GH-92236: Remove spurious "line" event when starting coroutine or generator. (GH-92722) (GH-92772)

(cherry picked from commit 22a1db378c5c381272362c5b2f68ac78a368e136)

1 files changed, 53 insertions, 0 deletions

diff --git a/Lib/test/test_sys_settrace.py b/Lib/test/test_sys_settrace.py
index b1c8f6f..1a67fa6 100644
--- a/Lib/test/test_sys_settrace.py
+++ b/Lib/test/test_sys_settrace.py
@@ -7,6 +7,7 @@ import difflib
 import gc
 from functools import wraps
 import asyncio
+from test.support import import_helper
 
 support.requires_working_socket(module=True)
 
@@ -1473,6 +1474,58 @@ class TraceTestCase(unittest.TestCase):
              (3, 'return'),
              (1, 'return')])
 
+    @support.cpython_only
+    def test_no_line_event_after_creating_generator(self):
+        # Spurious line events before call events only show up with C tracer
+
+        # Skip this test if the _testcapi module isn't available.
+        _testcapi = import_helper.import_module('_testcapi')
+
+        def gen():
+            yield 1
+
+        def func():
+            for _ in (
+                gen()
+            ):
+                pass
+
+        EXPECTED_EVENTS = [
+            (0, 'call'),
+            (2, 'line'),
+            (1, 'line'),
+            (-3, 'call'),
+            (-2, 'line'),
+            (-2, 'return'),
+            (4, 'line'),
+            (1, 'line'),
+            (-2, 'call'),
+            (-2, 'return'),
+            (1, 'return'),
+        ]
+
+        # C level events should be the same as expected and the same as Python level.
+
+        events = []
+        # Turning on and off tracing must be on same line to avoid unwanted LINE events.
+        _testcapi.settrace_to_record(events); func(); sys.settrace(None)
+        start_line = func.__code__.co_firstlineno
+        events = [
+            (line-start_line, EVENT_NAMES[what])
+            for (what, line, arg) in events
+        ]
+        self.assertEqual(events, EXPECTED_EVENTS)
+
+        self.run_and_compare(func, EXPECTED_EVENTS)
+
+
+EVENT_NAMES = [
+    'call',
+    'exception',
+    'line',
+    'return'
+]
+
 
 class SkipLineEventsTraceTestCase(TraceTestCase):
     """Repeat the trace tests, but with per-line events skipped"""