Issue #27895: Strengthen the dict reader tests.

Lib/test/test_csv.py

@@ -11,6 +11,8 @@ import gc
 import pickle
 from test import support
 from itertools import permutations
+from textwrap import dedent
+from collections import OrderedDict
 
 class Test_Csv(unittest.TestCase):
     """
@@ -1109,6 +1111,42 @@ class KeyOrderingTest(unittest.TestCase):
         # Final sanity check: were all permutations unique?
         self.assertEqual(len(resultset), 120, "Key ordering: some key permutations not collected (expected 120)")
 
+    def test_ordered_dict_reader(self):
+        data = dedent('''\
+            FirstName,LastName
+            Eric,Idle
+            Graham,Chapman,Over1,Over2
+
+            Under1
+            John,Cleese
+        ''').splitlines()
+
+        self.assertEqual(list(csv.DictReader(data)),
+            [OrderedDict([('FirstName', 'Eric'), ('LastName', 'Idle')]),
+             OrderedDict([('FirstName', 'Graham'), ('LastName', 'Chapman'),
+                          (None, ['Over1', 'Over2'])]),
+             OrderedDict([('FirstName', 'Under1'), ('LastName', None)]),
+             OrderedDict([('FirstName', 'John'), ('LastName', 'Cleese')]),
+            ])
+
+        self.assertEqual(list(csv.DictReader(data, restkey='OtherInfo')),
+            [OrderedDict([('FirstName', 'Eric'), ('LastName', 'Idle')]),
+             OrderedDict([('FirstName', 'Graham'), ('LastName', 'Chapman'),
+                          ('OtherInfo', ['Over1', 'Over2'])]),
+             OrderedDict([('FirstName', 'Under1'), ('LastName', None)]),
+             OrderedDict([('FirstName', 'John'), ('LastName', 'Cleese')]),
+            ])
+
+        del data[0]            # Remove the header row
+        self.assertEqual(list(csv.DictReader(data, fieldnames=['fname', 'lname'])),
+            [OrderedDict([('fname', 'Eric'), ('lname', 'Idle')]),
+             OrderedDict([('fname', 'Graham'), ('lname', 'Chapman'),
+                          (None, ['Over1', 'Over2'])]),
+             OrderedDict([('fname', 'Under1'), ('lname', None)]),
+             OrderedDict([('fname', 'John'), ('lname', 'Cleese')]),
+            ])
+
+
 class MiscTestCase(unittest.TestCase):
     def test__all__(self):
         extra = {'__doc__', '__version__'}