Perform unfolding of headers when parsing message (#71)

* ✅ [#70] Test newlines not being added to subject

* ✨ [#70] Add the email.policy.EmailPolicy

https://docs.python.org/3/library/email.policy.html#email.policy.EmailPolicy
This results in the unfolding of headers that have previously been
folded, so that new lines don't cause errors.

django_yubin/models.py

@@ -1,5 +1,7 @@
 import datetime
 import logging
+import email
+from email import policy
 from email import encoders as Encoders
 from email.mime.base import MIMEBase
 
@@ -15,7 +17,7 @@
 from django.utils.text import Truncator
 from django.utils.timezone import now
 from django.utils.translation import gettext_lazy as _
-import mailparser
+from mailparser import MailParser
 
 from . import mailparser_utils, tasks
 
@@ -131,7 +133,8 @@ def recipients(self):
         return self.to() + self.cc() + self.bcc()
 
     def get_message_parser(self):
-        return mailparser.parse_from_string(self.message_data)
+        message = email.message_from_string(self.message_data, policy=policy.default)
+        return MailParser(message)
 
     def get_email_message(self):
         """

tests/tests/test_models.py

@@ -3,7 +3,7 @@
 from email.generator import _fmt
 from unittest.mock import patch
 
-from django.core.mail import EmailMultiAlternatives
+from django.core.mail import EmailMessage, EmailMultiAlternatives
 from django.test import TestCase
 from django.utils import timezone
 
@@ -200,3 +200,26 @@ def reset_mock():
         with self.subTest("compare message as_string"):
             self.assertEqual(reconstructed_msg.as_string(), ref_as_string)
             reset_mock()
+
+    def test_email_with_long_subject(self):
+        email_message = EmailMessage(
+        "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor "
+        "incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco "
+        "laboris nisi ut aliquip ex ea commodo consequat.",
+        "Message body",
+        '[email protected]',
+        ['[email protected]']
+        )
+
+        message = Message.objects.create(
+            to_address=','.join(email_message.to),
+            cc_address=','.join(email_message.cc),
+            bcc_address=','.join(email_message.bcc),
+            from_address=email_message.from_email,
+            subject=email_message.subject,
+            message_data=email_message.message().as_string(),
+        )
+
+        parsed_message = message.get_email_message()
+
+        self.assertNotIn("\n", parsed_message.subject)