bpo-30681: Support invalid date format or value in email Date header (GH-22090)

I am re-submitting an older PR which was abandoned but is still relevant, #10783 by @timb07.

The issue being solved () is still relevant. The original PR #10783 was closed as
the final request changes were not applied and since abandoned.

In this new PR I have re-used the original patch plus applied both comments from the review, by @maxking and @pganssle.


For reference, here is the original PR description:
In email.utils.parsedate_to_datetime(), a failure to parse the date, or invalid date components (such as hour outside 0..23) raises an exception. Document this behaviour, and add tests to test_email/test_utils.py to confirm this behaviour.

In email.headerregistry.DateHeader.parse(), check when parsedate_to_datetime() raises an exception and add a new defect InvalidDateDefect; preserve the invalid value as the string value of the header, but set the datetime attribute to None.

Add tests to test_email/test_headerregistry.py to confirm this behaviour; also added test to test_email/test_inversion.py to confirm emails with such defective date headers round trip successfully.

This pull request incorporates feedback gratefully received from @bitdancer, @brettcannon, @Mariatta and @warsaw, and replaces the earlier PR #2254.

Automerge-Triggered-By: GH:warsaw

Lib/test/test_email/test_headerregistry.py

@@ -204,6 +204,22 @@ class TestDateHeader(TestHeaderBase):
         self.assertEqual(len(h.defects), 1)
         self.assertIsInstance(h.defects[0], errors.HeaderMissingRequiredValue)
 
+    def test_invalid_date_format(self):
+        s = 'Not a date header'
+        h = self.make_header('date', s)
+        self.assertEqual(h, s)
+        self.assertIsNone(h.datetime)
+        self.assertEqual(len(h.defects), 1)
+        self.assertIsInstance(h.defects[0], errors.InvalidDateDefect)
+
+    def test_invalid_date_value(self):
+        s = 'Tue, 06 Jun 2017 27:39:33 +0600'
+        h = self.make_header('date', s)
+        self.assertEqual(h, s)
+        self.assertIsNone(h.datetime)
+        self.assertEqual(len(h.defects), 1)
+        self.assertIsInstance(h.defects[0], errors.InvalidDateDefect)
+
     def test_datetime_read_only(self):
         h = self.make_header('date', self.datestring)
         with self.assertRaises(AttributeError):

Lib/test/test_email/test_inversion.py

@@ -46,6 +46,14 @@ class TestInversion(TestEmailBase):
             foo
             """),),
 
+        'header_with_invalid_date': (dedent(b"""\
+            Date: Tue, 06 Jun 2017 27:39:33 +0600
+            From: abc@xyz.com
+            Subject: timezones
+
+            How do they work even?
+            """),),
+
             }
 
     payload_params = {

Lib/test/test_email/test_utils.py

@@ -48,6 +48,16 @@ class DateTimeTests(unittest.TestCase):
             utils.parsedate_to_datetime(self.datestring + ' -0000'),
             self.naive_dt)
 
+    def test_parsedate_to_datetime_with_invalid_raises_valueerror(self):
+        invalid_dates = ['',
+                         '0',
+                         'A Complete Waste of Time'
+                         'Tue, 06 Jun 2017 27:39:33 +0600',
+                         'Tue, 06 Jun 2017 07:39:33 +2600',
+                         'Tue, 06 Jun 2017 27:39:33']
+        for dtstr in invalid_dates:
+            with self.subTest(dtstr=dtstr):
+                self.assertRaises(ValueError, utils.parsedate_to_datetime, dtstr)
 
 class LocaltimeTests(unittest.TestCase):