From 94194e0f5eeacf1be2a88a28bfed62dbc6c5d5a2 Mon Sep 17 00:00:00 2001
From: Daniel Garcia Moreno <daniel.garcia@suse.com>
Date: Thu, 6 Oct 2022 12:53:56 +0200
Subject: [PATCH] Fix django4.1 compatibility issues with related fields

In Django4.1 a ValueError exception is raised when trying to access to
foreign keys for unsaved model instances:

https://docs.djangoproject.com/en/4.1/releases/4.1/#reverse-foreign-key-changes-for-unsaved-model-instances

This patch ensures that everything is saved before trying to use related
models and handles the exception correctly in the Thread model pre_save.
---
 hyperkitty/models/thread.py           | 8 ++++++++
 hyperkitty/tests/models/test_email.py | 6 ++++++
 2 files changed, 14 insertions(+)

diff --git a/hyperkitty/models/thread.py b/hyperkitty/models/thread.py
index b550cdb8..e49954a7 100644
--- a/hyperkitty/models/thread.py
+++ b/hyperkitty/models/thread.py
@@ -148,10 +148,18 @@ class Thread(models.Model):
         from .email import Email  # circular import
         if self.starting_email is not None:
             return
+
         try:
             self.starting_email = self.emails.get(parent_id__isnull=True)
         except Email.DoesNotExist:
             self.starting_email = self.emails.order_by("date").first()
+        except ValueError:
+            # If the Thread is not created yet, the self.emails will raise a
+            # ValueError exception. This happens at creation time because this
+            # method is called by on_pre_save
+            #
+            # https://docs.djangoproject.com/en/4.1/releases/4.1/#reverse-foreign-key-changes-for-unsaved-model-instances
+            return
 
     def on_pre_save(self):
         self.find_starting_email()
diff --git a/hyperkitty/tests/models/test_email.py b/hyperkitty/tests/models/test_email.py
index 7bcac390..f194e2b1 100644
--- a/hyperkitty/tests/models/test_email.py
+++ b/hyperkitty/tests/models/test_email.py
@@ -195,6 +195,9 @@ class EmailTestCase(TestCase):
                       subject="This is a folded\n subject",
                       in_reply_to="<msg1.example.com>\n <msg2.example.com>",
                       content="Dummy message")
+        sender.save()
+        mlist.save()
+        email.save()
         msg = email.as_message()
         self.assertEqual(msg["Subject"], "This is a folded subject")
 
@@ -210,6 +213,9 @@ class EmailTestCase(TestCase):
                       mailinglist=mlist,
                       subject="Message subject",
                       content="Dummy message")
+        sender.save()
+        mlist.save()
+        email.save()
         msg = email.as_message()
         self.assertEqual(msg['from'], '"Team: J.Q. Doe" <dummy@example.com>')
 
-- 
2.37.3