Adding `BLANK_CHOICE_DASH` as a choice if the model's field isn't required

rest_framework/fields.py

@@ -15,6 +15,7 @@ import warnings
 from django.core import validators
 from django.core.exceptions import ValidationError
 from django.conf import settings
+from django.db.models.fields import BLANK_CHOICE_DASH
 from django import forms
 from django.forms import widgets
 from django.utils.encoding import is_protected_type
@@ -402,6 +403,8 @@ class ChoiceField(WritableField):
     def __init__(self, choices=(), *args, **kwargs):
         super(ChoiceField, self).__init__(*args, **kwargs)
         self.choices = choices
+        if not self.required:
+            self.choices = BLANK_CHOICE_DASH + self.choices
 
     def _get_choices(self):
         return self._choices

rest_framework/tests/fields.py

@@ -646,3 +646,29 @@ class DecimalFieldTest(TestCase):
 
         self.assertFalse(s.is_valid())
         self.assertEqual(s.errors,  {'decimal_field': ['Ensure that there are no more than 4 digits in total.']})
+
+
+class ChoiceFieldTests(TestCase):
+    """
+    Tests for the ChoiceField options generator
+    """
+
+    SAMPLE_CHOICES = [
+        ('red', 'Red'),
+        ('green', 'Green'),
+        ('blue', 'Blue'),
+    ]
+
+    def test_choices_required(self):
+        """
+        Make sure proper choices are rendered if field is required
+        """
+        f = serializers.ChoiceField(required=True, choices=self.SAMPLE_CHOICES)
+        self.assertEqual(f.choices, self.SAMPLE_CHOICES)
+
+    def test_choices_not_required(self):
+        """
+        Make sure proper choices (plus blank) are rendered if the field isn't required
+        """
+        f = serializers.ChoiceField(required=False, choices=self.SAMPLE_CHOICES)
+        self.assertEqual(f.choices, models.fields.BLANK_CHOICE_DASH + self.SAMPLE_CHOICES)

rest_framework/tests/models.py

@@ -117,6 +117,32 @@ class OptionalRelationModel(RESTFrameworkModel):
     other = models.ForeignKey('OptionalRelationModel', blank=True, null=True)
 
 
+# Model for issue #725
+class SeveralChoicesModel(RESTFrameworkModel):
+    color = models.CharField(
+        max_length=10,
+        choices=[('red', 'Red'), ('green', 'Green'), ('blue', 'Blue')],
+        blank=False
+    )
+    drink = models.CharField(
+        max_length=10,
+        choices=[('beer', 'Beer'), ('wine', 'Wine'), ('cider', 'Cider')],
+        blank=False,
+        default='beer'
+    )
+    os = models.CharField(
+        max_length=10,
+        choices=[('linux', 'Linux'), ('osx', 'OSX'), ('windows', 'Windows')],
+        blank=True
+    )
+    music_genre = models.CharField(
+        max_length=10,
+        choices=[('rock', 'Rock'), ('metal', 'Metal'), ('grunge', 'Grunge')],
+        blank=True,
+        default='metal'
+    )
+
+
 # Model for RegexField
 class Book(RESTFrameworkModel):
     isbn = models.CharField(max_length=13)

rest_framework/tests/serializer.py

 from __future__ import unicode_literals
+from django.db.models.fields import BLANK_CHOICE_DASH
 from django.utils.datastructures import MultiValueDict
 from django.test import TestCase
 from rest_framework import serializers
 from rest_framework.tests.models import (HasPositiveIntegerAsChoice, Album, ActionItem, Anchor, BasicModel,
     BlankFieldModel, BlogPost, BlogPostComment, Book, CallableDefaultValueModel, DefaultValueModel,
-    ManyToManyModel, Person, ReadOnlyManyToManyModel, Photo)
+    ManyToManyModel, Person, ReadOnlyManyToManyModel, Photo, SeveralChoicesModel)
 import datetime
 import pickle
 
@@ -1018,6 +1019,48 @@ class SerializerPickleTests(TestCase):
         repr(pickle.loads(pickle.dumps(data, 0)))
 
 
+# test for issue #725
+class SerializerChoiceFields(TestCase):
+
+    def setUp(self):
+        super(SerializerChoiceFields, self).setUp()
+
+        class SeveralChoicesSerializer(serializers.ModelSerializer):
+            class Meta:
+                model = SeveralChoicesModel
+                fields = ('color', 'drink', 'os', 'music_genre')
+
+        self.several_choices_serializer = SeveralChoicesSerializer
+
+    def test_choices_blank_false_not_default(self):
+        serializer = self.several_choices_serializer()
+        self.assertEqual(
+            serializer.fields['color'].choices,
+            [('red', 'Red'), ('green', 'Green'), ('blue', 'Blue')]
+        )
+
+    def test_choices_blank_false_with_default(self):
+        serializer = self.several_choices_serializer()
+        self.assertEqual(
+            serializer.fields['drink'].choices,
+            [('beer', 'Beer'), ('wine', 'Wine'), ('cider', 'Cider')]
+        )
+
+    def test_choices_blank_true_not_default(self):
+        serializer = self.several_choices_serializer()
+        self.assertEqual(
+            serializer.fields['os'].choices,
+            BLANK_CHOICE_DASH + [('linux', 'Linux'), ('osx', 'OSX'), ('windows', 'Windows')]
+        )
+
+    def test_choices_blank_true_with_default(self):
+        serializer = self.several_choices_serializer()
+        self.assertEqual(
+            serializer.fields['music_genre'].choices,
+            BLANK_CHOICE_DASH + [('rock', 'Rock'), ('metal', 'Metal'), ('grunge', 'Grunge')]
+        )
+
+
 class DepthTest(TestCase):
     def test_implicit_nesting(self):