[2.2.x] Fixed #30523 -- Fixed updating file modification times on seen files in auto-reloader when using StatReloader.

Previously we updated the file mtimes if the file has not been seen
before - i.e on the first iteration of the loop.

If the mtime has been changed we triggered the notify_file_changed()
method which in all cases except the translations will result in the
process being terminated. To be strictly correct we need to update the
mtime for either branch of the conditional.

Regression in 6754bffa2b.

Backport of 480492fe70 from master

django/utils/autoreload.py

@@ -333,9 +333,9 @@ class StatReloader(BaseReloader):
         while True:
             for filepath, mtime in self.snapshot_files():
                 old_time = mtimes.get(filepath)
+                mtimes[filepath] = mtime
                 if old_time is None:
                     logger.debug('File %s first seen with mtime %s', filepath, mtime)
-                    mtimes[filepath] = mtime
                     continue
                 elif mtime > old_time:
                     logger.debug('File %s previous mtime: %s, current mtime: %s', filepath, old_time, mtime)

docs/releases/2.2.2.txt

@@ -28,3 +28,7 @@ Bugfixes
 
 * Fixed a regression in Django 2.2 that caused a crash of auto-reloader when
   an exception with custom signature is raised (:ticket:`30516`).
+
+* Fixed a regression in Django 2.2.1 where auto-reloader unnecessarily reloads
+  translation files multiple times when using ``StatReloader``
+  (:ticket:`30523`).

tests/utils_tests/test_autoreload.py

@@ -656,6 +656,16 @@ class StatReloaderTests(ReloaderTests, IntegrationTests):
         # Shorten the sleep time to speed up tests.
         self.reloader.SLEEP_TIME = 0.01
 
+    @mock.patch('django.utils.autoreload.StatReloader.notify_file_changed')
+    def test_tick_does_not_trigger_twice(self, mock_notify_file_changed):
+        with mock.patch.object(self.reloader, 'watched_files', return_value=[self.existing_file]):
+            ticker = self.reloader.tick()
+            next(ticker)
+            self.increment_mtime(self.existing_file)
+            next(ticker)
+            next(ticker)
+            self.assertEqual(mock_notify_file_changed.call_count, 1)
+
     def test_snapshot_files_ignores_missing_files(self):
         with mock.patch.object(self.reloader, 'watched_files', return_value=[self.nonexistent_file]):
             self.assertEqual(dict(self.reloader.snapshot_files()), {})