gh-144156: Fix email header folding concatenating encoded words

[robsdedude]

• Issue: Missing 'linear-white-space' between encoded-word in RFC2047 header #144156

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[bitdancer]

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

[bitdancer]

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.

[bitdancer]

Suggested change

	.. _RFC 2047: https://www.rfc-editor.org/rfc/rfc2047
	Fix the folding of headers by the :mod:`email` library when :rfc:`2047` encoded words are used. Now whitespace is correctly preserved and also correctly added between adjacent encoded words. The latter property was broken by the fix for gh-92081, which mostly fixed previous failures to preserve whitespace.

Out of curiosity I checked, and according to the changelogs the buggy fix was released in 3.14 alpha 1, 3.13 beta 2 and 3.12.5. Unfortunately the latter is now final. Maybe we should include that in the news item? I'm not sure what the policy is on that.

[robsdedude]

Maybe we should include that in the news item?

I'm all for documenting known issues and shortcomings. However, I doubt people would find this info in the release notes unless they're doing "software archeology", i.e., they already know (roughly) what info they're looking for.

I'm not sure what the policy is on that.

Neither am I. I'm pretty much a first-time contributor 😅

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