gh-84649: Fix unstable test_rollover_at_midnight (GH-151813)

The test forced a rollover by back-dating the file modification time, but
the rollover time is now based also on the creation time, which cannot be
changed.  Instead, set the rollover time one second after the file
creation time and wait until the clock reaches it.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

diff --git a/Lib/test/test_logging.py b/Lib/test/test_logging.py
index cc2e9b782a3502265080cec7640df7d00c4fdb7e..fcd3da61a078aec3e2dc5e490f6497f8a2e45349 100644 (file)
--- a/Lib/test/test_logging.py
+++ b/Lib/test/test_logging.py
@@ -6705,20 +6705,18 @@ class TimedRotatingFileHandlerTest(BaseFileTest):
 
     def test_rollover_at_midnight(self, weekly=False):
         os_helper.unlink(self.fn)
+        # Emit the first records a little after the beginning of a whole
+        # second, so that their file times fall inside that second and not the
+        # previous one, which would cause an unwanted rollover.
         now = datetime.datetime.now()
-        atTime = now.time()
-        if not 0.1 < atTime.microsecond/1e6 < 0.9:
-            # The test requires all records to be emitted within
-            # the range of the same whole second.
-            time.sleep((0.1 - atTime.microsecond/1e6) % 1.0)
+        if not 0.1 < now.microsecond/1e6 < 0.9:
+            time.sleep((0.1 - now.microsecond/1e6) % 1.0)
             now = datetime.datetime.now()
-            atTime = now.time()
-        atTime = atTime.replace(microsecond=0)
         fmt = logging.Formatter('%(asctime)s %(message)s')
         when = f'W{now.weekday()}' if weekly else 'MIDNIGHT'
         for i in range(3):
             fh = logging.handlers.TimedRotatingFileHandler(
-                self.fn, encoding="utf-8", when=when, atTime=atTime)
+                self.fn, encoding="utf-8", when=when, atTime=now.time())
             fh.setFormatter(fmt)
             r2 = logging.makeLogRecord({'msg': f'testing1 {i}'})
             fh.emit(r2)
@@ -6728,7 +6726,13 @@ class TimedRotatingFileHandlerTest(BaseFileTest):
             for i, line in enumerate(f):
                 self.assertIn(f'testing1 {i}', line)
 
-        os.utime(self.fn, (now.timestamp() - 1,)*2)
+        # The creation time, used to compute the rollover time, cannot be
+        # changed, so the rollover cannot be forced by back-dating the file.
+        # Wait until the clock reaches a rollover time set one second ahead.
+        rollover = int(time.time()) + 1
+        atTime = datetime.datetime.fromtimestamp(rollover).time()
+        while time.time() < rollover:
+            time.sleep(rollover - time.time())
         for i in range(2):
             fh = logging.handlers.TimedRotatingFileHandler(
                 self.fn, encoding="utf-8", when=when, atTime=atTime)
@@ -6736,7 +6740,8 @@ class TimedRotatingFileHandlerTest(BaseFileTest):
             r2 = logging.makeLogRecord({'msg': f'testing2 {i}'})
             fh.emit(r2)
             fh.close()
-        rolloverDate = now - datetime.timedelta(days=7 if weekly else 1)
+        rolloverDate = (datetime.datetime.fromtimestamp(rollover)
+                        - datetime.timedelta(days=7 if weekly else 1))
         otherfn = f'{self.fn}.{rolloverDate:%Y-%m-%d}'
         self.assertLogFile(otherfn)
         with open(self.fn, encoding="utf-8") as f: