Allow a custom ordering of headers in CSVRenderer

Enabled by the code from @robguttman in pull request #3

Author: mjumbewu

rest_framework_csv/renderers.py

@@ -12,6 +12,7 @@ class CSVRenderer(BaseRenderer):
     media_type = 'text/csv'
     format = 'csv'
     level_sep = '.'
+    headers = None
 
     def render(self, data, media_type=None, renderer_context=None):
         """
@@ -43,6 +44,7 @@ def tablize(self, data):
             # each item designates the name of the column that the item will
             # fall into.
             data = self.flatten_data(data)
+            data.header = data.header or self.headers
 
             # Get the set of all unique headers, and sort them (unless already provided).
             if not data.header:
@@ -127,4 +129,4 @@ def flatten_dict(self, d):
 
 
 class CSVRendererWithUnderscores (CSVRenderer):
-    level_sep = '_'
+    level_sep = '_'

rest_framework_csv/tests.py

@@ -77,6 +77,17 @@ def test_render_ordered_rows(self):
         dump = renderer.render(data)
         self.assertEqual(dump, csv_file) # field order should be maintained
 
+    def test_render_subset_of_fields(self):
+        renderer = CSVRenderer()
+        renderer.headers = ['a', 'c.x']
+
+        data = [{'a': 1, 'b': 2},
+                {'b': 3, 'c': {'x': 4, 'y': 5}}]
+        dump = renderer.render(data)
+        self.assertEqual(dump, 'a,c.x\r\n'
+                               '1,\r\n,'
+                               '4\r\n')
+
 
 class TestCSVParser(TestCase):