bpo-27321 Fix email.generator.py to not replace a non-existent header. (GH-18074)

This PR replaces #1977. The reason for the replacement is two-fold.

The fix itself is different is that if the CTE header doesn't exist in the original message, it is inserted. This is important because the new CTE could be quoted-printable whereas the original is implicit 8bit.

Also the tests are different. The test_nonascii_as_string_without_cte test in #1977 doesn't actually test the issue in that it passes without the fix. The test_nonascii_as_string_without_content_type_and_cte test is improved here, and even though it doesn't fail without the fix, it is included for completeness.

Automerge-Triggered-By: @warsaw
This commit is contained in:
Mark Sapiro 2020-10-19 15:49:19 -07:00 committed by GitHub
parent 1438c2ac77
commit bf838227c3
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3 changed files with 42 additions and 1 deletions

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@ -186,7 +186,11 @@ class Generator:
# If we munged the cte, copy the message again and re-fix the CTE.
if munge_cte:
msg = deepcopy(msg)
msg.replace_header('content-transfer-encoding', munge_cte[0])
# Preserve the header order if the CTE header already exists.
if msg.get('content-transfer-encoding') is None:
msg['Content-Transfer-Encoding'] = munge_cte[0]
else:
msg.replace_header('content-transfer-encoding', munge_cte[0])
msg.replace_header('content-type', munge_cte[1])
# Write the headers. First we see if the message object wants to
# handle that itself. If not, we'll do it generically.

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@ -312,6 +312,41 @@ class TestMessageAPI(TestEmailBase):
g.flatten(msg)
self.assertEqual(fullrepr, s.getvalue())
def test_nonascii_as_string_without_cte(self):
m = textwrap.dedent("""\
MIME-Version: 1.0
Content-type: text/plain; charset="iso-8859-1"
Test if non-ascii messages with no Content-Transfer-Encoding set
can be as_string'd:
Föö bär
""")
source = m.encode('iso-8859-1')
expected = textwrap.dedent("""\
MIME-Version: 1.0
Content-type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
Test if non-ascii messages with no Content-Transfer-Encoding set
can be as_string'd:
F=F6=F6 b=E4r
""")
msg = email.message_from_bytes(source)
self.assertEqual(msg.as_string(), expected)
def test_nonascii_as_string_without_content_type_and_cte(self):
m = textwrap.dedent("""\
MIME-Version: 1.0
Test if non-ascii messages with no Content-Type nor
Content-Transfer-Encoding set can be as_string'd:
Föö bär
""")
source = m.encode('iso-8859-1')
expected = source.decode('ascii', 'replace')
msg = email.message_from_bytes(source)
self.assertEqual(msg.as_string(), expected)
def test_as_bytes(self):
msg = self._msgobj('msg_01.txt')
with openfile('msg_01.txt') as fp:

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@ -0,0 +1,2 @@
Fixed KeyError exception when flattening an email to a string attempts to
replace a non-existent Content-Transfer-Encoding header.