Fixed #10792 -- Ensured that ModelChoiceFields don't provide an empty option when the underlying field has blank=False and there is a default value available. Thanks to carljm for the report and patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@10729 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/forms/models.py

@@ -896,7 +896,10 @@ class ModelChoiceField(ChoiceField):
     def __init__(self, queryset, empty_label=u"---------", cache_choices=False,
                  required=True, widget=None, label=None, initial=None,
                  help_text=None, to_field_name=None, *args, **kwargs):
-        self.empty_label = empty_label
+        if required and (initial is not None):
+            self.empty_label = None
+        else:
+            self.empty_label = empty_label
         self.cache_choices = cache_choices
 
         # Call Field instead of ChoiceField __init__() because we don't need

docs/ref/forms/fields.txt

@@ -786,6 +786,10 @@ example::
         # No empty label
         field2 = forms.ModelChoiceField(queryset=..., empty_label=None)
 
+   Note that if a ``ModelChoiceField`` is required and has a default
+   initial value, no empty choice is created (regardless of the value
+   of ``empty_label``).
+
 ``ModelMultipleChoiceField``
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

tests/regressiontests/forms/models.py

@@ -24,6 +24,17 @@ class ChoiceModel(models.Model):
     """For ModelChoiceField and ModelMultipleChoiceField tests."""
     name = models.CharField(max_length=10)
 
+class ChoiceOptionModel(models.Model):
+    """Destination for ChoiceFieldModel's ForeignKey.
+    Can't reuse ChoiceModel because error_message tests require that it have no instances."""
+    name = models.CharField(max_length=10)
+
+class ChoiceFieldModel(models.Model):
+    """Model with ForeignKey to another model, for testing ModelForm
+    generation with ModelChoiceField."""
+    choice = models.ForeignKey(ChoiceOptionModel, blank=False,
+                               default=lambda: ChoiceOptionModel.objects.all()[0])
+
 class FileModel(models.Model):
     file = models.FileField(storage=temp_storage, upload_to='tests')
 
@@ -105,4 +116,19 @@ u'class default value'
 >>> obj.def_date
 datetime.date(1999, 3, 2)
 >>> shutil.rmtree(temp_storage_location)
+
+In a ModelForm with a ModelChoiceField, if the model's ForeignKey has blank=False and a default,
+no empty option is created (regression test for #10792).
+
+First we need at least one instance of ChoiceOptionModel:
+
+>>> ChoiceOptionModel.objects.create(name='default')
+<ChoiceOptionModel: ChoiceOptionModel object>
+
+>>> class ChoiceFieldForm(ModelForm):
+...     class Meta:
+...         model = ChoiceFieldModel
+>>> list(ChoiceFieldForm().fields['choice'].choices)
+[(1, u'ChoiceOptionModel object')]
+
 """}