This adds the `data_api::scanning::spanning_tree` module under
a new `unstable-spanning-tree` feature flag, making it available to
other implementations who want to be able to write their own storage
backends without having to reinvent the spanning tree logic.
This fixes the following bug:
Due to complexities related to non-linear scanning, checkpoints are only
added to the wallet's commitment tree in cases where there are notes
discovered within a scanned block. At present, the `shardtree` API only
makes it possible to add multiple checkpoints of the same tree state
when adding checkpoints at the chain tip, and this functionality is not
used by `zcash_client_backend` because we perform checkpoint insertion
in batches that may contain gaps in the case that multiple blocks
contain no Sapling notes. While it would be possible to fix this by
altering the `shardtree` API to permit explicit insertion of multiple
checkpoints of the same tree state at a given note position, this fix
takes a simpler approach.
Instead of ensuring that a checkpoint exists at every block and
computing the required checkpoint depth directly from the minimum number
of confirmations required when attempting a spend, we alter the
`WalletCommitmentTrees` API to allow internal information of the note
commitment tree to be used to determine this checkpoint depth, given the
minimum number of commitments as an argument. This allows us to select a
usable checkpoint from the sparse checkpoint set that resulted from the
sparse insertion of checkpoints described above.
The intent of this API is to provide a single API which returns in a
single call:
* per-account balances, including pending values
* wallet sync progress
Fixes#865Fixes#900
This also removes the zcash_client_sqlite-specific database
initialization procedures in favor of a standardized approach using the
methods available via the data access API.
The `zcash_client_backend::proto::service::compact_tx_streamer_client`
is now the only module controlled by that feature flag, exposing the
service types for use by parsers.
Prior to the scan-before-sync changes, the wallet was able to assume
that the maximum scanned block height at the time of the spend was
within a few blocks of the chain tip. However, under linear scanning
after the spend-before-sync changes this invariant no longer holds,
resulting in a situation where in linear sync conditions the wallet
could attempt to create transactions with already-past expiry heights.
This change separates the notion of "chain tip" from "max scanned
height", relying upon the `scan_queue` table to maintain the wallet's
view of the consensus chain height and using information from the
`blocks` table only in situations where the latest and/or earliest
scanned height is required.
As part of this change, the `WalletRead` interface is also modified to
disambiguate these concepts.
If `from_height = 0` and `limit > 1`, then the conditional being used to
initialise `continuity_check_metadata` was previously running for every
block, and would therefore panic while processing the block at height 1.
Previously this was not clearly specified, and the implementations in
`zcash_client_sqlite` behaved similarly to when `from_height = None`.
Closeszcash/librustzcash#892.
In general, it is preferable to use globally relevant identifiers where
possible. This PR removes the `WalletRead::TxRef` associated type in
favor of using `TxId` directly for the transaction identifier, and
restricts the use of the `NoteRef` type to those scenarios where the
result of one query is intended to be used directly as the input to
another query.
Closes#834
Jack Grigg
Kris Nuttycombe
Kris Nuttycombe
Andrew Arnott