Refs #35581 -- Used modern email parser and helpers in mail tests.

- Used modern email API (policy.default) for tests that reparse
  generated messages, and switched to modern accessors where helpful.
- Split get_raw_attachments() helper out of get_decoded_attachments(),
  and used modern iter_attachments() to avoid finding nested attachments
  in attached message/* emails.
- Stopped using legacy parseaddr.

tests/mail/tests.py

@@ -4,10 +4,10 @@ import shutil
 import socket
 import sys
 import tempfile
-from email import charset, message_from_binary_file, message_from_bytes
+from email import charset, message_from_binary_file
-from email.header import Header
+from email import message_from_bytes as _message_from_bytes
+from email import policy
 from email.mime.text import MIMEText
-from email.utils import parseaddr
 from io import StringIO
 from pathlib import Path
 from smtplib import SMTP, SMTPException
@@ -41,6 +41,14 @@ except ImportError:
     HAS_AIOSMTPD = False
 
 
+def message_from_bytes(s):
+    """
+    email.message_from_bytes() using modern email.policy.default.
+    Returns a modern email.message.EmailMessage.
+    """
+    return _message_from_bytes(s, policy=policy.default)
+
+
 class MailTestsMixin:
     def assertMessageHasHeaders(self, message, headers):
         """
@@ -101,24 +109,35 @@ class MailTestsMixin:
                 "First string doesn't end with the second.",
             )
 
-    def get_decoded_attachments(self, django_message):
+    def get_raw_attachments(self, django_message):
         """
-        Encode the specified django.core.mail.message.EmailMessage, then decode
+        Return a list of the raw attachment parts in the MIME message generated
-        it using Python's email.parser module and, for each attachment of the
+        by serializing django_message and reparsing the result.
-        message, return a list of tuples with (filename, content, mimetype).
+
+        This returns only "top-level" attachments. It will not descend into
+        message/* attached emails to find nested attachments.
         """
         msg_bytes = django_message.message().as_bytes()
-        email_message = message_from_bytes(msg_bytes)
+        message = message_from_bytes(msg_bytes)
+        return list(message.iter_attachments())
 
-        def iter_attachments():
+    def get_decoded_attachments(self, django_message):
-            for i in email_message.walk():
+        """
-                if i.get_content_disposition() == "attachment":
+        Return a list of decoded attachments resulting from serializing
-                    filename = i.get_filename()
+        django_message and reparsing the result.
-                    content = i.get_payload(decode=True)
-                    mimetype = i.get_content_type()
-                    yield filename, content, mimetype
 
-        return list(iter_attachments())
+        Each attachment is returned as an EmailAttachment named tuple with
+        fields filename, content, and mimetype. The content will be decoded
+        to str for mimetype text/*; retained as bytes for other mimetypes.
+        """
+        return [
+            EmailAttachment(
+                attachment.get_filename(),
+                attachment.get_content(),
+                attachment.get_content_type(),
+            )
+            for attachment in self.get_raw_attachments(django_message)
+        ]
 
 
 class MailTests(MailTestsMixin, SimpleTestCase):
@@ -684,7 +703,7 @@ class MailTests(MailTestsMixin, SimpleTestCase):
         self.assertEqual(msg.attachments[0].mimetype, mime_type)
 
         attachments = self.get_decoded_attachments(msg)
-        self.assertEqual(attachments[0], (file_name, file_content.encode(), mime_type))
+        self.assertEqual(attachments[0], (file_name, file_content, mime_type))
 
     def test_attachments_constructor(self):
         file_name = "example.txt"
@@ -706,7 +725,7 @@ class MailTests(MailTestsMixin, SimpleTestCase):
         self.assertEqual(msg.attachments[0].mimetype, mime_type)
 
         attachments = self.get_decoded_attachments(msg)
-        self.assertEqual(attachments[0], (file_name, file_content.encode(), mime_type))
+        self.assertEqual(attachments[0], (file_name, file_content, mime_type))
 
     def test_attachments_constructor_from_tuple(self):
         file_name = "example.txt"
@@ -726,7 +745,7 @@ class MailTests(MailTestsMixin, SimpleTestCase):
         self.assertEqual(msg.attachments[0].mimetype, mime_type)
 
         attachments = self.get_decoded_attachments(msg)
-        self.assertEqual(attachments[0], (file_name, file_content.encode(), mime_type))
+        self.assertEqual(attachments[0], (file_name, file_content, mime_type))
 
     def test_attachments_constructor_omit_mimetype(self):
         """
@@ -767,10 +786,8 @@ class MailTests(MailTestsMixin, SimpleTestCase):
         msg = EmailMessage(body="Content")
         # Unicode in file name
         msg.attach("une pièce jointe.pdf", b"%PDF-1.4.%...", mimetype="application/pdf")
-        msg_bytes = msg.message().as_bytes()
+        attachment = self.get_decoded_attachments(msg)[0]
-        message = message_from_bytes(msg_bytes)
+        self.assertEqual(attachment.filename, "une pièce jointe.pdf")
-        payload = message.get_payload()
-        self.assertEqual(payload[1].get_filename(), "une pièce jointe.pdf")
 
     def test_attach_file(self):
         """
@@ -830,7 +847,7 @@ class MailTests(MailTestsMixin, SimpleTestCase):
         msg.attach("file.txt", b"file content")
         filename, content, mimetype = self.get_decoded_attachments(msg)[0]
         self.assertEqual(filename, "file.txt")
-        self.assertEqual(content, b"file content")
+        self.assertEqual(content, "file content")  # (decoded)
         self.assertEqual(mimetype, "text/plain")
 
     def test_attach_utf8_text_as_bytes(self):
@@ -842,7 +859,7 @@ class MailTests(MailTestsMixin, SimpleTestCase):
         msg.attach("file.txt", b"\xc3\xa4")  # UTF-8 encoded a umlaut.
         filename, content, mimetype = self.get_decoded_attachments(msg)[0]
         self.assertEqual(filename, "file.txt")
-        self.assertEqual(content, b"\xc3\xa4")
+        self.assertEqual(content, "ä")  # (decoded)
         self.assertEqual(mimetype, "text/plain")
 
     def test_attach_non_utf8_text_as_bytes(self):
@@ -1341,10 +1358,9 @@ class BaseEmailBackendTests(MailTestsMixin):
         num_sent = mail.get_connection().send_messages([email])
         self.assertEqual(num_sent, 1)
         message = self.get_the_message()
-        self.assertEqual(message["subject"], "=?utf-8?q?Ch=C3=A8re_maman?=")
+        self.assertEqual(message["subject"], "Chère maman")
-        self.assertEqual(
+        self.assertIn(b"Subject: =?utf-8?q?Ch=C3=A8re_maman?=", message.as_bytes())
-            message.get_payload(decode=True).decode(), "Je t'aime très fort"
+        self.assertEqual(message.get_content(), "Je t'aime très fort")
-        )
 
     def test_send_long_lines(self):
         """
@@ -1390,8 +1406,10 @@ class BaseEmailBackendTests(MailTestsMixin):
         )
         email.send()
         message = self.get_the_message()
-        self.assertEqual(
+        self.assertEqual(message["from"], "Firstname Sürname <from@example.com>")
-            message["from"], "=?utf-8?q?Firstname_S=C3=BCrname?= <from@example.com>"
+        self.assertIn(
+            b"From: =?utf-8?q?Firstname_S=C3=BCrname?= <from@example.com>",
+            message.as_bytes(),
         )
 
     def test_plaintext_send_mail(self):
@@ -1623,7 +1641,10 @@ class LocmemBackendTests(BaseEmailBackendTests, SimpleTestCase):
     email_backend = "django.core.mail.backends.locmem.EmailBackend"
 
     def get_mailbox_content(self):
-        return [m.message() for m in mail.outbox]
+        # Reparse as modern messages to work with shared BaseEmailBackendTests.
+        # (Once EmailMessage.message() uses Python's modern email API, this
+        # can be changed back to `[m.message() for m in mail.outbox]`.)
+        return [message_from_bytes(m.message().as_bytes()) for m in mail.outbox]
 
     def flush_mailbox(self):
         mail.outbox = []
@@ -1702,7 +1723,7 @@ class FileBackendTests(BaseEmailBackendTests, SimpleTestCase):
 
         self.assertEqual(len(os.listdir(self.tmp_dir)), 1)
         with open(os.path.join(self.tmp_dir, os.listdir(self.tmp_dir)[0]), "rb") as fp:
-            message = message_from_binary_file(fp)
+            message = message_from_binary_file(fp, policy=policy.default)
         self.assertEqual(message.get_content_type(), "text/plain")
         self.assertEqual(message.get("subject"), "Subject")
         self.assertEqual(message.get("from"), "from@example.com")
@@ -1791,17 +1812,13 @@ class SMTPHandler:
         mail_from = envelope.mail_from
 
         message = message_from_bytes(data.rstrip())
-        message_addr = parseaddr(message.get("from"))[1]
+        try:
-        if mail_from != message_addr:
+            header_from = message["from"].addresses[0].addr_spec
-            # According to the spec, mail_from does not necessarily match the
+        except (KeyError, IndexError):
-            # From header - this is the case where the local part isn't
+            header_from = None
-            # encoded, so try to correct that.
-            lp, domain = mail_from.split("@", 1)
-            lp = Header(lp, "utf-8").encode()
-            mail_from = "@".join([lp, domain])
 
-        if mail_from != message_addr:
+        if mail_from != header_from:
-            return f"553 '{mail_from}' != '{message_addr}'"
+            return f"553 '{mail_from}' != '{header_from}'"
         self.mailbox.append(message)
         return "250 OK"