From 1b70914513792ffc9e57dc5b0bb682ccda46e802 Mon Sep 17 00:00:00 2001
From: Timofei Ivankov <128279579+deadlovelll@users.noreply.github.com>
Date: Sat, 29 Aug 2026 13:04:57 +0300
Subject: [PATCH] [3.14] gh-156408: Fix asyncio.print_call_graph() on a
 finished task (GH-156410) (cherry picked from commit
 6c425f1d18d3915cb32e3372647db24bad7ab92d)

Co-authored-by: Timofei Ivankov <128279579+deadlovelll@users.noreply.github.com>
---
 Lib/asyncio/graph.py                           |  3 ++-
 Lib/test/test_asyncio/test_graph.py            | 18 ++++++++++++++++++
 ...6-08-26-12-48-10.gh-issue-156408.-Yd0k7.rst |  2 ++
 3 files changed, 22 insertions(+), 1 deletion(-)
 create mode 100644 Misc/NEWS.d/next/Library/2026-08-26-12-48-10.gh-issue-156408.-Yd0k7.rst

diff --git a/Lib/asyncio/graph.py b/Lib/asyncio/graph.py
index 35f7fa62140bd4..54df7afa5553b9 100644
--- a/Lib/asyncio/graph.py
+++ b/Lib/asyncio/graph.py
@@ -58,7 +58,8 @@ def _build_graph_for_future(
     while coro is not None:
         if hasattr(coro, 'cr_await'):
             # A native coroutine or duck-type compatible iterator
-            st.append(FrameCallGraphEntry(coro.cr_frame))
+            if coro.cr_frame is not None:
+                st.append(FrameCallGraphEntry(coro.cr_frame))
             coro = coro.cr_await
         elif hasattr(coro, 'ag_await'):
             # A native async generator or duck-type compatible iterator
diff --git a/Lib/test/test_asyncio/test_graph.py b/Lib/test/test_asyncio/test_graph.py
index 2f22fbccba42bc..46a7c3d3192837 100644
--- a/Lib/test/test_asyncio/test_graph.py
+++ b/Lib/test/test_asyncio/test_graph.py
@@ -345,6 +345,24 @@ async def main():
 
         self.assertTrue(stack_for_fut[1].startswith('* Future(id='))
 
+    async def test_call_graph_finished_task(self):
+        # gh-156408: the call graph must not record a finished coroutine's None frame
+        async def boom():
+            raise ValueError
+
+        done = asyncio.create_task(asyncio.sleep(0), name='done')
+        failed = asyncio.create_task(boom(), name='failed')
+        cancelled = asyncio.create_task(asyncio.Event().wait(), name='cancelled')
+        cancelled.cancel()
+        await asyncio.gather(done, failed, cancelled, return_exceptions=True)
+
+        for task in (done, failed, cancelled):
+            with self.subTest(task=task.get_name()):
+                buf = io.StringIO()
+                asyncio.print_call_graph(task, file=buf)
+                self.assertEqual(asyncio.capture_call_graph(task).call_stack, ())
+                self.assertIn(f"name={task.get_name()!r}", buf.getvalue())
+
 
 @unittest.skipIf(
     not hasattr(asyncio.futures, "_c_future_add_to_awaited_by"),
diff --git a/Misc/NEWS.d/next/Library/2026-08-26-12-48-10.gh-issue-156408.-Yd0k7.rst b/Misc/NEWS.d/next/Library/2026-08-26-12-48-10.gh-issue-156408.-Yd0k7.rst
new file mode 100644
index 00000000000000..62c92838b5c126
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-08-26-12-48-10.gh-issue-156408.-Yd0k7.rst
@@ -0,0 +1,2 @@
+Fix :func:`asyncio.print_call_graph` raising :exc:`AttributeError` when
+called on a task that has already finished.