Fixed #3466 -- Fixed problem with specifyin a 'fields' argument to a JSON serializer. Also added documenation for the 'fields' argument.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@5409 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/core/serializers/json.py

@@ -21,6 +21,8 @@ class Serializer(PythonSerializer):
     Convert a queryset to JSON.
     """
     def end_serialization(self):
+        self.options.pop('stream', None)
+        self.options.pop('fields', None)
         simplejson.dump(self.objects, self.stream, cls=DjangoJSONEncoder, **self.options)
 
     def getvalue(self):

django/core/serializers/pyyaml.py

@@ -18,6 +18,8 @@ class Serializer(PythonSerializer):
     Convert a queryset to YAML.
     """
     def end_serialization(self):
+        self.options.pop('stream', None)
+        self.options.pop('fields', None)
         yaml.dump(self.objects, self.stream, **self.options)
         
     def getvalue(self):

docs/serialization.txt

@@ -44,6 +44,25 @@ This is useful if you want to serialize data directly to a file-like object
 
 .. _HTTPResponse: ../request_response/#httpresponse-objects
 
+Subset of fields
+~~~~~~~~~~~~~~~~
+
+If you only want a subset of fields to be serialized, you can 
+specify a `fields` argument to the serializer::
+
+    from django.core import serializers
+    data = serializers.serialize('xml', SomeModel.objects.all(), fields=('name','size'))
+
+In this example, only the `name` and `size` attributes of each model will
+be serialized. 
+
+.. note::
+
+    Depending on your model, you may find that it is not possible to deserialize
+    a model that only serializes a subset of it's fields. If a serialized object
+    doesn't specify all the fields that are required by a model, the deserializer
+    will not be able to save deserialized instances.
+
 Deserializing data
 ------------------
 
@@ -92,10 +111,15 @@ Django "ships" with a few included serializers:
     ``python``  Translates to and from "simple" Python objects (lists, dicts,
                 strings, etc.).  Not really all that useful on its own, but
                 used as a base for other serializers.
+    
+    ``yaml``    Serializes to YAML (Yet Another Markup Lanuage). This 
+                serializer will only be made available if PyYAML_ is installed.
+                
     ==========  ==============================================================
 
 .. _json: http://json.org/
 .. _simplejson: http://undefined.org/python/#simplejson
+.. _PyYAML: http://www.pyyaml.org/
 
 Notes for specific serialization formats
 ----------------------------------------

tests/modeltests/serializers/models.py

@@ -159,4 +159,8 @@ __test__ = {'API_TESTS':"""
 >>> article.author
 <Author: Agnes>
 
+# Serializer output can be restricted to a subset of fields
+>>> print serializers.serialize("json", Article.objects.all(), fields=('headline','pub_date'))
+[{"pk": "1", "model": "serializers.article", "fields": {"headline": "Just kidding; I love TV poker", "pub_date": "2006-06-16 11:00:00"}}, {"pk": "2", "model": "serializers.article", "fields": {"headline": "Time to reform copyright", "pub_date": "2006-06-16 13:00:00"}}, {"pk": "3", "model": "serializers.article", "fields": {"headline": "Forward references pose no problem", "pub_date": "2006-06-16 15:00:00"}}]
+
 """}

tests/regressiontests/serializers_regress/models.py

@@ -205,3 +205,7 @@ class USStatePKData(models.Model):
 # class XMLPKData(models.Model):
 #     data = models.XMLField(primary_key=True)
 
+class ComplexModel(models.Model):
+    field1 = models.CharField(maxlength=10)
+    field2 = models.CharField(maxlength=10)
+    field3 = models.CharField(maxlength=10)

tests/regressiontests/serializers_regress/tests.py

@@ -9,6 +9,7 @@ forward, backwards and self references.
 
 
 import unittest, datetime
+from cStringIO import StringIO
 
 from django.utils.functional import curry
 from django.core import serializers
@@ -278,5 +279,41 @@ def serializerTest(format, self):
     for (func, pk, klass, datum) in test_data:
         func[1](self, pk, klass, datum)
 
+def fieldsTest(format, self):
+    # Clear the database first
+    management.flush(verbosity=0, interactive=False)
+
+    obj = ComplexModel(field1='first',field2='second',field3='third')
+    obj.save()
+    
+    # Serialize then deserialize the test database
+    serialized_data = serializers.serialize(format, [obj], indent=2, fields=('field1','field3'))
+    result = serializers.deserialize(format, serialized_data).next()
+    
+    # Check that the deserialized object contains data in only the serialized fields.
+    self.assertEqual(result.object.field1, 'first')
+    self.assertEqual(result.object.field2, '')
+    self.assertEqual(result.object.field3, 'third')
+
+def streamTest(format, self):
+    # Clear the database first
+    management.flush(verbosity=0, interactive=False)
+
+    obj = ComplexModel(field1='first',field2='second',field3='third')
+    obj.save()
+    
+    # Serialize the test database to a stream
+    stream = StringIO()    
+    serializers.serialize(format, [obj], indent=2, stream=stream)
+    
+    # Serialize normally for a comparison
+    string_data = serializers.serialize(format, [obj], indent=2)
+
+    # Check that the two are the same
+    self.assertEqual(string_data, stream.buffer())
+    stream.close()
+    
 for format in serializers.get_serializer_formats():
     setattr(SerializerTests, 'test_'+format+'_serializer', curry(serializerTest, format))
+    setattr(SerializerTests, 'test_'+format+'_serializer_fields', curry(fieldsTest, format))
+    setattr(SerializerTests, 'test_'+format+'_serializer_stream', curry(fieldsTest, format))