#32549: Add `Q.empty()` to check for nested empty Q objects like `Q(Q())`
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Reporter: jonathan-golorry | Owner: nobody
Type: | Status: closed
Cleanup/optimization |
Component: Database layer | Version: dev
(models, ORM) |
Severity: Normal | Resolution: wontfix
Keywords: Q objects, nested, | Triage Stage:
empty | Unreviewed
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by jonathan-golorry):
We already shortcut logical operations between empty Q objects, so I view
this more as an extension of that shortcutting (for legibility, not
performance). I don't think it's fair to say it's backwards incompatible,
since the simplified Q objects will be logically equivalent to the old
ones. The expected outcome of Q object combinations is logical
consistency, not a specific tree structure (as evidenced by `len((Q(x=1,
y=2) | Q(x=1, y=2)).children == 1)`.
My original example shows why it's desirable to have `q.empty()` behave
differently from `not bool(q)`. Empty Q objects are a potential security
risk, but the standard way to check for them doesn't catch nested empty Q
objects. #32554 doesn't actually build nested queries, it just uses this
to avoid bugs with nested query inputs.
My apologies for reopening without a mailing list consensus, though I feel
"If there is a way they can improve the ticket to reopen it, let them
know" indicates that I may reopen if I address the only concern you
expressed in your closing comment. If the reason for closing is that
legibility of Q objects isn't it's own concern, I can roll `empty` into
#32554 without the logic shortcut.
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Ticket URL: <https://code.djangoproject.com/ticket/32549#comment:5>
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