Fixed #1 -- form instance is incorrectly propagated to other forms

composite_form/forms.py

@@ -10,8 +10,8 @@ class CompositeForm(forms.Form):
       class ProfileForm(CompositeForm):
           form_list = [ProfileAddressForm, ProfileBirthDayForm]
     """
-    form_list = None
-    _form_instances = {}
+    form_list = None  # Form classes
+    _form_instances = {}  # Form instances
 
     def __init__(self, data=None, files=None, *args, **initkwargs):
         if "instance" in initkwargs:
@@ -22,6 +22,9 @@ def __init__(self, data=None, files=None, *args, **initkwargs):
                 raise ValueError("instances should be a list the same lenth as form_list")
             if len(instances) != len(self.form_list):
                 raise ValueError("instances should be a list the same lenth as form_list")
+            for instance, form in zip(instances, self.form_list):
+                if instance is not None and not isinstance(instance, form._meta.model):
+                    raise ValueError
         self.is_bound = data is not None or files is not None
         self.instances = instances
 

example/tests/test_1.py

@@ -0,0 +1,36 @@
+# Regression test for https://github.com/t0ster/django-composite-form/issues/1
+
+from django.test import TestCase
+from django.contrib.auth.models import User
+
+
+from example.forms import ProfileForm, BaseProfileForm, UserCreationForm
+from example.models import Profile
+
+
+class FormsTests(TestCase):
+    def setUp(self):
+        profile_form = ProfileForm({
+            "address": "13 Test St",
+            "username": "test_user",
+            "password1": "123456",
+            "password2": "123456",
+        })
+        profile_form.save()
+        self.user = User.objects.all()[0]
+        self.profile = Profile.objects.all()[0]
+
+    def test_1(self):
+        profile_form = ProfileForm(instances=[self.user, self.profile])
+        self.assertEqual(profile_form.get_form(UserCreationForm).instance, self.user)
+        self.assertEqual(profile_form.get_form(BaseProfileForm).instance, self.profile)
+
+    def test_2(self):
+        profile_form = ProfileForm(instances=[self.user, None])
+        self.assertEqual(profile_form.get_form(UserCreationForm).instance, self.user)
+        self.assertIsInstance(profile_form.get_form(BaseProfileForm).instance, Profile)
+
+    def test_3(self):
+        profile_form = ProfileForm(instances=[None, self.profile])
+        self.assertEqual(profile_form.get_form(BaseProfileForm).instance, self.profile)
+        self.assertIsInstance(profile_form.get_form(UserCreationForm).instance, User)