Fixed #27377 -- Clarified that prepopulated_fields doesn't work with OneToOneField.

AUTHORS

@@ -299,6 +299,7 @@ answer newbie questions, and generally made Django that much better:
     Hawkeye
     Helen Sherwood-Taylor <helen@rrdlabs.co.uk>
     Henrique Romano <onaiort@gmail.com>
+    Henry Dang <henrydangprg@gmail.com>
     hipertracker@gmail.com
     Hiroki Kiyohara <hirokiky@gmail.com>
     Honza Král <honza.kral@gmail.com>

django/contrib/admin/checks.py

@@ -399,7 +399,7 @@ class BaseModelAdminChecks(object):
                 return [
                     checks.Error(
                         "The value of '%s' refers to '%s', which must not be a DateTimeField, "
-                        "a ForeignKey, or a ManyToManyField." % (label, field_name),
+                        "a ForeignKey, a OneToOneField, or a ManyToManyField." % (label, field_name),
                         obj=obj.__class__,
                         id='admin.E028',
                     )

docs/ref/checks.txt

@@ -343,8 +343,8 @@ with the admin site:
 * **admin.E027**: The value of ``prepopulated_fields`` refers to
   ``<field name>``, which is not an attribute of ``<model>``.
 * **admin.E028**: The value of ``prepopulated_fields`` refers to
-  ``<field name>``, which must not be a ``DateTimeField``, a ``ForeignKey``, or a
+  ``<field name>``, which must not be a ``DateTimeField``, a ``ForeignKey``,
-  ``ManyToManyField`` field.
+  a ``OneToOneField``, or a ``ManyToManyField`` field.
 * **admin.E029**: The value of ``prepopulated_fields[<field name>]`` must be a
   list or tuple.
 * **admin.E030**: The value of ``prepopulated_fields`` refers to

docs/ref/contrib/admin/index.txt

@@ -1059,7 +1059,7 @@ subclass::
     slug (e.g. substituting dashes for spaces).
 
     ``prepopulated_fields`` doesn't accept ``DateTimeField``, ``ForeignKey``,
-    nor ``ManyToManyField`` fields.
+    ``OneToOneField``, and ``ManyToManyField`` fields.
 
 .. attribute:: ModelAdmin.preserve_filters
 

tests/modeladmin/models.py

@@ -36,6 +36,7 @@ class ValidationTestModel(models.Model):
     is_active = models.BooleanField(default=False)
     pub_date = models.DateTimeField()
     band = models.ForeignKey(Band, models.CASCADE)
+    best_friend = models.OneToOneField(User, models.CASCADE)
     # This field is intentionally 2 characters long (#16080).
     no = models.IntegerField(verbose_name="Number", blank=True, null=True)
 

tests/modeladmin/tests.py

@@ -1006,8 +1006,8 @@ class PrepopulatedFieldsCheckTests(CheckTestCase):
 
         self.assertIsInvalid(
             ValidationTestModelAdmin, ValidationTestModel,
-            ("The value of 'prepopulated_fields' refers to 'users', which must not be "
+            "The value of 'prepopulated_fields' refers to 'users', which must not be "
-             "a DateTimeField, a ForeignKey, or a ManyToManyField."),
+            "a DateTimeField, a ForeignKey, a OneToOneField, or a ManyToManyField.",
             'admin.E028')
 
     def test_valid_case(self):
@@ -1016,6 +1016,17 @@ class PrepopulatedFieldsCheckTests(CheckTestCase):
 
         self.assertIsValid(ValidationTestModelAdmin, ValidationTestModel)
 
+    def test_one_to_one_field(self):
+        class ValidationTestModelAdmin(ModelAdmin):
+            prepopulated_fields = {'best_friend': ('name',)}
+
+        self.assertIsInvalid(
+            ValidationTestModelAdmin, ValidationTestModel,
+            "The value of 'prepopulated_fields' refers to 'best_friend', which must not be "
+            "a DateTimeField, a ForeignKey, a OneToOneField, or a ManyToManyField.",
+            'admin.E028'
+        )
+
 
 class ListDisplayTests(CheckTestCase):