Fixed #21259 -- Fixed formstools wizard for InlineFormSet.

django/contrib/formtools/tests/models.py

+# coding: utf-8
+from django.db import models
+from django.utils.encoding import python_2_unicode_compatible
+
+
+@python_2_unicode_compatible
+class Poet(models.Model):
+    name = models.CharField(max_length=100)
+
+    class Meta:
+        app_label = 'formtools'
+
+    def __str__(self):
+        return self.name
+
+
+@python_2_unicode_compatible
+class Poem(models.Model):
+    poet = models.ForeignKey(Poet)
+    name = models.CharField(max_length=100)
+
+    class Meta:
+        app_label = 'formtools'
+
+    def __str__(self):
+        return self.name

django/contrib/formtools/tests/wizard/wizardtests/tests.py

@@ -10,6 +10,7 @@ from django.contrib.auth.models import User
 from django.contrib.auth.tests.utils import skipIfCustomUser
 from django.contrib.formtools.wizard.views import CookieWizardView
 from django.utils._os import upath
+from django.contrib.formtools.tests.models import Poet, Poem
 
 
 class UserForm(forms.ModelForm):
@@ -19,6 +20,7 @@ class UserForm(forms.ModelForm):
 
 
 UserFormSet = forms.models.modelformset_factory(User, form=UserForm, extra=2)
+PoemFormSet = forms.models.inlineformset_factory(Poet, Poem, fields="__all__")
 
 
 class WizardTests(object):
@@ -405,3 +407,25 @@ class WizardFormKwargsOverrideTests(TestCase):
         self.assertEqual(formset.initial_form_count(), 1)
         self.assertEqual(['staff@example.com'],
             list(formset.queryset.values_list('email', flat=True)))
+
+
+class WizardInlineFormSetTests(TestCase):
+    def setUp(self):
+        self.rf = RequestFactory()
+        self.poet = Poet.objects.create(name='test')
+        self.poem = self.poet.poem_set.create(name='test poem')
+
+    def test_set_instance(self):
+        # Regression test for #21259
+        poet = self.poet
+        class InlineFormSetWizard(CookieWizardView):
+            instance = None
+            def get_form_instance(self, step):
+                if self.instance is None:
+                    self.instance = poet
+                return self.instance
+
+        view = InlineFormSetWizard.as_view([PoemFormSet])
+        response = view(self.rf.get('/'))
+        formset = response.context_data['wizard']['form']
+        self.assertEqual(formset.instance, self.poet)

django/contrib/formtools/wizard/views.py

@@ -398,23 +398,24 @@ class WizardView(TemplateView):
         """
         if step is None:
             step = self.steps.current
+        form_class = self.form_list[step]
         # prepare the kwargs for the form instance.
         kwargs = self.get_form_kwargs(step)
         kwargs.update({
             'data': data,
             'files': files,
-            'prefix': self.get_form_prefix(step, self.form_list[step]),
+            'prefix': self.get_form_prefix(step, form_class),
             'initial': self.get_form_initial(step),
         })
-        if issubclass(self.form_list[step], forms.ModelForm):
-            # If the form is based on ModelForm, add instance if available
-            # and not previously set.
+        if issubclass(form_class, (forms.ModelForm, forms.models.BaseInlineFormSet)):
+            # If the form is based on ModelForm or InlineFormSet,
+            # add instance if available and not previously set.
             kwargs.setdefault('instance', self.get_form_instance(step))
-        elif issubclass(self.form_list[step], forms.models.BaseModelFormSet):
+        elif issubclass(form_class, forms.models.BaseModelFormSet):
             # If the form is based on ModelFormSet, add queryset if available
             # and not previous set.
             kwargs.setdefault('queryset', self.get_form_instance(step))
-        return self.form_list[step](**kwargs)
+        return form_class(**kwargs)
 
     def process_step(self, form):
         """