Backend extensions #385
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Backend extensions #385
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…to User This is a preparation for dropping in-library updates dispatching. The goal is to minimize creating Mailbox objects for commands that are not related to the currently selected mailbox thus reserving Mailbox to only represent currently selected mailbox.
It was observed that while using certain approaches to implement stable sequence numbers view work done during mailbox selection and one done on Status call overlaps. In order to avoid complex contracts like "Status is always called immediately after GetMailbox" or requesting backend to do duplicate work both calls are merged so backend implementation can exploit that and do work only once.
This permits backend to send appropriate updates for each connection and maintain per-connection sequence number view correctly.
EXAMINE command has a number of differences from SELECT and implementing some of them requires backend to be aware that EXAMINE command is used. In particular, FETCH should always work as if BODY.PEEK is used instead of BODY. That is, \Seen flag should not be auto-added to messages.
CHECK command is largely unused and is often implemented as a no-op. It is even removed in IMAP4rev2. This commit replaces corresponding method with Poll(). Newly added argument for Poll is reserved for future extensions that may require explicit polling but cannot allow sending EXPUNGE updates.
This is necessary to generate EXISTS update as a result as required
("SHOULD") by RFC 3501 if the current mailbox is selected.
Was accidentally removed when moving CreateMessage. Also it was never present for COPY so it was added there along the way. memory backend is also updated to conform with that and return backend.ErrNoSuchMailbox.
…ions See GH#322 for related discussion. This commit takes a slightly different approach for interface design by using slices of opaque values instead of a struct. This has a number of benefits, notably backend can easily detect that it receives an "option" that it cannot handle while in struct that would not be possible to see new fields. This, however, creates an similar situation but for go-imap. It is believed that it is not a significant issue since we expect many backends and one go-imap :) Interface changes are mostly applied to command affected by RFC 4466 which defines an uniform framework for command extensions. In this design, it is important for go-imap to know the exact set of extensions supported by backend beforehand (e.g. which Options it can handle). SupportedExtensions() is added to accommodate that. For consistency purposes, it should also be used for extensions that can be easily checked using type assertions (e.g. extensions adding brand new commands).
Written as a PoC for extendable backend interface.
linanh
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Jul 7, 2021
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Closing because this is superseded by go-imap v2. |
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This is a proof-of-concept to start some work on #322. See last 2 commits. To demonstrate how it works I implemented server support for UIDPLUS extension and also add it to memory backend.
Based on #374. Will need rebasing to remove duplicate commits.