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Assorted IMAP client robustness fixes#118

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mpscholten:codex/imap-robustness
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Assorted IMAP client robustness fixes#118
mpscholten wants to merge 4 commits into
qnikst:masterfrom
mpscholten:codex/imap-robustness

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Stacked on #117#116#115. Part of the series upstreaming the belege.ai fork's IMAP fixes. The diff shows the earlier commits in the stack until they merge; the commit for this PR is "Assorted IMAP client robustness fixes". Merge order: #115#116#117 → this.

A handful of small, independent client fixes (each is a one-liner-to-a-few-liner):

  • PREAUTH greeting. connectStream only accepted an exact * OK; it now also accepts * PREAUTH and matches the greeting status case-insensitively.
  • Multi-step SASL. AUTHENTICATE now loops over + challenge continuations (getAuthResponse), so mechanisms like XOAUTH2 that emit an error continuation before the tagged response complete instead of hanging. The challenge prefix is matched as + rather than + .
  • Literal forms in getResponse. Understands non-synchronising literals ({n+}) and the binary literal prefix (~{n}), not just {n}.
  • NIL body. fetch/fetchPeek/fetchR/fetchRPeek normalize a NIL body to empty.
  • STORE result + labels. storeFull read result flags from the key "FLAG", which never matches the actual FLAGS data item; fixed to "FLAGS", and X-GM-LABELS values are now quoted.
  • escapeLogin. Unified with quoteIMAPString — drops the invalid backslash-escaping of {/} inside a quoted string (only " and \ are quoted-specials).

Tests

New imapRobustnessTest: PREAUTH + lowercase greeting accepted, empty greeting rejected, multi-step XOAUTH2 continuation consumed, login credential quoting, NIL body normalized.

If you'd prefer these split into separate PRs, happy to — grouped here to keep the series short.

Same single pre-existing master failure (append preserves raw crlf message bytes) as the rest of the series; untouched.

🤖 Generated with Claude Code

Adds UIDPLUS extension support so callers can recover the UIDs the
server assigns on APPEND/COPY and target expunges by UID:

  - appendFullUID: like appendFull, returns the APPENDUID response code
  - copyUID / copyUIDs / copyUIDR: UID COPY returning the COPYUID code
  - uidExpunge / uidExpungeR: UID EXPUNGE over a UID set or range

New types AppendUID and CopyUID, the UIDSet alias, and the
APPENDUID/COPYUID/UIDNOTSTICKY status codes with their parsers.
sendCommandWithResponse exposes the tagged ServerResponse so the
response codes can be read. The existing appendFull/copyFull keep their
old signatures by discarding the UID result.

Covered by new parser cases in baseTest and a dedicated imapUIDPlusTest
group exercising the API against scripted server responses.
RFC 3501 keywords, response codes, flag names and status attributes are
case-insensitive, but the parser matched them with case-sensitive
`string`, so any server replying with non-canonical casing (e.g. `ok`,
`* search`, `[uidvalidity ...]`, `\seen`) caused a parse error.

Adds `stringCI`/`charCI` and applies them throughout the response
parser. Along the way the tagged/fatal response handling is factored
into `pWithTaggedOrFatal`, `pDone` is split into
`pRespCode`/`pRespText`/`pStatusCode`, and string parsing is unified
(`pQuotedString`/`pLiteralString`/`pAString`/`pMailboxName`). This also:

  - surfaces an untagged `* BYE` as a fatal response instead of failing
  - accepts an empty `* SEARCH` reply (no matches)
  - accepts a `NIL` hierarchy separator in LIST/LSUB
  - stops `atomChar` from running past CR/LF

Covered by a new caseInsensitiveTest group.
IMAP SEARCH string keys (BCC/BODY/CC/FROM/HEADER/SUBJECT/TEXT/TO/
X-GM-RAW) were interpolated unquoted, so any value containing a space
or special character produced a malformed command. They are now wrapped
with quoteIMAPString.

LARGER/SMALLER wrongly wrapped their octet count in `{}` (the literal
syntax), e.g. `LARGER {100}`; the size is a plain number (`LARGER 100`).

SEARCH now auto-detects non-ASCII text in a query and prepends
`CHARSET UTF-8`, and command bytes are sent UTF-8 encoded
(sendCommandNoResponse) so the non-ASCII bytes survive instead of being
truncated to Latin-1.

Covered by a new imapSearchApiTest group.
A handful of independent fixes to the IMAP client:

  - connectStream accepts a PREAUTH greeting and matches the greeting
    status case-insensitively (was: only exact "* OK")
  - AUTHENTICATE now loops over '+' challenge continuations via
    getAuthResponse, so multi-step SASL mechanisms (e.g. XOAUTH2) that
    emit an error continuation before the tagged reply complete instead
    of stalling; the challenge prefix is matched as "+" not "+ "
  - getResponse understands non-synchronising literals ({n+}) and the
    binary literal prefix (~{n}), not just plain {n}
  - fetch/fetchPeek/fetchR/fetchRPeek normalize a NIL body to empty
  - storeFull reads result flags from the FLAGS key (was "FLAG", which
    never matched) and quotes X-GM-LABELS values
  - escapeLogin is unified with quoteIMAPString (drops the invalid
    backslash-escaping of { and } inside a quoted string)

Covered by a new imapRobustnessTest group.
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