https://github.com/python/cpython/commit/1c4f01a1607220caadc2aa9ad6574715a5918c17 commit: 1c4f01a1607220caadc2aa9ad6574715a5918c17 branch: 3.14 author: Miss Islington (bot) <31488909+miss-isling...@users.noreply.github.com> committer: bitdancer <rdmur...@bitdance.com> date: 2025-06-15T16:02:16-04:00 summary:
[3.14] gh-67022: Document bytes/str inconsistency in email.header.decode_header() and suggest email.headerregistry.HeaderRegistry as a sane alternative (GH-92900) (#135548) gh-67022: Document bytes/str inconsistency in email.header.decode_header() and suggest email.headerregistry.HeaderRegistry as a sane alternative (GH-92900) * gh-67022: Document bytes/str inconsistency in email.header.decode_header() This function's possible return types have been surprising and error-prone for the entirety of its Python 3.x history. It can return either: 1. `typing.List[typing.Tuple[bytes, typing.Optional[str]]]` of length >1 2. or `typing.List[typing.Tuple[str, None]]`, of length exactly 1 This means that any user of this function must be prepared to accept either `bytes` or `str` for the first member of the 2-tuples it returns, which is a very surprising behavior in Python 3.x, particularly given that the second member of the tuple is supposed to represent the charset/encoding of the first member. This patch documents the behavior of this function, and adds test cases to demonstrate it. As discussed in bpo-22833, this cannot be changed in a backwards-compatible way, and some users of this function depend precisely on the existing behavior. Add warnings about obsolescence of 'email.header.decode_header' and 'email.header.make_header' functions. Recommend use of `email.headerregistry.HeaderRegistry` instead, as suggested in https://github.com/python/cpython/pull/92900#discussion_r1112472177 (cherry picked from commit 60181f4ed0e48ff35dc296da6b51473bfc553d16) Co-authored-by: Dan Lenski <dlen...@gmail.com> files: M Doc/library/email.header.rst M Lib/email/header.py M Lib/test/test_email/test_email.py diff --git a/Doc/library/email.header.rst b/Doc/library/email.header.rst index 219fad0d2f6745..c3392a62b8ee79 100644 --- a/Doc/library/email.header.rst +++ b/Doc/library/email.header.rst @@ -178,16 +178,36 @@ The :mod:`email.header` module also provides the following convenient functions. Decode a message header value without converting the character set. The header value is in *header*. - This function returns a list of ``(decoded_string, charset)`` pairs containing - each of the decoded parts of the header. *charset* is ``None`` for non-encoded - parts of the header, otherwise a lower case string containing the name of the - character set specified in the encoded string. + For historical reasons, this function may return either: - Here's an example:: + 1. A list of pairs containing each of the decoded parts of the header, + ``(decoded_bytes, charset)``, where *decoded_bytes* is always an instance of + :class:`bytes`, and *charset* is either: + + - A lower case string containing the name of the character set specified. + + - ``None`` for non-encoded parts of the header. + + 2. A list of length 1 containing a pair ``(string, None)``, where + *string* is always an instance of :class:`str`. + + An :exc:`email.errors.HeaderParseError` may be raised when certain decoding + errors occur (e.g. a base64 decoding exception). + + Here are examples: >>> from email.header import decode_header >>> decode_header('=?iso-8859-1?q?p=F6stal?=') [(b'p\xf6stal', 'iso-8859-1')] + >>> decode_header('unencoded_string') + [('unencoded_string', None)] + >>> decode_header('bar =?utf-8?B?ZsOzbw==?=') + [(b'bar ', None), (b'f\xc3\xb3o', 'utf-8')] + + .. note:: + + This function exists for for backwards compatibility only. For + new code, we recommend using :class:`email.headerregistry.HeaderRegistry`. .. function:: make_header(decoded_seq, maxlinelen=None, header_name=None, continuation_ws=' ') @@ -203,3 +223,7 @@ The :mod:`email.header` module also provides the following convenient functions. :class:`Header` instance. Optional *maxlinelen*, *header_name*, and *continuation_ws* are as in the :class:`Header` constructor. + .. note:: + + This function exists for for backwards compatibility only, and is + not recommended for use in new code. diff --git a/Lib/email/header.py b/Lib/email/header.py index 113a81f41314ec..220a84a7454b21 100644 --- a/Lib/email/header.py +++ b/Lib/email/header.py @@ -59,16 +59,22 @@ def decode_header(header): """Decode a message header value without converting charset. - Returns a list of (string, charset) pairs containing each of the decoded - parts of the header. Charset is None for non-encoded parts of the header, - otherwise a lower-case string containing the name of the character set - specified in the encoded string. + For historical reasons, this function may return either: + + 1. A list of length 1 containing a pair (str, None). + 2. A list of (bytes, charset) pairs containing each of the decoded + parts of the header. Charset is None for non-encoded parts of the header, + otherwise a lower-case string containing the name of the character set + specified in the encoded string. header may be a string that may or may not contain RFC2047 encoded words, or it may be a Header object. An email.errors.HeaderParseError may be raised when certain decoding error occurs (e.g. a base64 decoding exception). + + This function exists for backwards compatibility only. For new code, we + recommend using email.headerregistry.HeaderRegistry instead. """ # If it is a Header object, we can just return the encoded chunks. if hasattr(header, '_chunks'): @@ -161,6 +167,9 @@ def make_header(decoded_seq, maxlinelen=None, header_name=None, This function takes one of those sequence of pairs and returns a Header instance. Optional maxlinelen, header_name, and continuation_ws are as in the Header constructor. + + This function exists for backwards compatibility only, and is not + recommended for use in new code. """ h = Header(maxlinelen=maxlinelen, header_name=header_name, continuation_ws=continuation_ws) diff --git a/Lib/test/test_email/test_email.py b/Lib/test/test_email/test_email.py index 8765d121fd0813..b8116d073a2670 100644 --- a/Lib/test/test_email/test_email.py +++ b/Lib/test/test_email/test_email.py @@ -2568,6 +2568,18 @@ def test_multiline_header(self): self.assertEqual(str(make_header(decode_header(s))), '"Müller T" <t.muel...@xxx.com>') + def test_unencoded_ascii(self): + # bpo-22833/gh-67022: returns [(str, None)] rather than [(bytes, None)] + s = 'header without encoded words' + self.assertEqual(decode_header(s), + [('header without encoded words', None)]) + + def test_unencoded_utf8(self): + # bpo-22833/gh-67022: returns [(str, None)] rather than [(bytes, None)] + s = 'header with unexpected non ASCII caract\xe8res' + self.assertEqual(decode_header(s), + [('header with unexpected non ASCII caract\xe8res', None)]) + # Test the MIMEMessage class class TestMIMEMessage(TestEmailBase): _______________________________________________ Python-checkins mailing list -- python-checkins@python.org To unsubscribe send an email to python-checkins-le...@python.org https://mail.python.org/mailman3//lists/python-checkins.python.org Member address: arch...@mail-archive.com
