How to filter choices in Django2's autocomplete_fields?

Question

In Django 2.0, autocomplete_fields was added, which is great.

Without autocomplete_fields, I can change the queryset of a ForeignKeyField using formfield_for_foreignkey.

But combining the two together doesn't work - it looks like the list of options for autocomplete is dynamic and coming from a different url, instead of from the current form.

So the question is -

How can I change the queryset in the autocomplete widget?

Answer 1

Override the ModelAdmin's get_search_results method to use the query you want. You can see in the get_queryset method for the view providing the data for autocomplete fields that it's used to get the queryset - the source as of this answer is https://github.com/django/django/blob/03dbdfd9bbbbd0b0172aad648c6bbe3f39541137/django/contrib/admin/views/autocomplete.py#L42.

Answer 2

If you are using autocomplete_fields for a ManyToManyField on 'self', this example will exclude the current object.

Get the current object's id by overriding get_form:

field_for_autocomplete = None

def get_form(self, request, obj=None, **kwargs):
    if obj:
        self.field_for_autocomplete = obj.pk

    return super(MyAdmin, self).get_form(request, obj, **kwargs)

Next, override get_search_results. Modify the queryset only for your model's autocomplete URI:

def get_search_results(self, request, queryset, search_term):
    queryset, use_distinct = super().get_search_results(request, queryset, search_term)

    # Exclude only for autocomplete
    if request.path == '/admin/myapp/mymodel/autocomplete/':
        queryset = queryset.exclude(field=self.field_for_autocomplete)

    return queryset, use_distinct