gh-125512: Revert "gh-124872: Replace enter/exit events with "switched" (#124776)" (#125513)

1 files changed, 38 insertions, 41 deletions

diff --git a/Modules/_testcapi/watchers.c b/Modules/_testcapi/watchers.c
index 321d3ae..b4233d0 100644
--- a/Modules/_testcapi/watchers.c
+++ b/Modules/_testcapi/watchers.c
@@ -626,12 +626,16 @@ allocate_too_many_func_watchers(PyObject *self, PyObject *args)
 // Test contexct object watchers
 #define NUM_CONTEXT_WATCHERS 2
 static int context_watcher_ids[NUM_CONTEXT_WATCHERS] = {-1, -1};
-static PyObject *context_switches[NUM_CONTEXT_WATCHERS];
+static int num_context_object_enter_events[NUM_CONTEXT_WATCHERS] = {0, 0};
+static int num_context_object_exit_events[NUM_CONTEXT_WATCHERS] = {0, 0};
 
 static int
 handle_context_watcher_event(int which_watcher, PyContextEvent event, PyObject *ctx) {
-    if (event == Py_CONTEXT_SWITCHED) {
-        PyList_Append(context_switches[which_watcher], ctx);
+    if (event == Py_CONTEXT_EVENT_ENTER) {
+        num_context_object_enter_events[which_watcher]++;
+    }
+    else if (event == Py_CONTEXT_EVENT_EXIT)  {
+        num_context_object_exit_events[which_watcher]++;
     }
     else {
         return -1;
@@ -663,28 +667,31 @@ error_context_event_handler(PyContextEvent event, PyObject *ctx) {
 static PyObject *
 add_context_watcher(PyObject *self, PyObject *which_watcher)
 {
-    static const PyContext_WatchCallback callbacks[] = {
-        &first_context_watcher_callback,
-        &second_context_watcher_callback,
-        &error_context_event_handler,
-    };
+    int watcher_id;
     assert(PyLong_Check(which_watcher));
     long which_l = PyLong_AsLong(which_watcher);
-    if (which_l < 0 || which_l >= (long)Py_ARRAY_LENGTH(callbacks)) {
+    if (which_l == 0) {
+        watcher_id = PyContext_AddWatcher(first_context_watcher_callback);
+        context_watcher_ids[0] = watcher_id;
+        num_context_object_enter_events[0] = 0;
+        num_context_object_exit_events[0] = 0;
+    }
+    else if (which_l == 1) {
+        watcher_id = PyContext_AddWatcher(second_context_watcher_callback);
+        context_watcher_ids[1] = watcher_id;
+        num_context_object_enter_events[1] = 0;
+        num_context_object_exit_events[1] = 0;
+    }
+    else if (which_l == 2) {
+        watcher_id = PyContext_AddWatcher(error_context_event_handler);
+    }
+    else {
         PyErr_Format(PyExc_ValueError, "invalid watcher %d", which_l);
         return NULL;
     }
-    int watcher_id = PyContext_AddWatcher(callbacks[which_l]);
     if (watcher_id < 0) {
         return NULL;
     }
-    if (which_l >= 0 && which_l < NUM_CONTEXT_WATCHERS) {
-        context_watcher_ids[which_l] = watcher_id;
-        Py_XSETREF(context_switches[which_l], PyList_New(0));
-        if (context_switches[which_l] == NULL) {
-            return NULL;
-        }
-    }
     return PyLong_FromLong(watcher_id);
 }
 
@@ -701,7 +708,8 @@ clear_context_watcher(PyObject *self, PyObject *watcher_id)
         for (int i = 0; i < NUM_CONTEXT_WATCHERS; i++) {
             if (watcher_id_l == context_watcher_ids[i]) {
                 context_watcher_ids[i] = -1;
-                Py_CLEAR(context_switches[i]);
+                num_context_object_enter_events[i] = 0;
+                num_context_object_exit_events[i] = 0;
             }
         }
     }
@@ -709,34 +717,21 @@ clear_context_watcher(PyObject *self, PyObject *watcher_id)
 }
 
 static PyObject *
-clear_context_stack(PyObject *Py_UNUSED(self), PyObject *Py_UNUSED(args))
+get_context_watcher_num_enter_events(PyObject *self, PyObject *watcher_id)
 {
-    PyThreadState *tstate = PyThreadState_Get();
-    if (tstate->context == NULL) {
-        Py_RETURN_NONE;
-    }
-    if (((PyContext *)tstate->context)->ctx_prev != NULL) {
-        PyErr_SetString(PyExc_RuntimeError,
-                        "must first exit all non-base contexts");
-        return NULL;
-    }
-    Py_CLEAR(tstate->context);
-    Py_RETURN_NONE;
+    assert(PyLong_Check(watcher_id));
+    long watcher_id_l = PyLong_AsLong(watcher_id);
+    assert(watcher_id_l >= 0 && watcher_id_l < NUM_CONTEXT_WATCHERS);
+    return PyLong_FromLong(num_context_object_enter_events[watcher_id_l]);
 }
 
 static PyObject *
-get_context_switches(PyObject *Py_UNUSED(self), PyObject *watcher_id)
+get_context_watcher_num_exit_events(PyObject *self, PyObject *watcher_id)
 {
     assert(PyLong_Check(watcher_id));
     long watcher_id_l = PyLong_AsLong(watcher_id);
-    if (watcher_id_l < 0 || watcher_id_l >= NUM_CONTEXT_WATCHERS) {
-        PyErr_Format(PyExc_ValueError, "invalid watcher %ld", watcher_id_l);
-        return NULL;
-    }
-    if (context_switches[watcher_id_l] == NULL) {
-        return PyList_New(0);
-    }
-    return Py_NewRef(context_switches[watcher_id_l]);
+    assert(watcher_id_l >= 0 && watcher_id_l < NUM_CONTEXT_WATCHERS);
+    return PyLong_FromLong(num_context_object_exit_events[watcher_id_l]);
 }
 
 static PyObject *
@@ -840,8 +835,10 @@ static PyMethodDef test_methods[] = {
     // Code object watchers.
     {"add_context_watcher",         add_context_watcher,        METH_O,       NULL},
     {"clear_context_watcher",       clear_context_watcher,      METH_O,       NULL},
-    {"clear_context_stack",      clear_context_stack,     METH_NOARGS,  NULL},
-    {"get_context_switches",     get_context_switches,    METH_O,       NULL},
+    {"get_context_watcher_num_enter_events",
+     get_context_watcher_num_enter_events,                 METH_O,       NULL},
+    {"get_context_watcher_num_exit_events",
+     get_context_watcher_num_exit_events,               METH_O,       NULL},
     {"allocate_too_many_context_watchers",
      (PyCFunction) allocate_too_many_context_watchers,       METH_NOARGS,  NULL},
     {NULL},