#36426: prefetch_related_objects() is doc'd to accept iterables but only accepts
sequences
-------------------------------------+-------------------------------------
Reporter: Jacob Walls | Owner: Luna
Type: | Status: assigned
Cleanup/optimization |
Component: Database layer | Version: dev
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 1 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by Natalia Bidart):
* version: 5.2 => dev
Comment:
Replying to [comment:4 Jacob Walls]:
> Sorry, I didn't realize I left out details: I figured
`next(iter(model_instances)))` would accept iterables simply.
Makes sense :-)
> > This keeps the expectations clear and avoids surprising behavior with
edge cases like passing a string or dictionary.
>
> Certainly a string makes no sense, but a string is both an iterable and
a sequence, so it's the same no matter what we choose here.
Good point.
> I'm not proposing we add a strict type check for model instances: the
current duck-typing approach seems fine.
I agree.
> I used `set` in the bug report, but where I encountered this in practice
was with a `dict_values`. I could have just as easily ended up trying
`dict` or `dict_keys`. I guess expected them all to just work.
Your points make sense and I think changing the code (with tests) to
replace `first_obj = obj_list[0]` with `next(iter(obj_list))` makes the
code more robust, and as you say, it aligns with the docs.
--
Ticket URL: <https://code.djangoproject.com/ticket/36426#comment:7>
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