Hidden empty form on formset for InlineAdminForm

Using Django The Admin
1

In the page for a ModelAdmin with an inline, the inline formset will always inlcude one more extra inline than I asked for. (It’s hidden by the admin page’s CSS and has the class empty-form) .

Even if extra = 0 on the InlineModelAdmin, this form is added to the formset.

The extra form is not present in the formset itself when it’s first created. For example:

>>> FormSet = inlineformset_factory(ParentModel, ChildModel, fields="__all__", extra=0) # create a FormSet class
>>> fs = FS(instance= ParentModel.objects.get(pk=1))  # create a formset instance

I get the expected number of inline admin forms (i.e. 0), with no hidden extras.

Why is this extra inline form created, and how do I get rid of it?

I thought if it might be related to edit_only, and whether:

class MyInline(admin.TabularInline):
    model = ChildModel
    formset = inlineformset_factory(ParentModel, ChildModel, extra=0, edit_only=True, fields="__all__")

would remove it - but while that seems to be the way to use a custom formset on an inline, it makes no difference at all to the behaviour of the InlineModelAdmin.

2

This appears to be an artifact of the template, created by having the has_add_permission on the TabularInline class. (see django.contrib.admin.templates.admin.edit_inline - tabular.html)

I don’t know right off-hand if you can just add a has_add_permission=False attribute to MyInline - I don’t think it’s going to work because I believe the __init__ method for that class would override it.

My guess is you would need to override has_add_permission on the class to set it False.
e.g.

class MyInline(admin.TabularInline):
  model = ChildModel

  def has_add_permission(self, request, obj):
    return False

Again - I’ve never tried anything like this, it’s all conjecture at this point.

3

And that seems to be exactly the thing, thanks!