Make the CFFI backend handle the watcher's args property more like the Cython...

Make the CFFI backend handle the watcher's args property more like the Cython backend. Fixes test__core_watcher.

changelog.rst

@@ -23,7 +23,17 @@
 - :func:`gevent.spawn_raw` now accepts keyword arguments, as
   previously (incorrectly) documented. Reported in :issue:`680` by Ron
   Rothman.
-- PyPy: PyPy 2.6.1 or later is now required (4.0.1 or later is recommended).
+- PyPy: PyPy 2.6.1 or later is now required (4.0.1 or later is
+  recommended).
+- The CFFI backend is now built and usable on CPython implementations
+  (except on Windows) if ``cffi`` is installed before gevent is
+  installed. To use the CFFI backend, set the environment variable
+  ``GEVENT_CORE_CFFI_ONLY`` before starting Python. This can aid
+  debugging in some cases and helps ensure parity across all
+  combinations of supported platforms.
+- The CFFI backend now call the callback of a watcher whose ``args`` attribute is
+  set to ``None``, just like the Cython backend does. It also only
+  allows ``args`` to be a tuple or ``None``, again matching the Cython backend.
 
 1.1rc1 (Nov 14, 2015)
 =====================

gevent/corecffi.py

@@ -108,9 +108,14 @@ def _python_callback(handle, revents):
         # is not what we want; that can permanently wedge the loop depending
         # on which callback was executing
         watcher = ffi.from_handle(handle)
-        if len(watcher.args) > 0 and watcher.args[0] == GEVENT_CORE_EVENTS:
-            watcher.args = (revents, ) + watcher.args[1:]
-        watcher.callback(*watcher.args)
+        args = watcher.args
+        if args is None:
+            # Legacy behaviour from corecext: convert None into ()
+            # See test__core_watcher.py
+            args = _NOARGS
+        if len(args) > 0 and args[0] == GEVENT_CORE_EVENTS:
+            args = (revents, ) + args[1:]
+        watcher.callback(*args)
     except:
         watcher._exc_info = sys.exc_info()
         # Depending on when the exception happened, the watcher
@@ -711,7 +716,7 @@ class watcher(object):
             self._flags = 0
         else:
             self._flags = 4
-        self.args = None
+        self._args = None
         self._callback = None
         self._handle = ffi.new_handle(self)
         self._gwatcher = ffi.new(self._watcher_struct_pointer_type)
@@ -812,6 +817,16 @@ class watcher(object):
         self._callback = cb
     callback = property(_get_callback, _set_callback)
 
+    def _get_args(self):
+        return self._args
+
+    def _set_args(self, args):
+        if not isinstance(args, tuple) and args is not None:
+            raise TypeError("args must be a tuple or None")
+        self._args = args
+
+    args = property(_get_args, _set_args)
+
     def start(self, callback, *args):
         if callback is None:
             raise TypeError('callback must be callable, not None')

greentest/test__core_watcher.py

@@ -30,28 +30,16 @@ class Test(greentest.TestCase):
             pass
         # test that args can be changed later
         io.args = (1, 2, 3)
-        if greentest.PYPY:
-            pass  # on PYPY .args is just a normal property
-        else:
-            # test that only tuple and None are accepted by 'args' attribute
-            try:
-                io.args = 5
-                raise AssertionError('"io.args = 5" must raise TypeError')
-            except TypeError:
-                pass
-            self.assertEqual(io.args, (1, 2, 3))
-            try:
-                io.args = [4, 5]
-                raise AssertionError('"io.args = [4, 5]" must raise TypeError')
-            except TypeError:
-                pass
+        # test that only tuple and None are accepted by 'args' attribute
+        self.assertRaises(TypeError, setattr, io, 'args', 5)
         self.assertEqual(io.args, (1, 2, 3))
-        if greentest.PYPY:
-            io.args = ()
-        else:
-            # None also works, means empty tuple
-            # XXX why?
-            io.args = None
+
+        self.assertRaises(TypeError, setattr, io, 'args', [4, 5])
+        self.assertEqual(io.args, (1, 2, 3))
+        # None also works, means empty tuple
+        # XXX why?
+        io.args = None
+        self.assertEqual(io.args, None)
         start = core.time()
         loop.run()
         took = core.time() - start