Prefetch's to_attr raises "Model" has no attribute "prefetched_field"

[Crocmagnon]

Bug report

What's wrong

class Tag(models.Model):
    pass

class Article(models.Model):
    tags = models.ManyToManyField(to=Tag, related_name="articles", blank=True)

    def method(self):
        published_articles = Article.objects.exclude(pk=self.pk)
        for tag in self.tags.all().prefetch_related(
            Prefetch("articles", published_articles, to_attr="published_articles")
        ):
            print(tag.published_articles)

src/articles/models.py:147: error: "Tag" has no attribute "published_articles"

How is that should be

published_articles should be recognized as a valid attribute for tag in the loop, as defined in the to_attr of the Prefetch instance.

System information

• OS: macOS 12.1 (21C52)
• python version: Python 3.10.0
• django version: 4.0
• mypy version: mypy 0.930
• django-stubs version: 1.9.0
• django-stubs-ext version: 0.3.1

[eddielu]

Anyone know any workarounds for this? I use this throughout my project, and I'm hesitant to throw around a bunch of # type:ignore[attr-defined] everywhere.

[eddielu]

Also, I'm curious what others have done when encountering this issue? Do you all just use type-ignore and move on?

[oliverhaas]

Also, I'm curious what others have done when encountering this issue? Do you all just use type-ignore and move on?

I just stumbled upon this, and I think the answer is that not that many people have this issue, since the exact combination of factors required are not insanely common (you need typing + prefetching + using to_attr).
And I expect this to be very difficult to implement...