Connection object is no passed to the EmailMessage constructor when called from send_mass_mail

[Fedor Tyurin]

There is a difference in the behavior of send_mail and send_mass_mail function. send_mail passes connection as a parameter to the EmailMessage constructor and send_mass_mail does not.

44	def send_mail(subject, message, from_email, recipient_list,
45	              fail_silently=False, auth_user=None, auth_password=None,
46	              connection=None):
...
57	    connection = connection or get_connection(username=auth_user,
58	                                    password=auth_password,
59	                                    fail_silently=fail_silently)
60	    return EmailMessage(subject, message, from_email, recipient_list,
61	                        connection=connection).send()

64	def send_mass_mail(datatuple, fail_silently=False, auth_user=None,
65	                   auth_password=None, connection=None):
...
78	    connection = connection or get_connection(username=auth_user,
79	                                    password=auth_password,
80	                                    fail_silently=fail_silently)
81	    messages = [EmailMessage(subject, message, sender, recipient)
82	                for subject, message, sender, recipient in datatuple]
83	    return connection.send_messages(messages)

This causes troubles if email backend stores something inside the self object for the later use and expects that messages would have reference to it.

[Jannis Leidel]

LGTM (for the record, please don't mark ticket as RFC if you're the ticket author :)

[Claude Paroz]

In [17827]:

Fixed #17811 -- Added connection parameter in call to EmailMessage from send_mass_mail. Thanks fed239 for the report and danielr for the patch.

[Mike Edmunds]

Replying to Fedor Tyurin:

This causes troubles if email backend stores something inside the self object for the later use and expects that messages would have reference to it.

In general, an EmailBackend instance cannot assume that EmailMessage.connection has been set to the backend instance after the backend has been used to send the message. Django supports (and ​documents) directly calling backend.send_messages([... list of EmailMessage ...]), which doesn't set the connection property on the sent messages. See #35864.

If a specific backend implementation needs to ensure EmailMessage.connection is always set, it should set each message's connection property to self in its send_messages() method.

(Also, we're about to deprecate and remove connection entirely as part of #35514.)