gh-66788: Add the utf-7-imap codec#153149
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Implement the modified UTF-7 encoding used for international IMAP4
mailbox names (RFC 3501, section 5.1.3). It differs from UTF-7:
"&" is the shift character ("&-" encodes a literal "&"), "," replaces
"/" in the Base64 alphabet, and all non-printable-ASCII characters are
Base64-encoded.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Jul 7, 2026
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I like Victor's suggestion of using "utf-7-imap" for this codec.
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Great idea! It doesn't have particular name in RFC 2152, and on Wikipedia it is called mUTF-7, which looks too generic. |
Rename the modified-UTF-7 codec from imap4-utf-7 to utf-7-imap and register the aliases csUTF7IMAP and mUTF-7. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
serhiy-storchaka
changed the title
Convert the parametrized utf-7-imap codec tests to the subTests() decorator. Add round-trip cases for "+", "+-" (literal, unlike in UTF-7) and a "," in the Base64 run, and replace the duplicate decode-error cases with a "&" at the end of the input and an unterminated but otherwise valid Base64 sequence. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
…7-imap Decode the modified Base64 with binascii.a2b_base64() and the modified alphabet directly, instead of base64.b64decode() with altchars. With strict_mode the "/" character (used by standard Base64 but not by the modified alphabet, which uses ",") is now rejected rather than accepted with a DeprecationWarning. Encoding likewise uses binascii.b2a_base64(). Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Add the
utf-7-imapcodec, implementing the modified UTF-7 encoding used for international IMAP4 mailbox names (RFC 3501, section 5.1.3).It differs from UTF-7 (RFC 2152):
&(not+) is the shift character, and&-encodes a literal&;,is used instead of/in the modified Base64 alphabet;&) are represented directly, so all other characters, including other controls, are Base64-encoded.The aliases
csUTF7IMAPandmUTF-7are also registered.This is the codec dependency of gh-49555 (international mailbox names in
imaplib). Automatic encoding/decoding of mailbox names inimaplibitself is a separate question, left for later — modern servers accept raw UTF-8 names viaUTF8=ACCEPT(RFC 6855), and auto-conversion has non-trivial API implications.🤖 Generated with Claude Code