Add support for min_length / max_length keywords

on basic ModelFields

rest_framework/fields.py

@@ -215,8 +215,19 @@ class ModelField(WritableField):
             self.model_field = kwargs.pop('model_field')
         except:
             raise ValueError("ModelField requires 'model_field' kwarg")
+
+        self.min_length = kwargs.pop('min_length',
+                            getattr(self.model_field, 'min_length', None))
+        self.max_length = kwargs.pop('max_length',
+                            getattr(self.model_field, 'max_length', None))
+        
         super(ModelField, self).__init__(*args, **kwargs)
 
+        if self.min_length is not None:
+            self.validators.append(validators.MinLengthValidator(self.min_length))
+        if self.max_length is not None:
+            self.validators.append(validators.MaxLengthValidator(self.max_length))
+
     def from_native(self, value):
         rel = getattr(self.model_field, "rel", None)
         if rel is not None:

rest_framework/tests/models.py

@@ -35,6 +35,13 @@ def foobar():
     return 'foobar'
 
 
+class CustomField(models.CharField):
+
+    def __init__(self, *args, **kwargs):
+        kwargs['max_length'] = 12
+        super(CustomField, self).__init__(*args, **kwargs)
+
+
 class RESTFrameworkModel(models.Model):
     """
     Base for test models that sets app_label, so they play nicely.
@@ -113,6 +120,7 @@ class Comment(RESTFrameworkModel):
 class ActionItem(RESTFrameworkModel):
     title = models.CharField(max_length=200)
     done = models.BooleanField(default=False)
+    info = CustomField(default='---', max_length=12)
 
 
 # Models for reverse relations

rest_framework/tests/serializer.py

@@ -41,6 +41,7 @@ class CommentSerializer(serializers.Serializer):
 
 
 class ActionItemSerializer(serializers.ModelSerializer):
+    
     class Meta:
         model = ActionItem
 
@@ -247,6 +248,15 @@ class ValidationTests(TestCase):
         self.assertEquals(serializer.is_valid(), False)
         self.assertEquals(serializer.errors, {'title': [u'Ensure this value has at most 200 characters (it has 201).']})
 
+    def test_default_modelfield_max_length_exceeded(self):
+        data = {
+            'title': 'Testing "info" field...',
+            'info': 'x' * 13,
+        }
+        serializer = ActionItemSerializer(data=data)
+        self.assertEquals(serializer.is_valid(), False)
+        self.assertEquals(serializer.errors, {'info': [u'Ensure this value has at most 12 characters (it has 13).']})
+
 
 class MetadataTests(TestCase):
     def test_empty(self):