[3.13] gh-67022: Document bytes/str inconsistency in email.header.decode_header() and suggest email.headerregistry.HeaderRegistry as a sane alternative (GH-92900)#135549
Merged
bitdancer merged 1 commit intopython:3.13from Jun 15, 2025
Conversation
…de_header() and suggest email.headerregistry.HeaderRegistry as a sane alternative (pythonGH-92900) * pythongh-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 python#92900 (comment) (cherry picked from commit 60181f4) Co-authored-by: Dan Lenski <dlenski@gmail.com>
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
3 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
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:
typing.List[typing.Tuple[bytes, typing.Optional[str]]]of length >1typing.List[typing.Tuple[str, None]], of length exactly 1This means that any user of this function must be prepared to accept either
bytesorstrfor the first member of the 2-tuples it returns, which is avery 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.HeaderRegistryinstead, as suggestedin #92900 (comment)
(cherry picked from commit 60181f4)
Co-authored-by: Dan Lenski dlenski@gmail.com
📚 Documentation preview 📚: https://cpython-previews--135549.org.readthedocs.build/