bpo-47167: Allow overriding a future compliance check in asyncio.Task (GH-32197)

2 files changed, 102 insertions, 8 deletions

diff --git a/Modules/_asynciomodule.c b/Modules/_asynciomodule.c
index 632a446..d8d3da9 100644
--- a/Modules/_asynciomodule.c
+++ b/Modules/_asynciomodule.c
@@ -23,6 +23,7 @@ _Py_IDENTIFIER(call_soon);
 _Py_IDENTIFIER(cancel);
 _Py_IDENTIFIER(get_event_loop);
 _Py_IDENTIFIER(throw);
+_Py_IDENTIFIER(_check_future);
 
 
 /* State of the _asyncio module */
@@ -1795,6 +1796,8 @@ class _asyncio.Task "TaskObj *" "&Task_Type"
 static int task_call_step_soon(TaskObj *, PyObject *);
 static PyObject * task_wakeup(TaskObj *, PyObject *);
 static PyObject * task_step(TaskObj *, PyObject *);
+static int task_check_future(TaskObj *, PyObject *);
+static int task_check_future_exact(TaskObj *, PyObject *);
 
 /* ----- Task._step wrapper */
 
@@ -2269,7 +2272,6 @@ Returns the remaining number of cancellation requests.
 static PyObject *
 _asyncio_Task_uncancel_impl(TaskObj *self)
 /*[clinic end generated code: output=58184d236a817d3c input=68f81a4b90b46be2]*/
-/*[clinic end generated code]*/
 {
     if (self->task_num_cancels_requested > 0) {
         self->task_num_cancels_requested -= 1;
@@ -2278,6 +2280,21 @@ _asyncio_Task_uncancel_impl(TaskObj *self)
 }
 
 /*[clinic input]
+_asyncio.Task._check_future -> bool
+
+    future: object
+
+Return False if task and future loops are not compatible.
+[clinic start generated code]*/
+
+static int
+_asyncio_Task__check_future_impl(TaskObj *self, PyObject *future)
+/*[clinic end generated code: output=a3bfba79295c8d57 input=3b1d6dfd6fe90aa5]*/
+{
+    return task_check_future_exact(self, future);
+}
+
+/*[clinic input]
 _asyncio.Task.get_stack
 
     *
@@ -2502,6 +2519,7 @@ static PyMethodDef TaskType_methods[] = {
     _ASYNCIO_TASK_CANCEL_METHODDEF
     _ASYNCIO_TASK_CANCELLING_METHODDEF
     _ASYNCIO_TASK_UNCANCEL_METHODDEF
+    _ASYNCIO_TASK__CHECK_FUTURE_METHODDEF
     _ASYNCIO_TASK_GET_STACK_METHODDEF
     _ASYNCIO_TASK_PRINT_STACK_METHODDEF
     _ASYNCIO_TASK__MAKE_CANCELLED_ERROR_METHODDEF
@@ -2570,6 +2588,43 @@ TaskObj_dealloc(PyObject *self)
 }
 
 static int
+task_check_future_exact(TaskObj *task, PyObject *future)
+{
+    int res;
+    if (Future_CheckExact(future) || Task_CheckExact(future)) {
+        FutureObj *fut = (FutureObj *)future;
+        res = (fut->fut_loop == task->task_loop);
+    } else {
+        PyObject *oloop = get_future_loop(future);
+        if (oloop == NULL) {
+            return -1;
+        }
+        res = (oloop == task->task_loop);
+        Py_DECREF(oloop);
+    }
+    return res;
+}
+
+
+static int
+task_check_future(TaskObj *task, PyObject *future)
+{
+    if (Task_CheckExact(task)) {
+        return task_check_future_exact(task, future);
+    } else {
+        PyObject * ret = _PyObject_CallMethodIdOneArg((PyObject *)task,
+                                                      &PyId__check_future,
+                                                      future);
+        if (ret == NULL) {
+            return -1;
+        }
+        int is_true = PyObject_IsTrue(ret);
+        Py_DECREF(ret);
+        return is_true;
+    }
+}
+
+static int
 task_call_step_soon(TaskObj *task, PyObject *arg)
 {
     PyObject *cb = TaskStepMethWrapper_new(task, arg);
@@ -2790,7 +2845,11 @@ task_step_impl(TaskObj *task, PyObject *exc)
         FutureObj *fut = (FutureObj*)result;
 
         /* Check if `result` future is attached to a different loop */
-        if (fut->fut_loop != task->task_loop) {
+        res = task_check_future(task, result);
+        if (res == -1) {
+            goto fail;
+        }
+        if (res == 0) {
             goto different_loop;
         }
 
@@ -2862,15 +2921,13 @@ task_step_impl(TaskObj *task, PyObject *exc)
         }
 
         /* Check if `result` future is attached to a different loop */
-        PyObject *oloop = get_future_loop(result);
-        if (oloop == NULL) {
+        res = task_check_future(task, result);
+        if (res == -1) {
             goto fail;
         }
-        if (oloop != task->task_loop) {
-            Py_DECREF(oloop);
+        if (res == 0) {
             goto different_loop;
         }
-        Py_DECREF(oloop);
 
         if (!blocking) {
             goto yield_insteadof_yf;
diff --git a/Modules/clinic/_asynciomodule.c.h b/Modules/clinic/_asynciomodule.c.h
index 4b64367..163b0f9 100644
--- a/Modules/clinic/_asynciomodule.c.h
+++ b/Modules/clinic/_asynciomodule.c.h
@@ -466,6 +466,43 @@ _asyncio_Task_uncancel(TaskObj *self, PyObject *Py_UNUSED(ignored))
     return _asyncio_Task_uncancel_impl(self);
 }
 
+PyDoc_STRVAR(_asyncio_Task__check_future__doc__,
+"_check_future($self, /, future)\n"
+"--\n"
+"\n"
+"Return False if task and future loops are not compatible.");
+
+#define _ASYNCIO_TASK__CHECK_FUTURE_METHODDEF    \
+    {"_check_future", (PyCFunction)(void(*)(void))_asyncio_Task__check_future, METH_FASTCALL|METH_KEYWORDS, _asyncio_Task__check_future__doc__},
+
+static int
+_asyncio_Task__check_future_impl(TaskObj *self, PyObject *future);
+
+static PyObject *
+_asyncio_Task__check_future(TaskObj *self, PyObject *const *args, Py_ssize_t nargs, PyObject *kwnames)
+{
+    PyObject *return_value = NULL;
+    static const char * const _keywords[] = {"future", NULL};
+    static _PyArg_Parser _parser = {NULL, _keywords, "_check_future", 0};
+    PyObject *argsbuf[1];
+    PyObject *future;
+    int _return_value;
+
+    args = _PyArg_UnpackKeywords(args, nargs, NULL, kwnames, &_parser, 1, 1, 0, argsbuf);
+    if (!args) {
+        goto exit;
+    }
+    future = args[0];
+    _return_value = _asyncio_Task__check_future_impl(self, future);
+    if ((_return_value == -1) && PyErr_Occurred()) {
+        goto exit;
+    }
+    return_value = PyBool_FromLong((long)_return_value);
+
+exit:
+    return return_value;
+}
+
 PyDoc_STRVAR(_asyncio_Task_get_stack__doc__,
 "get_stack($self, /, *, limit=None)\n"
 "--\n"
@@ -890,4 +927,4 @@ _asyncio__leave_task(PyObject *module, PyObject *const *args, Py_ssize_t nargs,
 exit:
     return return_value;
 }
-/*[clinic end generated code: output=64b3836574e8a18c input=a9049054013a1b77]*/
+/*[clinic end generated code: output=fdb7129263a8712e input=a9049054013a1b77]*/