[1.8.x] Fixed #24377 -- Fixed model inline formsets with primary key's that have defaults.

Backport of 1306cd1e8a from master

django/forms/models.py

@@ -788,7 +788,10 @@ class BaseModelFormSet(BaseFormSet):
                 or (pk.rel and pk.rel.parent_link and pk_is_not_editable(pk.rel.to._meta.pk)))
         if pk_is_not_editable(pk) or pk.name not in form.fields:
             if form.is_bound:
-                pk_value = form.instance.pk
+                # If we're adding the related instance, ignore its primary key
+                # as it could be an auto-generated default which isn't actually
+                # in the database.
+                pk_value = None if form.instance._state.adding else form.instance.pk
             else:
                 try:
                     if index is not None:
@@ -915,6 +918,11 @@ class BaseInlineFormSet(BaseModelFormSet):
             if self.fk.rel.field_name != self.fk.rel.to._meta.pk.name:
                 kwargs['to_field'] = self.fk.rel.field_name
 
+        # If we're adding a new object, ignore a parent's auto-generated pk
+        # as it will be regenerated on the save request.
+        if self.instance._state.adding and form._meta.model._meta.pk.has_default():
+            self.instance.pk = None
+
         form.fields[name] = InlineForeignKeyField(self.instance, **kwargs)
 
         # Add the generated field to form._meta.fields if it's defined to make

tests/model_formsets/models.py

@@ -1,6 +1,7 @@
 from __future__ import unicode_literals
 
 import datetime
+import uuid
 
 from django.db import models
 from django.utils import six
@@ -241,3 +242,15 @@ class Post(models.Model):
 
     def __str__(self):
         return self.name
+
+
+# Models for testing UUID primary keys
+class UUIDPKParent(models.Model):
+    uuid = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
+    name = models.CharField(max_length=255)
+
+
+class UUIDPKChild(models.Model):
+    uuid = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
+    name = models.CharField(max_length=255)
+    parent = models.ForeignKey(UUIDPKParent)

tests/model_formsets/test_uuid.py

@@ -0,0 +1,32 @@
+from django.forms.models import inlineformset_factory
+from django.test import TestCase
+
+from .models import UUIDPKChild, UUIDPKParent
+
+
+class InlineFormsetTests(TestCase):
+    def test_inlineformset_factory_nulls_default_pks(self):
+        """
+        #24377 - If we're adding a new object, a parent's auto-generated pk
+        from the model field default should be ignored as it's regenerated on
+        the save request.
+        """
+        FormSet = inlineformset_factory(UUIDPKParent, UUIDPKChild, fields='__all__')
+        formset = FormSet()
+        self.assertIsNone(formset.forms[0].fields['parent'].initial)
+
+    def test_inlineformset_factory_ignores_default_pks_on_submit(self):
+        """
+        #24377 - Inlines with a model field default should ignore that default
+        value to avoid triggering validation on empty forms.
+        """
+        FormSet = inlineformset_factory(UUIDPKParent, UUIDPKChild, fields='__all__')
+        formset = FormSet({
+            'uuidpkchild_set-TOTAL_FORMS': 3,
+            'uuidpkchild_set-INITIAL_FORMS': 0,
+            'uuidpkchild_set-MAX_NUM_FORMS': '',
+            'uuidpkchild_set-0-name': 'Foo',
+            'uuidpkchild_set-1-name': '',
+            'uuidpkchild_set-2-name': '',
+        })
+        self.assertTrue(formset.is_valid())