[Django] #32937: Form.get_initial_for_field() can return different values if called more than once
Django
than once
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Reporter: Chris Jerdonek | Owner: nobody
Type: Uncategorized | Status: new
Component: Forms | Version: dev
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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Currently,
[https://github.com/django/django/blob/304f6ff46a9d78aab0213b599356d3c7875b0bb9/django/forms/forms.py#L470-L478
Form.get_initial_for_field()] is
[https://docs.djangoproject.com/en/3.2/ref/forms/api/#django.forms.Form.get_initial_for_field
documented] as a way to retrieve the initial data for a form field.
However, it has the problem that it doesn't cache its return values, like
[https://github.com/django/django/blob/304f6ff46a9d78aab0213b599356d3c7875b0bb9/django/forms/boundfield.py#L229-L237
BoundField.initial] does, which can lead to buggy behavior e.g. in the
case of callables that return different values each time.
One way to fix this would be for `get_initial_for_field()` to get its
value from `BoundField` when it needs to fall back to the field, which can
then cache it (similar to how `BoundField.initial` caches its return
value). The downside of this is that it adds another layer of indirection,
as `BoundField.initial` is already going to `Form.get_initial_for_field()`
for its value. Another option might be to deprecate
`get_initial_for_field()`, as I'm not sure if it provides any benefit that
an API on `BoundField` couldn't better provide.
See also #32933.
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Ticket URL: <https://code.djangoproject.com/ticket/32937>
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Django
than once
Reporter: Chris Jerdonek | Owner: nobody
Type: Uncategorized | Status: new
Component: Forms | Version: dev
Keywords: | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
Comment (by Carlton Gibson):
Hey Chris.
Given #32933 — pointing users to `BoundField.initial`, would you object to
just documenting this?
We could add a paragraph in
https://docs.djangoproject.com/en/3.2/ref/forms/api/#dynamic-initial-
values saying _Why_ `BoundField.initial` is preferred: simpler interface,
and caches values, which matters for callables, like `now()`.
What do you think? I'm not sure we get much benefit adding yet more code
to this one… 🤔
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Ticket URL: <https://code.djangoproject.com/ticket/32937#comment:1>
Django
than once
Reporter: Chris Jerdonek | Owner: nobody
Type: Uncategorized | Status: new
Component: Forms | Version: dev
Keywords: | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
Comment (by Chris Jerdonek):
Thanks, Carlton. Yes, something like that would be good and was along the
lines of what I was thinking. I wasn't sure which direction you'd want to
go until filing the ticket. So maybe this issue can be closed, and I can
add a comment to the doc ticket linking to this.
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Ticket URL: <https://code.djangoproject.com/ticket/32937#comment:2>
Django
than once
Reporter: Chris Jerdonek | Owner: nobody
Component: Forms | Version: dev
Severity: Normal | Resolution: duplicate
Keywords: | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
Changes (by Carlton Gibson):
* status: new => closed
* resolution: => duplicate
Comment:
Agreed. Thanks.
Duplicate of #32933
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Ticket URL: <https://code.djangoproject.com/ticket/32937#comment:3>