Fixed #26717 -- Added Serializer.stream_class to customize the stream.

django/core/serializers/base.py

@@ -59,6 +59,7 @@ class Serializer(object):
     # internal Django use.
     internal_use_only = False
     progress_class = ProgressBar
+    stream_class = six.StringIO
 
     def serialize(self, queryset, **options):
         """
@@ -66,7 +67,7 @@ class Serializer(object):
         """
         self.options = options
 
-        self.stream = options.pop("stream", six.StringIO())
+        self.stream = options.pop("stream", self.stream_class())
         self.selected_fields = options.pop("fields", None)
         self.use_natural_foreign_keys = options.pop('use_natural_foreign_keys', False)
         self.use_natural_primary_keys = options.pop('use_natural_primary_keys', False)

docs/releases/1.11.txt

@@ -192,7 +192,8 @@ Requests and Responses
 Serialization
 ~~~~~~~~~~~~~
 
-* ...
+* The new ``django.core.serializers.base.Serializer.stream_class`` attribute
+  allows subclasses to customize the default stream.
 
 Signals
 ~~~~~~~

tests/serializers/tests.py

@@ -353,6 +353,29 @@ class SerializersTestBase(object):
         self.assertEqual(base_data, proxy_proxy_data.replace('proxy', ''))
 
 
+class SerializerAPITests(SimpleTestCase):
+
+    def test_stream_class(self):
+        class File(object):
+            def __init__(self):
+                self.lines = []
+
+            def write(self, line):
+                self.lines.append(line)
+
+            def getvalue(self):
+                return ''.join(self.lines)
+
+        class Serializer(serializers.json.Serializer):
+            stream_class = File
+
+        serializer = Serializer()
+        data = serializer.serialize([Score(id=1, score=3.4)])
+        self.assertIs(serializer.stream_class, File)
+        self.assertIsInstance(serializer.stream, File)
+        self.assertEqual(data, '[{"model": "serializers.score", "pk": 1, "fields": {"score": 3.4}}]')
+
+
 class SerializersTransactionTestBase(object):
 
     available_apps = ['serializers']