Add UIDONLY and MESSAGELIMIT response parsing - #2
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Real-world IMAP servers (Dovecot, Cyrus) regularly emit 8-bit bytes in
BODYSTRUCTURE responses — typically MIME filenames in non-UTF-8
encodings like Latin-1 or ISO-8859-9 (e.g. Turkish "Görüntü1.png" from
Outlook). The strict 7-bit ASCII parser rejected these, breaking the
parse of a single bad mail and desyncing the entire bulk fetch
stream.
Two changes:
1. `is_char` now accepts any non-NUL byte instead of only US-ASCII.
Real-world server behavior, and RFC 6855 / IMAP4rev2 (RFC 9051)
formally allow UTF-8 in these positions.
2. The `*_utf8` parser functions (`string_utf8`, `nstring_utf8`,
`astring_utf8`, `quoted_utf8`, `text`) now use
`String::from_utf8_lossy` and return `Cow<'_, str>`, falling back
to lossy decoding when bytes are not valid UTF-8 instead of
failing the entire parse.
Callers that previously wrapped `&str` results in `Cow::Borrowed`
have been simplified to take the `Cow<'_, str>` directly. Tests
updated to match the new return types.
Adds a regression test (`test_body_structure_with_8bit_literal_filename`)
that reproduces the original failure: a BODYSTRUCTURE with
`("name" {8}\r\nGörüntü1)` (Turkish filename in Latin-1) now parses
successfully via lossy decoding.
Bumps [codecov/codecov-action](https://github.com/codecov/codecov-action) from 6 to 7. - [Release notes](https://github.com/codecov/codecov-action/releases) - [Changelog](https://github.com/codecov/codecov-action/blob/main/CHANGELOG.md) - [Commits](codecov/codecov-action@v6...v7) --- updated-dependencies: - dependency-name: codecov/codecov-action dependency-version: '7' dependency-type: direct:production update-type: version-update:semver-major ... Signed-off-by: dependabot[bot] <support@github.com>
Bumps [actions/checkout](https://github.com/actions/checkout) from 6 to 7. - [Release notes](https://github.com/actions/checkout/releases) - [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md) - [Commits](actions/checkout@v6...v7) --- updated-dependencies: - dependency-name: actions/checkout dependency-version: '7' dependency-type: direct:production update-type: version-update:semver-major ... Signed-off-by: dependabot[bot] <support@github.com>
This was referenced Jul 29, 2026
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Summary
Add the parser types needed to use RFC 9586 UIDONLY safely:
UIDFETCHseparately from ordinary sequence-numberFETCH;ENABLED UIDONLYconfirmation through an opt-in parser;UIDREQUIREDandMESSAGELIMITresponse codes; andThe existing
parse_response()behavior forENABLEDremains compatible.Callers that need to distinguish successful ENABLE responses opt into
parse_response_with_enabled().Why
After UIDONLY is enabled, the server sends UIDFETCH instead of ordinary FETCH.
Treating the leading UID as a mutable sequence number makes it impossible for
an async client or archiver to enforce the mode correctly.
This is the parser feature step for rustmailer/bichon#333. The same change is
also under discussion in djc#198.
Dependency
This draft is based on the fork update in #1. Until #1 merges, GitHub will also
show those parent-history commits in this PR; the UIDONLY feature itself is the
single commit
05439a90033d67297892c3fe206b8c4285df3821.Verification
cargo fmt --all -- --checkcargo test --all-features: 103 passedcargo clippy --all-targets -- -D warningsThe downstream async-imap PR pins this exact commit temporarily. That pin
should move to the accepted Rustmailer commit or release before downstream
merges.
Downstream PRs: rustmailer/async-imap#2 and rustmailer/bichon#334.