From ce6ef4d3c5be76fca9d63f3d6202f218b73175b3 Mon Sep 17 00:00:00 2001
From: knokko <tim@codeyellow.nl>
Date: Thu, 4 Apr 2024 14:22:45 +0200
Subject: [PATCH] Dont put auto_now and auto_now_add fields in the history

---
 binder/history.py                      | 22 ++++++++++++++++++++--
 tests/test_history.py                  | 20 ++++++++++++++++++++
 tests/testapp/models/contact_person.py |  3 +++
 3 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/binder/history.py b/binder/history.py
index 698f9377..3137cb80 100644
--- a/binder/history.py
+++ b/binder/history.py
@@ -7,6 +7,7 @@
 from django.contrib.auth import get_user_model
 from django.conf import settings
 from django.dispatch import Signal
+from django.core.exceptions import FieldDoesNotExist
 
 from .json import jsondumps, JsonResponse
 
@@ -172,7 +173,18 @@ def _commit():
 	)
 	changeset.save()
 
+	auto_now_counter = 0
+
 	for (model, oid, field), (old, new, diff) in _Transaction.changes.items():
+
+		# Skip auto_now and auto_now_add fields because they are not interesting for the history
+		try:
+			field_properties = model._meta.get_field(field)
+			if field_properties.auto_now or field_properties.auto_now_add:
+				auto_now_counter += 1
+		except (FieldDoesNotExist, AttributeError):
+			pass
+
 		# New instances get None for all the before values
 		if old is NewInstanceField:
 			old = None
@@ -191,8 +203,14 @@ def _commit():
 
 	transaction_commit.send(sender=None, changeset=changeset)
 
-	# Save the changeset again, to update the date to be as close to DB transaction commit start as possible.
-	changeset.save()
+	if changeset.changes.count() > auto_now_counter:
+		# Save the changeset again, to update the date to be as close to DB transaction commit start as possible.
+		changeset.save()
+	else:
+		# Changesets without real changes are useless
+		changeset.changes.all().delete()
+		changeset.delete()
+
 	_Transaction.stop()
 
 
diff --git a/tests/test_history.py b/tests/test_history.py
index 00464d95..a792fed6 100644
--- a/tests/test_history.py
+++ b/tests/test_history.py
@@ -80,7 +80,27 @@ def test_model_with_history_creates_changes_on_creation(self):
 		self.assertEqual(1, Change.objects.filter(changeset=cs, model='Animal', field='deleted', before='null', after='false').count())
 		self.assertEqual(1, Change.objects.filter(changeset=cs, model='Animal', field='birth_date', before='null', after='null').count())
 
+	def test_do_not_keep_auto_now_only_changesets(self):
+		tim = ContactPerson.objects.create(name="Tim")
 
+		self.assertEqual(0, Changeset.objects.count())
+		self.assertEqual(0, Change.objects.count())
+
+		self.assertEqual(self.client.patch(
+			'/contact_person/%d/' % tim.pk, data=json.dumps({'name': 'Tim'}), content_type='application/json'
+		).status_code, 200)
+
+		self.assertEqual(0, Change.objects.count())
+		self.assertEqual(0, Changeset.objects.count())
+
+		self.assertEqual(self.client.patch(
+			'/contact_person/%d/' % tim.pk, data=json.dumps({'name': 'knokko'}), content_type='application/json'
+		).status_code, 200)
+
+		self.assertEqual(2, Change.objects.count())
+		self.assertEqual(1, Changeset.objects.count())
+		self.assertEqual(1, Change.objects.filter(model='ContactPerson', after='"knokko"').count())
+		self.assertEqual(1, Change.objects.filter(model='ContactPerson', field='updated_at').count())
 
 	def test_model_with_history_creates_changes_on_update_but_only_for_changed_fields(self):
 		daffy = Animal(name='Daffy Duck')
diff --git a/tests/testapp/models/contact_person.py b/tests/testapp/models/contact_person.py
index 60db9897..241ee971 100644
--- a/tests/testapp/models/contact_person.py
+++ b/tests/testapp/models/contact_person.py
@@ -7,6 +7,9 @@ class ContactPerson(BinderModel):
 	created_at = models.DateTimeField(auto_now_add=True)
 	updated_at = models.DateTimeField(auto_now=True)
 
+	class Binder:
+		history = True
+
 	def __str__(self):
 		return 'contact_person %d: %s' % (self.pk, self.name)