Stackless issue #190: Do not close running (async) generators or coroutines (#195)

Silently ignore attempts to close a running generator, coroutine or asynchronous
generator. This avoids spurious error messages, if such an object is deallocated
as part of a paused, restorable tasklet.

Author: Anselm Kruis

Objects/genobject.c

@@ -173,6 +173,15 @@ gen_send_ex(PyGenObject *gen, PyObject *arg, int exc, int closing)
     PyFrameObject *f = gen->gi_frame;
     PyObject *result;
 
+#ifdef STACKLESS
+    if (gen->gi_running && exc && closing) {
+        /*
+         * Do not close a running generator.
+         * See Stackless issue 190.
+         */
+        return NULL;
+    }
+#endif
     if (gen->gi_running) {
         const char *msg = "generator already executing";
         if (PyCoro_CheckExact(gen)) {

Stackless/changelog.txt

@@ -9,6 +9,11 @@ What's New in Stackless 3.X.X?
 
 *Release date: 20XX-XX-XX*
 
+- https://github.com/stackless-dev/stackless/issues/190
+  Silently ignore attempts to close a running generator, coroutine or
+  asynchronous generator. This avoids spurious error messages, if such an
+  object is deallocated as part of a paused, restorable tasklet.
+
 - https://github.com/stackless-dev/stackless/issues/193
   Fix the macros PyTasklet_CheckExact(op) and PyChannel_CheckExact(op).
   Previously they contained a reference to a non existing variable.

Stackless/unittests/test_generator.py

@@ -8,7 +8,7 @@
 import sys
 
 from support import test_main  # @UnusedImport
-from support import StacklessTestCase
+from support import StacklessTestCase, captured_stderr
 
 
 def f():
@@ -37,6 +37,74 @@ def testSimpleLeakage(self):
         if len(leakage):
             self.failUnless(len(leakage) == 0, "Leaked %s" % repr(leakage))
 
+    def run_GC_test(self, task, arg):
+        tasklet = stackless.tasklet(task)(arg)
+        tasklet.run()
+        if False:  # To test the generator / coroutine / async gen
+            tasklet.run()
+            self.assertFalse(tasklet.alive)
+            return
+        self.assertTrue(tasklet.paused)
+        tasklet.tempval = None
+        with captured_stderr() as stringio:
+            # must not throw or output
+            if tasklet.restorable:
+                tasklet.bind(None)
+            # make sure, that t=None kills the last reference
+            self.assertEqual(sys.getrefcount(tasklet), 2)
+            tasklet = None
+        self.assertEqual(stringio.getvalue(), "")
+
+    def testGCRunningGenerator(self):
+        def gen():
+            try:
+                # print("gen nesting level: ", stackless.current.nesting_level)
+                stackless.schedule_remove()
+                yield 1
+            except:  # @IgnorePep8
+                # print("exception in gen:", sys.exc_info())
+                raise
+
+        def task(generator):
+            l = [i for i in generator]
+            self.assertListEqual(l, [1])
+
+        self.run_GC_test(task,gen())
+
+    def testGCRunningCoroutine(self):
+        async def coro():
+            try:
+                # print("coro nesting level: ", stackless.current.nesting_level)
+                stackless.schedule_remove()
+            except:  # @IgnorePep8
+                # print("exception in coro:", sys.exc_info())
+                raise
+
+        def task(c):
+            self.assertRaises(StopIteration, c.send, None)
+
+        self.run_GC_test(task, coro())
+
+    def testGCRunningAsyncGen(self):
+        async def asyncgen():
+            try:
+                # print("asyncgen nesting level: ", stackless.current.nesting_level)
+                stackless.schedule_remove()
+            except:  # @IgnorePep8
+                # print("exception in asyncgen:", sys.exc_info())
+                raise
+            yield 100
+
+        def task(ag):
+            c = ag.__anext__()
+            with self.assertRaises(StopIteration) as cm:
+                c.send(None)
+            self.assertEqual(cm.exception.value, 100)
+            c = ag.__anext__()
+            self.assertRaises(StopAsyncIteration, c.send, None)
+
+        self.run_GC_test(task, asyncgen())
+
 
 class TestGeneratorWrapper(StacklessTestCase):
     def test_run_wrap_generator(self):