Fixed #25241 -- Corrected ModelForm.save() error message when saving invalid…

Fixed #25241 -- Corrected ModelForm.save() error message when saving invalid form with UUIDField pk.

django/forms/models.py

@@ -454,7 +454,7 @@ class BaseModelForm(BaseForm):
         If commit=True, then the changes to ``instance`` will be saved to the
         database. Returns ``instance``.
         """
-        if self.instance.pk is None:
+        if self.instance._state.adding:
             fail_message = 'created'
         else:
             fail_message = 'changed'

tests/model_forms/models.py

@@ -11,6 +11,7 @@ from __future__ import unicode_literals
 import datetime
 import os
 import tempfile
+import uuid
 
 from django.core import validators
 from django.core.exceptions import ValidationError
@@ -447,3 +448,8 @@ class Photo(models.Model):
     def save(self, force_insert=False, force_update=False):
         super(Photo, self).save(force_insert, force_update)
         self._savecount += 1
+
+
+class UUIDPK(models.Model):
+    uuid = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
+    name = models.CharField(max_length=30)

tests/model_forms/test_uuid.py

+from __future__ import unicode_literals
+
+from django import forms
+from django.test import TestCase
+
+from .models import UUIDPK
+
+
+class UUIDPKForm(forms.ModelForm):
+    class Meta:
+        model = UUIDPK
+        fields = '__all__'
+
+
+class ModelFormBaseTest(TestCase):
+    def test_create_save_error(self):
+        form = UUIDPKForm({})
+        self.assertFalse(form.is_valid())
+        msg = "The UUIDPK could not be created because the data didn't validate."
+        with self.assertRaisesMessage(ValueError, msg):
+            form.save()
+
+    def test_update_save_error(self):
+        obj = UUIDPK.objects.create(name='foo')
+        form = UUIDPKForm({}, instance=obj)
+        self.assertFalse(form.is_valid())
+        msg = "The UUIDPK could not be changed because the data didn't validate."
+        with self.assertRaisesMessage(ValueError, msg):
+            form.save()

tests/model_forms/tests.py

@@ -1978,7 +1978,7 @@ class FileAndImageFieldTests(TestCase):
         form = FPForm()
         names = [p[1] for p in form['path'].field.choices]
         names.sort()
-        self.assertEqual(names, ['---------', '__init__.py', 'models.py', 'tests.py'])
+        self.assertEqual(names, ['---------', '__init__.py', 'models.py', 'test_uuid.py', 'tests.py'])
 
     @skipUnless(test_images, "Pillow not installed")
     def test_image_field(self):