Fixed #34187 -- Made UserCreationForm save many-to-many fields.

django/contrib/auth/forms.py

@@ -141,6 +141,8 @@ class UserCreationForm(forms.ModelForm):
         user.set_password(self.cleaned_data["password1"])
         if commit:
             user.save()
+            if hasattr(self, "save_m2m"):
+                self.save_m2m()
         return user
 
 

docs/releases/4.2.txt

@@ -65,6 +65,9 @@ Minor features
 * The default iteration count for the PBKDF2 password hasher is increased from
   390,000 to 480,000.
 
+* :class:`~django.contrib.auth.forms.UserCreationForm` now saves many-to-many
+  form fields for a custom user model.
+
 :mod:`django.contrib.contenttypes`
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

docs/topics/auth/customizing.txt

@@ -840,6 +840,11 @@ extend these forms in this manner::
             model = CustomUser
             fields = UserCreationForm.Meta.fields + ('custom_field',)
 
+.. versionchanged:: 4.2
+
+    In older versions, :class:`~django.contrib.auth.forms.UserCreationForm`
+    didn't save many-to-many form fields for a custom user model.
+
 Custom users and :mod:`django.contrib.admin`
 --------------------------------------------
 

docs/topics/auth/default.txt

@@ -1665,6 +1665,11 @@ provides several built-in forms located in :mod:`django.contrib.auth.forms`:
     sets the user's password using
     :meth:`~django.contrib.auth.models.User.set_password()`.
 
+    .. versionchanged:: 4.2
+
+        In older versions, :class:`UserCreationForm` didn't save many-to-many
+        form fields for a custom user model.
+
 .. currentmodule:: django.contrib.auth
 
 Authentication data in templates

tests/auth_tests/test_forms.py

@@ -35,6 +35,7 @@ from .models.custom_user import (
 )
 from .models.with_custom_email_field import CustomEmailField
 from .models.with_integer_username import IntegerUsernameUser
+from .models.with_many_to_many import CustomUserWithM2M, Organization
 from .settings import AUTH_TEMPLATES
 
 
@@ -252,6 +253,25 @@ class UserCreationFormTest(TestDataMixin, TestCase):
         form = CustomUserCreationForm(data)
         self.assertTrue(form.is_valid())
 
+    def test_custom_form_saves_many_to_many_field(self):
+        class CustomUserCreationForm(UserCreationForm):
+            class Meta(UserCreationForm.Meta):
+                model = CustomUserWithM2M
+                fields = UserCreationForm.Meta.fields + ("orgs",)
+
+        organization = Organization.objects.create(name="organization 1")
+
+        data = {
+            "username": "testclient@example.com",
+            "password1": "testclient",
+            "password2": "testclient",
+            "orgs": [str(organization.pk)],
+        }
+        form = CustomUserCreationForm(data)
+        self.assertIs(form.is_valid(), True)
+        user = form.save(commit=True)
+        self.assertSequenceEqual(user.orgs.all(), [organization])
+
     def test_password_whitespace_not_stripped(self):
         data = {
             "username": "testuser",