gh-156988: Fix asyncio call graph breaking at sync generators (#156991)

Author: deadlovelll

Lib/asyncio/graph.py

@@ -155,7 +155,9 @@ def capture_call_graph(
     f = sys._getframe(depth) if limit != 0 else None
     try:
         while f is not None:
-            is_async = f.f_generator is not None
+            # gh-156988: sync gen should not clear the call chain
+            is_async = isinstance(
+                f.f_generator, (types.CoroutineType, types.AsyncGeneratorType))
             call_stack.append(FrameCallGraphEntry(f))
 
             if is_async:

Lib/test/test_asyncio/test_graph.py

@@ -593,6 +593,26 @@ async def main():
         await main()
         self.assertRegex(output[0], r'in generator [\w.<>]+\.gen\(\)')
 
+    async def test_capture_call_graph_generator_keeps_caller_frames(self):
+        # gh-156988: sync gen should not clear the call chain
+        stack = None
+
+        def gen():
+            nonlocal stack
+            graph = asyncio.capture_call_graph()
+            stack = [entry.frame.f_code.co_name for entry in graph.call_stack]
+            yield
+
+        def middle():
+            for _ in gen():
+                pass
+
+        async def main():
+            middle()
+
+        await main()
+        self.assertEqual(stack[:3], ['gen', 'middle', 'main'])
+
 
 @unittest.skipIf(
     not hasattr(asyncio.futures, "_c_future_add_to_awaited_by"),

Misc/NEWS.d/next/Library/2026-09-05-18-23-30.gh-issue-156988.nEUQE6.rst

@@ -0,0 +1,2 @@
+:func:`asyncio.print_call_graph` no longer truncates the call stack at a
+synchronous generator.