[Python-checkins] gh-137200: support frame lineno setter with `BRANCH_LEFT` and `BRANCH_RIGHT` events (GH-137229)

[markshannon]

https://github.com/python/cpython/commit/d18f73ae1349ed005fa05ea2d852e1ab51dbc087
commit: d18f73ae1349ed005fa05ea2d852e1ab51dbc087
branch: main
author: Xuanteng Huang <44627253+xuante...@users.noreply.github.com>
committer: markshannon <m...@hotpy.org>
date: 2025-07-31T14:22:22+01:00
summary:

gh-137200: support frame lineno setter with `BRANCH_LEFT` and `BRANCH_RIGHT` 
events (GH-137229)

files:
M Lib/test/test_monitoring.py
M Objects/frameobject.c

diff --git a/Lib/test/test_monitoring.py b/Lib/test/test_monitoring.py
index a932ac80117d27..4122f786a9afb0 100644
--- a/Lib/test/test_monitoring.py
+++ b/Lib/test/test_monitoring.py
@@ -3,6 +3,7 @@
 import collections
 import dis
 import functools
+import inspect
 import math
 import operator
 import sys
@@ -1709,6 +1710,27 @@ def func(v=1):
             ('branch right', 'func', 6, 8),
             ('branch right', 'func', 2, 10)])
 
+    def test_callback_set_frame_lineno(self):
+        def func(s: str) -> int:
+            if s.startswith("t"):
+                return 1
+            else:
+                return 0
+
+        def callback(code, from_, to):
+            # try set frame.f_lineno
+            frame = inspect.currentframe()
+            while frame and frame.f_code is not code:
+                frame = frame.f_back
+
+            self.assertIsNotNone(frame)
+            frame.f_lineno = frame.f_lineno + 1 # run next instruction
+
+        sys.monitoring.set_local_events(TEST_TOOL, func.__code__, 
E.BRANCH_LEFT)
+        sys.monitoring.register_callback(TEST_TOOL, E.BRANCH_LEFT, callback)
+
+        self.assertEqual(func("true"), 1)
+
 
 class TestBranchConsistency(MonitoringTestBase, unittest.TestCase):
 
diff --git a/Objects/frameobject.c b/Objects/frameobject.c
index 97de1e06efe1b2..72c0ab0666e927 100644
--- a/Objects/frameobject.c
+++ b/Objects/frameobject.c
@@ -1685,6 +1685,8 @@ frame_lineno_set_impl(PyFrameObject *self, PyObject 
*value)
         case PY_MONITORING_EVENT_PY_RESUME:
         case PY_MONITORING_EVENT_JUMP:
         case PY_MONITORING_EVENT_BRANCH:
+        case PY_MONITORING_EVENT_BRANCH_LEFT:
+        case PY_MONITORING_EVENT_BRANCH_RIGHT:
         case PY_MONITORING_EVENT_LINE:
         case PY_MONITORING_EVENT_PY_YIELD:
             /* Setting f_lineno is allowed for the above events */

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