This PR replaces the existing Python-driven sync server with a new one in Rust.
The new server supports both collection and media syncing, and is compatible
with both the new protocol mentioned below, and older clients. A setting has
been added to the preferences screen to point Anki to a local server, and a
similar setting is likely to come to AnkiMobile soon.
Documentation is available here: <https://docs.ankiweb.net/sync-server.html>
In addition to the new server and refactoring, this PR also makes changes to the
sync protocol. The existing sync protocol places payloads and metadata inside a
multipart POST body, which causes a few headaches:
- Legacy clients build the request in a non-deterministic order, meaning the
entire request needs to be scanned to extract the metadata.
- Reqwest's multipart API directly writes the multipart body, without exposing
the resulting stream to us, making it harder to track the progress of the
transfer. We've been relying on a patched version of reqwest for timeouts,
which is a pain to keep up to date.
To address these issues, the metadata is now sent in a HTTP header, with the
data payload sent directly in the body. Instead of the slower gzip, we now
use zstd. The old timeout handling code has been replaced with a new implementation
that wraps the request and response body streams to track progress, allowing us
to drop the git dependencies for reqwest, hyper-timeout and tokio-io-timeout.
The main other change to the protocol is that one-way syncs no longer need to
downgrade the collection to schema 11 prior to sending.
* Add crate snafu
* Replace all inline structs in AnkiError
* Derive Snafu on AnkiError
* Use snafu for card type errors
* Use snafu whatever error for InvalidInput
* Use snafu for NotFoundError and improve message
* Use snafu for FileIoError to attach context
Remove IoError.
Add some context-attaching helpers to replace code returning bare
io::Errors.
* Add more context-attaching io helpers
* Add message, context and backtrace to new snafus
* Utilize error context and backtrace on frontend
* Rename LocalizedError -> BackendError.
* Remove DocumentedError.
* Have all backend exceptions inherit BackendError.
* Rename localized(_description) -> message
* Remove accidentally committed experimental trait
* invalid_input_context -> ok_or_invalid
* ensure_valid_input! -> require!
* Always return `Err` from `invalid_input!`
Instead of a Result to unwrap, the macro accepts a source error now.
* new_tempfile_in_parent -> new_tempfile_in_parent_of
* ok_or_not_found -> or_not_found
* ok_or_invalid -> or_invalid
* Add crate convert_case
* Use unqualified lowercase type name
* Remove uses of snafu::ensure
* Allow public construction of InvalidInputErrors (dae)
Needed to port the AnkiDroid changes.
* Make into_protobuf() public (dae)
Also required for AnkiDroid. Not sure why it worked previously - possible
bug in older Rust version?
