django.core.mail.send_mail()'s fail_silently kwarg is documented confusingly

[ティン・ルーフ]

From ​https://docs.djangoproject.com/en/2.0/topics/email/#send-mail: “If it’s False, send_mail will raise an smtplib.SMTPException.”

This is often untrue, and certainly misleading. Certainly, if it's False, send_mail is capable of raising SMTPException, but it's not guaranteed.

I was going to open a pull request and change it to “If it's True, send_mail can raise smtplib.SMTPException”, but I'm not confident that other exceptions cannot be raised, or that send_mail will never raise SMTPException if fail_silently is True.

The main thing I would like would be for the intent of fail_silently to be expressed; what kind of errors is it trying to suppress, for example? What kind of emails could a Django site be sending that are unimportant enough that failing silently is a good idea?

[Sub]

From an initial glance, I can see that fail_silently is only used in the smtp.py service file to decide whether an exception should be raised.

See lines 127-128: ​https://github.com/django/django/blob/5a6f70b4281817656db2f36c5919036d38fcce7f/django/core/mail/backends/smtp.py

The exception to be raised in this case is smtplib.SMTPException. I agree that it does not guarantee that this exception will be raised, and could be misinterpreted. Maybe it would be clearer as "If it’s False, send_mail will raise an smtplib.SMTPException if an error occurs." I think it should definitely be explaining the False case, (not True) as we want to explain the what happens if the failure isn't ignored.

Replying to ティン・ルーフ:

From ​https://docs.djangoproject.com/en/2.0/topics/email/#send-mail: “If it’s False, send_mail will raise an smtplib.SMTPException.”

This is often untrue, and certainly misleading. Certainly, if it's False, send_mail is capable of raising SMTPException, but it's not guaranteed.

I was going to open a pull request and change it to “If it's True, send_mail can raise smtplib.SMTPException”, but I'm not confident that other exceptions cannot be raised, or that send_mail will never raise SMTPException if fail_silently is True.

The main thing I would like would be for the intent of fail_silently to be expressed; what kind of errors is it trying to suppress, for example? What kind of emails could a Django site be sending that are unimportant enough that failing silently is a good idea?

[Tim Graham <timograham@…>]

In 085ebc5f:

Fixed #29430 -- Clarified send_mail()'s fail_silently docs.

[Tim Graham <timograham@…>]

In 84afe81b:

[2.1.x] Fixed #29430 -- Clarified send_mail()'s fail_silently docs.

Backport of 085ebc5f1a0e96784516e551cb9225cc6836f1d0 from master