bpo-39529: Deprecate creating new event loop in asyncio.get_event_loop() (GH-23554)

asyncio.get_event_loop() emits now a deprecation warning when it creates a new event loop.
In future releases it will became an alias of asyncio.get_running_loop().

2 files changed, 63 insertions, 4 deletions

diff --git a/Modules/_asynciomodule.c b/Modules/_asynciomodule.c
index 01e36c6..a4d5d45 100644
--- a/Modules/_asynciomodule.c
+++ b/Modules/_asynciomodule.c
@@ -319,7 +319,7 @@ set_running_loop(PyObject *loop)
 
 
 static PyObject *
-get_event_loop(void)
+get_event_loop(int stacklevel)
 {
     PyObject *loop;
     PyObject *policy;
@@ -331,6 +331,13 @@ get_event_loop(void)
         return loop;
     }
 
+    if (PyErr_WarnEx(PyExc_DeprecationWarning,
+                     "There is no current event loop",
+                     stacklevel))
+    {
+        return NULL;
+    }
+
     policy = PyObject_CallNoArgs(asyncio_get_event_loop_policy);
     if (policy == NULL) {
         return NULL;
@@ -489,7 +496,7 @@ future_init(FutureObj *fut, PyObject *loop)
     fut->fut_blocking = 0;
 
     if (loop == Py_None) {
-        loop = get_event_loop();
+        loop = get_event_loop(1);
         if (loop == NULL) {
             return -1;
         }
@@ -3078,7 +3085,19 @@ static PyObject *
 _asyncio_get_event_loop_impl(PyObject *module)
 /*[clinic end generated code: output=2a2d8b2f824c648b input=9364bf2916c8655d]*/
 {
-    return get_event_loop();
+    return get_event_loop(1);
+}
+
+/*[clinic input]
+_asyncio._get_event_loop
+    stacklevel: int = 3
+[clinic start generated code]*/
+
+static PyObject *
+_asyncio__get_event_loop_impl(PyObject *module, int stacklevel)
+/*[clinic end generated code: output=9c1d6d3c802e67c9 input=d17aebbd686f711d]*/
+{
+    return get_event_loop(stacklevel-1);
 }
 
 /*[clinic input]
@@ -3375,6 +3394,7 @@ PyDoc_STRVAR(module_doc, "Accelerator module for asyncio");
 
 static PyMethodDef asyncio_methods[] = {
     _ASYNCIO_GET_EVENT_LOOP_METHODDEF
+    _ASYNCIO__GET_EVENT_LOOP_METHODDEF
     _ASYNCIO_GET_RUNNING_LOOP_METHODDEF
     _ASYNCIO__GET_RUNNING_LOOP_METHODDEF
     _ASYNCIO__SET_RUNNING_LOOP_METHODDEF
diff --git a/Modules/clinic/_asynciomodule.c.h b/Modules/clinic/_asynciomodule.c.h
index a071efc..c472e65 100644
--- a/Modules/clinic/_asynciomodule.c.h
+++ b/Modules/clinic/_asynciomodule.c.h
@@ -669,6 +669,45 @@ _asyncio_get_event_loop(PyObject *module, PyObject *Py_UNUSED(ignored))
     return _asyncio_get_event_loop_impl(module);
 }
 
+PyDoc_STRVAR(_asyncio__get_event_loop__doc__,
+"_get_event_loop($module, /, stacklevel=3)\n"
+"--\n"
+"\n");
+
+#define _ASYNCIO__GET_EVENT_LOOP_METHODDEF    \
+    {"_get_event_loop", (PyCFunction)(void(*)(void))_asyncio__get_event_loop, METH_FASTCALL|METH_KEYWORDS, _asyncio__get_event_loop__doc__},
+
+static PyObject *
+_asyncio__get_event_loop_impl(PyObject *module, int stacklevel);
+
+static PyObject *
+_asyncio__get_event_loop(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject *kwnames)
+{
+    PyObject *return_value = NULL;
+    static const char * const _keywords[] = {"stacklevel", NULL};
+    static _PyArg_Parser _parser = {NULL, _keywords, "_get_event_loop", 0};
+    PyObject *argsbuf[1];
+    Py_ssize_t noptargs = nargs + (kwnames ? PyTuple_GET_SIZE(kwnames) : 0) - 0;
+    int stacklevel = 3;
+
+    args = _PyArg_UnpackKeywords(args, nargs, NULL, kwnames, &_parser, 0, 1, 0, argsbuf);
+    if (!args) {
+        goto exit;
+    }
+    if (!noptargs) {
+        goto skip_optional_pos;
+    }
+    stacklevel = _PyLong_AsInt(args[0]);
+    if (stacklevel == -1 && PyErr_Occurred()) {
+        goto exit;
+    }
+skip_optional_pos:
+    return_value = _asyncio__get_event_loop_impl(module, stacklevel);
+
+exit:
+    return return_value;
+}
+
 PyDoc_STRVAR(_asyncio_get_running_loop__doc__,
 "get_running_loop($module, /)\n"
 "--\n"
@@ -832,4 +871,4 @@ _asyncio__leave_task(PyObject *module, PyObject *const *args, Py_ssize_t nargs,
 exit:
     return return_value;
 }
-/*[clinic end generated code: output=d0fc522bcbff9d61 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=0d127162ac92e0c0 input=a9049054013a1b77]*/