pythongh-90535: Warn of deprecation of intervals other than 1 with when='MIDNIGHT'.

Author: vsajip

Lib/logging/handlers.py

@@ -28,6 +28,7 @@
 import queue
 import threading
 import copy
+import warnings
 
 #
 # Some constants...
@@ -258,6 +259,11 @@ def __init__(self, filename, when='h', interval=1, backupCount=0,
             raise ValueError("Invalid rollover interval specified: %s" % self.when)
 
         self.extMatch = re.compile(self.extMatch, re.ASCII)
+        if self.when == 'MIDNIGHT' and interval != 1:
+            msg = (f'An interval of {interval} is incompatible with '
+                   "when='MIDNIGHT'. Use when='D' (for days) "
+                   'if you want to use an interval other than 1.')
+            warnings.warn(msg, category=DeprecationWarning, stacklevel=2)
         self.interval = self.interval * interval # multiply by units requested
         # The following line added because the filename passed in could be a
         # path object (see Issue #27493), but self.baseFilename will be a string

Lib/test/test_logging.py

@@ -5755,6 +5755,16 @@ def test_compute_rollover_daily_attime(self):
         finally:
             rh.close()
 
+    def test_midnight_interval(self):
+        with warnings.catch_warnings(record=True) as w:
+            rh = logging.handlers.TimedRotatingFileHandler(
+                self.fn, encoding="utf-8", when='MIDNIGHT', interval=2, backupCount=0,
+                utc=True)
+            rh.close()
+        if w:
+            self.assertIs(w[0].category, DeprecationWarning)
+            self.assertIn('An interval of 2 is incompatible ', str(w[0].message))
+
     #@unittest.skipIf(True, 'Temporarily skipped while failures investigated.')
     def test_compute_rollover_weekly_attime(self):
         currentTime = int(time.time())