From: Andrew Svetlov <andrew.svetlov@gmail.com>
Date: Tue, 17 Sep 2019 12:59:49 +0000 (+0300)
Subject: bpo-38013: make async_generator_athrow object tolerant to throwing exceptions (GH... 
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=c275312a6284bd319ea33c9abd7e15c230eca43f;p=python

bpo-38013: make async_generator_athrow object tolerant to throwing exceptions (GH-16070)



Even when the helper is not started yet.

This behavior follows conventional generator one.
There is no reason for `async_generator_athrow` to handle `gen.throw()` differently.



https://bugs.python.org/issue38013
---

diff --git a/Lib/test/test_asyncgen.py b/Lib/test/test_asyncgen.py
index 71b0968c79..3a8d5fd400 100644
--- a/Lib/test/test_asyncgen.py
+++ b/Lib/test/test_asyncgen.py
@@ -1125,6 +1125,28 @@ class AsyncGenAsyncioTest(unittest.TestCase):
         res = self.loop.run_until_complete(run())
         self.assertEqual(res, [i * 2 for i in range(1, 10)])
 
+    def test_asyncgen_nonstarted_hooks_are_cancellable(self):
+        # See https://bugs.python.org/issue38013
+        messages = []
+
+        def exception_handler(loop, context):
+            messages.append(context)
+
+        async def async_iterate():
+            yield 1
+            yield 2
+
+        async def main():
+            loop = asyncio.get_running_loop()
+            loop.set_exception_handler(exception_handler)
+
+            async for i in async_iterate():
+                break
+
+        asyncio.run(main())
+
+        self.assertEqual([], messages)
+
 
 if __name__ == "__main__":
     unittest.main()
diff --git a/Misc/NEWS.d/next/Core and Builtins/2019-09-12-19-50-01.bpo-38013.I7btD0.rst b/Misc/NEWS.d/next/Core and Builtins/2019-09-12-19-50-01.bpo-38013.I7btD0.rst
new file mode 100644
index 0000000000..a61aa48ff1
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2019-09-12-19-50-01.bpo-38013.I7btD0.rst	
@@ -0,0 +1,3 @@
+Allow to call ``async_generator_athrow().throw(...)`` even for non-started
+async generator helper. It fixes annoying warning at the end of
+:func:`asyncio.run` call.
diff --git a/Objects/genobject.c b/Objects/genobject.c
index 9f490b4e2e..82e6e55868 100644
--- a/Objects/genobject.c
+++ b/Objects/genobject.c
@@ -1884,11 +1884,6 @@ async_gen_athrow_throw(PyAsyncGenAThrow *o, PyObject *args)
 {
     PyObject *retval;
 
-    if (o->agt_state == AWAITABLE_STATE_INIT) {
-        PyErr_SetString(PyExc_RuntimeError, NON_INIT_CORO_MSG);
-        return NULL;
-    }
-
     if (o->agt_state == AWAITABLE_STATE_CLOSED) {
         PyErr_SetNone(PyExc_StopIteration);
         return NULL;