#30407: Modelform initial values override instance values when both are set
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Reporter: Alper Cugun | Owner: nobody
Type: Bug | Status: new
Component: Forms | Version: 2.2
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 1
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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We ran into a bug (on our side) where our data was not being displayed in
a ModelForm for existing instance because we were setting both initial
values as the instance in the ModelForm.
Digging into the documentation it turns out that for [ModelForm initial
overrides instance values
https://docs.djangoproject.com/en/2.2/topics/forms/modelforms/#providing-
initial-values] ("Initial values provided this way will override both
initial values from the form field and values from an attached model
instance.") whereas for [normal Forms initial
https://docs.djangoproject.com/en/2.2/ref/forms/api/#dynamic-initial-
values] does not take precedence over bound data ("These values are only
displayed for unbound forms, and they’re not used as fallback values if a
particular value isn’t provided."). Maybe that's my mistake for thinking a
bound Form and a ModelForm with an instance are roughly equivalent.
I tracked this down to [this commit
https://github.com/django/django/commit/51dc4ecf943d1dcc044ed956925760f9d480f56c]
12 years ago and it seems that nobody has complained much about this piece
of code in the mean time. So maybe it isn't a problem but I think there is
something to be said for reversing the precedence in ModelForm.
I've attached a draft diff to fix this.
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Ticket URL: <https://code.djangoproject.com/ticket/30407>
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