Preserve last_modified and etag fields after reloading GTFS Feeds

trainvel/gtfs/apps.py

@@ -1,4 +1,5 @@
 from django.apps import AppConfig
+from django.db.models.signals import pre_save
 from django.utils.translation import gettext_lazy as _
 
 
@@ -6,3 +7,8 @@ class TrainvelGTFSConfig(AppConfig):
     default_auto_field = "django.db.models.BigAutoField"
     name = "trainvel.gtfs"
     verbose_name = _("Trainvel - GTFS")
+
+    def ready(self):
+        from trainvel.gtfs import signals
+
+        pre_save.connect(signals.keep_gtfs_feed_modification_date, sender="gtfs.GTFSFeed")

trainvel/gtfs/signals.py

@@ -0,0 +1,14 @@
+from trainvel.gtfs.models import GTFSFeed
+
+
+def keep_gtfs_feed_modification_date(instance: GTFSFeed, raw: bool = True, **_kwargs):
+    """
+    Keep the last_modified and etag fields from the existing GTFSFeed instance when saving a new one.
+    """
+    if raw and GTFSFeed.objects.filter(pk=instance.pk).exists():
+        # If a GTFSFeed instance is being saved from a raw query,
+        # we want to keep the last_modified and etag fields from the existing instance.
+        # This is useful when loading initial data from a fixture, for example.
+        old_instance = GTFSFeed.objects.get(pk=instance.pk)
+        instance.last_modified = old_instance.last_modified
+        instance.etag = old_instance.etag