#15925: fix regression: return None for null and non-date strings.

Since the logic for null detection had to move into the _parseaddr
functions, I removed the wrappers from email.utils and just import the
_parseaddr functions directly.

Lib/email/_parseaddr.py

@@ -48,6 +48,8 @@ def parsedate_tz(data):
     Accounts for military timezones.
     """
     res = _parsedate_tz(data)
+    if not res:
+        return
     if res[9] is None:
         res[9] = 0
     return tuple(res)
@@ -62,6 +64,8 @@ def _parsedate_tz(data):
     source timezone really was UTC.
 
     """
+    if not data:
+        return
     data = data.split()
     # The FWS after the comma after the day-of-week is optional, so search and
     # adjust for this.

Lib/email/utils.py

@@ -37,10 +37,7 @@ from email._parseaddr import quote
 from email._parseaddr import AddressList as _AddressList
 from email._parseaddr import mktime_tz
 
-# We need wormarounds for bugs in these methods in older Pythons (see below)
-from email._parseaddr import parsedate as _parsedate
-from email._parseaddr import parsedate_tz as _parsedate_tz
-from email._parseaddr import _parsedate_tz as __parsedate_tz
+from email._parseaddr import parsedate, parsedate_tz, _parsedate_tz
 
 from quopri import decodestring as _qdecode
 
@@ -222,25 +219,8 @@ def make_msgid(idstring=None, domain=None):
     return msgid
 
 
-
-# These functions are in the standalone mimelib version only because they've
-# subsequently been fixed in the latest Python versions.  We use this to worm
-# around broken older Pythons.
-def parsedate(data):
-    if not data:
-        return None
-    return _parsedate(data)
-
-
-def parsedate_tz(data):
-    if not data:
-        return None
-    return _parsedate_tz(data)
-
 def parsedate_to_datetime(data):
-    if not data:
-        return None
-    *dtuple, tz = __parsedate_tz(data)
+    *dtuple, tz = _parsedate_tz(data)
     if tz is None:
         return datetime.datetime(*dtuple[:6])
     return datetime.datetime(*dtuple[:6],

Lib/test/test_email/test_email.py

@@ -2718,8 +2718,17 @@ class TestMiscellaneous(TestEmailBase):
             utils.formatdate(now, localtime=False, usegmt=True),
             time.strftime('%a, %d %b %Y %H:%M:%S GMT', time.gmtime(now)))
 
-    def test_parsedate_none(self):
-        self.assertEqual(utils.parsedate(''), None)
+    # parsedate and parsedate_tz will become deprecated interfaces someday
+    def test_parsedate_returns_None_for_invalid_strings(self):
+        self.assertIsNone(utils.parsedate(''))
+        self.assertIsNone(utils.parsedate_tz(''))
+        self.assertIsNone(utils.parsedate('0'))
+        self.assertIsNone(utils.parsedate_tz('0'))
+        self.assertIsNone(utils.parsedate('A Complete Waste of Time'))
+        self.assertIsNone(utils.parsedate_tz('A Complete Waste of Time'))
+        # Not a part of the spec but, but this has historically worked:
+        self.assertIsNone(utils.parsedate(None))
+        self.assertIsNone(utils.parsedate_tz(None))
 
     def test_parsedate_compact(self):
         # The FWS after the comma is optional

Misc/NEWS

@@ -36,6 +36,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #15925: fixed regression in email.utils.parsedate and parsedate_tz
+  handling of empty and non-date strings.
+
 - Issue #15421: fix an OverflowError in Calendar.itermonthdates() after
   datetime.MAXYEAR.  Patch by Cédric Krier.