#16995: ModelFormSet initial data from initial parameter uses "extra" forms
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Reporter: p910221@… | Owner: nobody
Type: Bug | Status: new
Component: Documentation | Version: SVN
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Changes (by carljm):
* needs_better_patch: => 0
* component: Forms => Documentation
* needs_tests: => 0
* version: 1.3 => SVN
* needs_docs: => 0
* stage: Unreviewed => Accepted
Comment:
I believe this is working as designed. I do, however, think the
documentation is lacking in clarity and there's an inconsistency with how
`initial` works in a regular `FormSet`.
With a `FormSet`, `extra` forms are those beyond the ones created by the
data in `initial`, as
[https://docs.djangoproject.com/en/dev/topics/forms/formsets/#using-
initial-data-with-a-formset documented here].
With a `ModelFormSet`, the data in the non-extra forms is determined by
the existing model instances. It's sometimes useful to be able to pre-
populate some of the extra forms with some initial data, and that's what
the `initial` parameter is used for. If `initial` pre-populated the non-
extra forms, how would the conflict with existing model instance data be
resolved?
If this were being designed from scratch, you could perhaps make a case
that a `ModelFormSet` should consist of first the forms representing
existing instances, then forms representing the given `initial` data, then
empty `extra` forms (i.e. `initial` would add more forms, not prepopulate
the `extra` forms). This would perhaps be more consistent with `FormSet`,
but I'm not sure it's actually better for real usage.
In any case, if it's an improvement at all, it's not enough of one to
justify making a backwards-incompatible change. So I'm converting this
into a documentation bug; the `ModelFormSet`
[https://docs.djangoproject.com/en/dev/topics/forms/modelforms/#model-
formsets docs] should have an explanation of how `initial` and `extra`
interact differently in a `ModelFormSet` than in a `FormSet`.
--
Ticket URL: <https://code.djangoproject.com/ticket/16995#comment:1>
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