Fixed #21967: Added check for object in ModelFormMixin.get_form_kwargs.

Thanks lagovas.lagovas at gmail.com for the report.

django/views/generic/edit.py

@@ -122,6 +122,7 @@ class ModelFormMixin(FormMixin, SingleObjectMixin):
         Returns the keyword arguments for instantiating the form.
         """
         kwargs = super(ModelFormMixin, self).get_form_kwargs()
+        if hasattr(self, 'object'):
             kwargs.update({'instance': self.object})
         return kwargs
 

tests/generic_views/test_edit.py

@@ -9,7 +9,7 @@ from django import forms
 from django.test import TestCase
 from django.test.client import RequestFactory
 from django.views.generic.base import View
-from django.views.generic.edit import FormMixin, CreateView
+from django.views.generic.edit import FormMixin, ModelFormMixin, CreateView
 
 from . import views
 from .models import Artist, Author
@@ -55,6 +55,12 @@ class ModelFormMixinTests(TestCase):
         form_class = views.AuthorGetQuerySetFormView().get_form_class()
         self.assertEqual(form_class._meta.model, Author)
 
+    def test_get_form_checks_for_object(self):
+        mixin = ModelFormMixin()
+        mixin.request = RequestFactory().get('/')
+        self.assertEqual({'initial': {}, 'prefix': None},
+                         mixin.get_form_kwargs())
+
 
 class CreateViewTests(TestCase):
     urls = 'generic_views.urls'