Add tests for HTML_CUTOFF setting and fix issue where setting it to None would raise an exception.

rest_framework/relations.py

@@ -75,7 +75,8 @@ class PKOnlyObject(object):
 # rather than the parent serializer.
 MANY_RELATION_KWARGS = (
     'read_only', 'write_only', 'required', 'default', 'initial', 'source',
-    'label', 'help_text', 'style', 'error_messages', 'allow_empty'
+    'label', 'help_text', 'style', 'error_messages', 'allow_empty',
+    'html_cutoff', 'html_cutoff_text'
 )
 
 
@@ -86,10 +87,12 @@ class RelatedField(Field):
 
     def __init__(self, **kwargs):
         self.queryset = kwargs.pop('queryset', self.queryset)
-        self.html_cutoff = kwargs.pop(
-            'html_cutoff',
-            self.html_cutoff or int(api_settings.HTML_SELECT_CUTOFF)
-        )
+
+        cutoff_from_settings = api_settings.HTML_SELECT_CUTOFF
+        if cutoff_from_settings is not None:
+            cutoff_from_settings = int(cutoff_from_settings)
+        self.html_cutoff = kwargs.pop('html_cutoff', cutoff_from_settings)
+
         self.html_cutoff_text = kwargs.pop(
             'html_cutoff_text',
             self.html_cutoff_text or _(api_settings.HTML_SELECT_CUTOFF_TEXT)
@@ -466,10 +469,12 @@ class ManyRelatedField(Field):
     def __init__(self, child_relation=None, *args, **kwargs):
         self.child_relation = child_relation
         self.allow_empty = kwargs.pop('allow_empty', True)
-        self.html_cutoff = kwargs.pop(
-            'html_cutoff',
-            self.html_cutoff or int(api_settings.HTML_SELECT_CUTOFF)
-        )
+
+        cutoff_from_settings = api_settings.HTML_SELECT_CUTOFF
+        if cutoff_from_settings is not None:
+            cutoff_from_settings = int(cutoff_from_settings)
+        self.html_cutoff = kwargs.pop('html_cutoff', cutoff_from_settings)
+
         self.html_cutoff_text = kwargs.pop(
             'html_cutoff_text',
             self.html_cutoff_text or _(api_settings.HTML_SELECT_CUTOFF_TEXT)

tests/test_relations.py

 import uuid
 
 import pytest
+from _pytest.monkeypatch import MonkeyPatch
 from django.conf.urls import url
 from django.core.exceptions import ImproperlyConfigured
 from django.test import override_settings
 from django.utils.datastructures import MultiValueDict
 
-from rest_framework import serializers
+from rest_framework import relations, serializers
 from rest_framework.fields import empty
 from rest_framework.test import APISimpleTestCase
 
@@ -25,6 +26,61 @@ class TestStringRelatedField(APISimpleTestCase):
         assert representation == '<MockObject name=foo, pk=1>'
 
 
+class MockApiSettings(object):
+    def __init__(self, cutoff, cutoff_text):
+        self.HTML_SELECT_CUTOFF = cutoff
+        self.HTML_SELECT_CUTOFF_TEXT = cutoff_text
+
+
+class TestRelatedFieldHTMLCutoff(APISimpleTestCase):
+    def setUp(self):
+        self.queryset = MockQueryset([
+            MockObject(pk=i, name=str(i)) for i in range(0, 1100)
+        ])
+        self.monkeypatch = MonkeyPatch()
+
+    def test_no_settings(self):
+        # The default is 1,000, so sans settings it should be 1,000 plus one.
+        for many in (False, True):
+            field = serializers.PrimaryKeyRelatedField(queryset=self.queryset,
+                                                       many=many)
+            options = list(field.iter_options())
+            assert len(options) == 1001
+            assert options[-1].display_text == "More than 1000 items..."
+
+    def test_settings_cutoff(self):
+        self.monkeypatch.setattr(relations, "api_settings",
+                                 MockApiSettings(2, "Cut Off"))
+        for many in (False, True):
+            field = serializers.PrimaryKeyRelatedField(queryset=self.queryset,
+                                                       many=many)
+            options = list(field.iter_options())
+            assert len(options) == 3  # 2 real items plus the 'Cut Off' item.
+            assert options[-1].display_text == "Cut Off"
+
+    def test_settings_cutoff_none(self):
+        # Setting it to None should mean no limit; the default limit is 1,000.
+        self.monkeypatch.setattr(relations, "api_settings",
+                                 MockApiSettings(None, "Cut Off"))
+        for many in (False, True):
+            field = serializers.PrimaryKeyRelatedField(queryset=self.queryset,
+                                                       many=many)
+            options = list(field.iter_options())
+            assert len(options) == 1100
+
+    def test_settings_kwargs_cutoff(self):
+        # The explicit argument should override the settings.
+        self.monkeypatch.setattr(relations, "api_settings",
+                                 MockApiSettings(2, "Cut Off"))
+        for many in (False, True):
+            field = serializers.PrimaryKeyRelatedField(queryset=self.queryset,
+                                                       many=many,
+                                                       html_cutoff=100)
+            options = list(field.iter_options())
+            assert len(options) == 101
+            assert options[-1].display_text == "Cut Off"
+
+
 class TestPrimaryKeyRelatedField(APISimpleTestCase):
     def setUp(self):
         self.queryset = MockQueryset([

tests/utils.py

@@ -20,6 +20,9 @@ class MockQueryset(object):
     def __init__(self, iterable):
         self.items = iterable
 
+    def __getitem__(self, val):
+        return self.items[val]
+
     def get(self, **lookup):
         for item in self.items:
             if all([