Merge remote-tracking branch 'origin/master' into 2.4.0

Conflicts:
	.travis.yml
	docs/api-guide/fields.md
	docs/api-guide/routers.md
	docs/topics/release-notes.md
	rest_framework/authentication.py
	rest_framework/serializers.py
	rest_framework/templatetags/rest_framework.py
	rest_framework/tests/test_authentication.py
	rest_framework/tests/test_filters.py
	rest_framework/tests/test_hyperlinkedserializers.py
	rest_framework/tests/test_serializer.py
	rest_framework/tests/test_testing.py
	rest_framework/utils/encoders.py
	tox.ini

1 files changed, 20 insertions, 14 deletions

diff --git a/rest_framework/relations.py b/rest_framework/relations.py
index 4785c009..3b234dd5 100644
--- a/rest_framework/relations.py
+++ b/rest_framework/relations.py
@@ -33,6 +33,7 @@ class RelatedField(WritableField):
     many_widget = widgets.SelectMultiple
     form_field_class = forms.ChoiceField
     many_form_field_class = forms.MultipleChoiceField
+    null_values = (None, '', 'None')
 
     cache_choices = False
     empty_label = None
@@ -50,6 +51,8 @@ class RelatedField(WritableField):
         super(RelatedField, self).__init__(*args, **kwargs)
 
         if not self.required:
+            # Accessed in ModelChoiceIterator django/forms/models.py:1034
+            # If set adds empty choice.
             self.empty_label = BLANK_CHOICE_DASH[0][1]
 
         self.queryset = queryset
@@ -57,16 +60,11 @@ class RelatedField(WritableField):
     def initialize(self, parent, field_name):
         super(RelatedField, self).initialize(parent, field_name)
         if self.queryset is None and not self.read_only:
-            try:
-                manager = getattr(self.parent.opts.model, self.source or field_name)
-                if hasattr(manager, 'related'):  # Forward
-                    self.queryset = manager.related.model._default_manager.all()
-                else:  # Reverse
-                    self.queryset = manager.field.rel.to._default_manager.all()
-            except Exception:
-                msg = ('Serializer related fields must include a `queryset`' +
-                       ' argument or set `read_only=True')
-                raise Exception(msg)
+            manager = getattr(self.parent.opts.model, self.source or field_name)
+            if hasattr(manager, 'related'):  # Forward
+                self.queryset = manager.related.model._default_manager.all()
+            else:  # Reverse
+                self.queryset = manager.field.rel.to._default_manager.all()
 
     ### We need this stuff to make form choices work...
 
@@ -115,6 +113,14 @@ class RelatedField(WritableField):
 
     choices = property(_get_choices, _set_choices)
 
+    ### Default value handling
+
+    def get_default_value(self):
+        default = super(RelatedField, self).get_default_value()
+        if self.many and default is None:
+            return []
+        return default
+
     ### Regular serializer stuff...
 
     def field_to_native(self, obj, field_name):
@@ -163,11 +169,11 @@ class RelatedField(WritableField):
         except KeyError:
             if self.partial:
                 return
-            value = [] if self.many else None
+            value = self.get_default_value()
 
-        if value in (None, '') and self.required:
-            raise ValidationError(self.error_messages['required'])
-        elif value in (None, ''):
+        if value in self.null_values:
+            if self.required:
+                raise ValidationError(self.error_messages['required'])
             into[(self.source or field_name)] = None
         elif self.many:
             into[(self.source or field_name)] = [self.from_native(item) for item in value]