Invalid related_name passes silently

[Konrad Świat]

Invalid related_name e.g. 'user sets' passes silently. It leads to unpredictable problems. It is not a bug, nor new feature, just RelatedField.check() little iprovement.

[Baptiste Mispelon]

Good idea, that sounds like a perfect use-case for the checks framework.

[Konrad Świat]

​https://github.com/kswiat/django/tree/ticket_22064
work in progress (tests)

[Akshay Katyal <ktyaks@…>]

Is anyone working on this? Been about 3 months since the last commit on the branch.

[Tim Graham]

The commit in comment 3 looks like a good start. There's a comment there that says, "There is a problem with regex performance, it must be solved before pull request" so if someone wants to take a look, that would be helpful.

[André Ericson]

Curious if the problem with regex is the fact that the commit uses two regexes or is it that he uses regex at all?

I mean would it be preferable to have a faster less readable regex-free solution or a slower more readable using regex?

Please read this as a general question from someone new here rather than as specific to this ticket.

[Carl Meyer]

The checks framework is not a runtime code path or a fast path at all, so readability definitely trumps performance here. Barring catastrophic performance issues, which a complex regex can be susceptible to.

Looking at the draft patch commit, a few comments:

1. I don't see why the "ends with +" case needs any regex at all. Any related-name ending with "+" is valid, since it won't be used as a Python identifier anyway. (I'm not sure why we even support "ends with +" rather than just "+" -- what's the purpose of including anything before the "+"?). So a simple .endswith('+') check should be sufficient there.

2. I'd suggest that we also check the related_name against keyword.iskeyword(), since using a Python keyword as a related name could also cause trouble.

[André Ericson]

Thanks for your comments I'll be submitting a patch.

[André Ericson]

Assigned it to myself as it seems to be inactive for months.
Submitted a new patch.

pull request at: ​https://github.com/django/django/pull/3308

[André Ericson <de.ericson@…>]

In 1e5e2a470768549117ac4696ce3e8b4e51d65664:

Fixed #22064 -- Add check for related_name

Validates that related_name is a valid Python id or ends with a '+' and
it's not a keyword. Without a check it passed silently leading to
unpredictable problems.

Thanks Konrad Świat for the initial work.

[Carl Meyer <carl@…>]

In 6f6e7d01dce94668e178b26da547c4643ed3a6cc:

Merge pull request #3308 from aericson/ticket_22064

Fixed #22064 -- Add check for related_name