ -379,12 +381,7 @@ class TestGeventLocal(greentest.TestCase):
         x = LocalWithClassMethod()
         self.assertIs(LocalWithClassMethod, x.a_classmethod())
 
-try:
-    from zope import interface
-except ImportError:
-    interface = None
 
-@greentest.skipIf(interface is None, "Needs zope.interface")
 class TestLocalInterface(greentest.TestCase):
     __timeout__ = None