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gh-144156: Fix email header folding concatenating encoded words#144692

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bitdancer merged 14 commits into
python:mainfrom
robsdedude:fix/gh-144156
Feb 19, 2026
Merged

gh-144156: Fix email header folding concatenating encoded words#144692
bitdancer merged 14 commits into
python:mainfrom
robsdedude:fix/gh-144156

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@robsdedude

@robsdedude robsdedude commented Feb 10, 2026 •
edited by bedevere-app Bot
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@bedevere-app bedevere-app Bot mentioned this pull request Feb 10, 2026
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bedevere-app Bot commented Feb 10, 2026

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Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.

@robsdedude robsdedude changed the title gh-144156: Fix email header wrapping omitting white space Feb 10, 2026
@robsdedude robsdedude marked this pull request as ready for review February 11, 2026 13:32
@robsdedude robsdedude requested a review from a team as a code owner February 11, 2026 13:32
@bitdancer

bitdancer commented Feb 11, 2026

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FYI I've been looking at this and will have a review soonish. You are correct that the gh-92281 fix was buggy.

bitdancer
bitdancer requested changes Feb 12, 2026
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Thanks for fixing this!

I edited this review a bunch, so mistake could have crept in to my code suggestions, though I did test them. The randomizer test should catch any transcription errors if nothing else does.

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bedevere-app Bot commented Feb 12, 2026

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A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.

@robsdedude
Fix broken application of news fragment suggestion
a1cfe3c
@robsdedude
Simplify code …
45022be 
Make use of the fact that folder must never produce a line of only WSP.
@robsdedude
Fix related WSP folding bug
ccf399d
@bitdancer

bitdancer commented Feb 18, 2026

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Just the elif change and this will be ready to go.

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@robsdedude robsdedude requested a review from bitdancer February 19, 2026 09:27
Hide details View details @bitdancer bitdancer merged commit 0f7cd55 into python:main Feb 19, 2026
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@bitdancer bitdancer added needs backport to 3.13 bugs and security fixes needs backport to 3.14 bugs and security fixes labels Feb 19, 2026
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miss-islington-app Bot commented Feb 19, 2026

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Thanks @robsdedude for the PR, and @bitdancer for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13.
🐍🍒⛏🤖

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miss-islington-app Bot commented Feb 19, 2026

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Thanks @robsdedude for the PR, and @bitdancer for merging it 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖

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miss-islington-app Bot commented Feb 19, 2026

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Sorry, @robsdedude and @bitdancer, I could not cleanly backport this to 3.13 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 0f7cd5544a4dd1d7cf892c93c661510d619caaa7 3.13

miss-islington pushed a commit to miss-islington/cpython that referenced this pull request Feb 19, 2026
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pythongh-144156: Fix email header folding concatenating encoded words (… …
b7ec168 
…pythonGH-144692)

The fix for pythongh-92081 (pythongh-92281) was unfortunately flawed, and broke whitespace handling for encoded word patterns that had previously been working correctly but had no corresponding tests, unfortunately in a way that made the resulting headers not RFC compliant, in such a way that Yahoo started rejecting the resulting emails.  This fix was released in 3.14 alpha 1, 3.13 beta 2 and 3.12.5.   This PR fixes the original problem in a way that does not break anything, and in fact fixes a small pre-existing bug (a spurious whitespace after the ':' of the header label if the header value is immediately wrapped on to the next line).  (RDM)
(cherry picked from commit 0f7cd55)

Co-authored-by: Robsdedude <dev@rouvenbauer.de>
Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
Co-authored-by: R. David Murray <rdmurray@bitdance.com>
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bedevere-app Bot commented Feb 19, 2026

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GH-145009 is a backport of this pull request to the 3.14 branch.

@bedevere-app bedevere-app Bot removed the needs backport to 3.14 bugs and security fixes label Feb 19, 2026
bitdancer added a commit that referenced this pull request Feb 19, 2026
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[3.14] gh-144156: Fix email header folding concatenating encoded words ( …
1404a4d 
GH-144692) (#145009)

gh-144156: Fix email header folding concatenating encoded words (GH-144692)

The fix for gh-92081 (gh-92281) was unfortunately flawed, and broke whitespace handling for encoded word patterns that had previously been working correctly but had no corresponding tests, unfortunately in a way that made the resulting headers not RFC compliant, in such a way that Yahoo started rejecting the resulting emails.  This fix was released in 3.14 alpha 1, 3.13 beta 2 and 3.12.5.   This PR fixes the original problem in a way that does not break anything, and in fact fixes a small pre-existing bug (a spurious whitespace after the ':' of the header label if the header value is immediately wrapped on to the next line).  (RDM)
(cherry picked from commit 0f7cd55)

Co-authored-by: Robsdedude <dev@rouvenbauer.de>
Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
Co-authored-by: R. David Murray <rdmurray@bitdance.com>
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bedevere-app Bot commented Feb 24, 2026

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GH-145195 is a backport of this pull request to the 3.13 branch.

@bedevere-app bedevere-app Bot removed the needs backport to 3.13 bugs and security fixes label Feb 24, 2026
bitdancer added a commit that referenced this pull request Feb 24, 2026
@bitdancer @robsdedude @blurb-it
[3.13] gh-144156: Fix email header folding concatenating encoded words ( …
a3c0a80 
GH-144692) (#145195)

The fix for gh-92081 (gh-92281) was unfortunately flawed, and broke whitespace handling for encoded word patterns that had previously been working correctly but had no corresponding tests, unfortunately in a way that made the resulting headers not RFC compliant, in such a way that Yahoo started rejecting the resulting emails.  This fix was released in 3.14 alpha 1, 3.13 beta 2 and 3.12.5.   This PR fixes the original problem in a way that does not break anything, and in fact fixes a small pre-existing bug (a spurious whitespace after the ':' of the header label if the header value is immediately wrapped on to the next line).  (RDM)
(cherry picked from commit 0f7cd55)

Co-authored-by: Robsdedude <dev@rouvenbauer.de>
Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
@robsdedude robsdedude deleted the fix/gh-144156 branch February 25, 2026 09:07
@robsdedude robsdedude mentioned this pull request Feb 25, 2026
Merged
brijkapadia pushed a commit to brijkapadia/cpython that referenced this pull request Feb 28, 2026
@robsdedude @blurb-it
@bitdancer @brijkapadia
pythongh-144156: Fix email header folding concatenating encoded words (… …
21ab5a3 
…python#144692)

The fix for pythongh-92081 (pythongh-92281) was unfortunately flawed, and broke whitespace handling for encoded word patterns that had previously been working correctly but had no corresponding tests, unfortunately in a way that made the resulting headers not RFC compliant, in such a way that Yahoo started rejecting the resulting emails.  This fix was released in 3.14 alpha 1, 3.13 beta 2 and 3.12.5.   This PR fixes the original problem in a way that does not break anything, and in fact fixes a small pre-existing bug (a spurious whitespace after the ':' of the header label if the header value is immediately wrapped on to the next line).  (RDM)

Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
Co-authored-by: R. David Murray <rdmurray@bitdance.com>
ljfp pushed a commit to ljfp/cpython that referenced this pull request Apr 25, 2026
@robsdedude @blurb-it
@bitdancer @ljfp
pythongh-144156: Fix email header folding concatenating encoded words (… …
94812d8 
…python#144692)

The fix for pythongh-92081 (pythongh-92281) was unfortunately flawed, and broke whitespace handling for encoded word patterns that had previously been working correctly but had no corresponding tests, unfortunately in a way that made the resulting headers not RFC compliant, in such a way that Yahoo started rejecting the resulting emails.  This fix was released in 3.14 alpha 1, 3.13 beta 2 and 3.12.5.   This PR fixes the original problem in a way that does not break anything, and in fact fixes a small pre-existing bug (a spurious whitespace after the ':' of the header label if the header value is immediately wrapped on to the next line).  (RDM)

Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
Co-authored-by: R. David Murray <rdmurray@bitdance.com>
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