This is in preparation for extraction into the `incrementalmerkletree`
crate, which is not Sapling-specific and therefore cannot hard-code
the depths of these data structures.
This change makes it possible for wallets using the
`zcash_client_backend::data_api::wallet` module to perform transaction
preparation, including input selection and fee calculation, as an
independent step prior to creating proofs and signatures. This can be
used to improve user experience by making it possible to report the
proposed effects of the transaction to the wallet user (including
privacy implications) prior to authorizing the transaction.
The change selection algorithm has the most useful information for
determining whether or not a note is dust, so this adds a new error case
to `ChangeError` that allows the change selection to report the presence
of input notes without economic value back to its caller.
This adds a set of abstractions that allow wallets to provide
independent strategies for fee estimation and note selection, and
implementations of these strategies that perform these operations in the
same fashion as the existing `spend` and `shield_transparent_funds`
functions.
This required a somewhat hefty rework of the error handling in
zcash_client_backend. It fixes an issue with the error types whereby
callees needed to have a bit too much information about the error
types produced by their callers.
Reflect the updated note selection and error handling in zcash_client_sqlite.
This adds a fee calculation strategy abstraction that can be used to
dynamically compute fees so that the total fees required may be taken
taken into account during note selection, and also removes automatic
change creation from the transaction builder.
Change outputs must now be directly created by the caller by the caller.
This is a necessary prerequisite for permitting fees to adjust based
upon the contents of the transaction being constructed.
The initial implementation of the fee strategy simply uses the current
default fee.
Previously, `shield_transparent_funds` was only shielding funds
associated with the legacy default transparent address. This meant
that transparent funds sent to unified addresses could not reliably
be shielded, as a unified address will frequently be constructed
using a diversifier index greater than zero.
This modifies the `get_transparent_receivers` method to return address
metadata containing the account ID and diversifier index used to derive
each address along with the receiver.
In 47a0d0d2b7 `WalletWriteTransparent` was
merged into `WalletWrite`, including its associated type `UtxoRef`.
However, `shield_transparent_funds` placed a bound on this associated
type that was not moved to `WalletWrite`. This left the generic
parameter `U` unconstrained, which didn't cause a local failure because
the method has no local tests, but was immediately apparent when trying
to use the method in the mobile SDKs.
This modifies `decrypt_and_store_transaction` to check for inputs
to a transaction being decrypted that correspond to utxos known
to our wallet. For each such UTXO found, it is marked spent.
These traits introduce a problem, in that constraints on a method cannot
be conditionally required based upon the presence or absence of a
feature flag. Instead, we make the methods previously introduced by
the removed traits present in all cases on the `WalletRead` and
`WalletWrite` traits, but ensure that their implementations return
an error if the caller attempts to use them in a wallet that has not
been configured with support for transparent inputs functionality.
The currently deprecated implementations of `insert_sent_utxo`,
`insert_sent_note`, `put_sent_utxo` and `put_sent_note` all store to the
same `sent_notes` table internally. Since there's no immediate plan to
change this arrangement, it's better to have a single pair of internal
`insert_sent_output` and `put_sent_output` methods instead.
This updates `shield_transparent_funds` to look up the internal
(change) address for the account specified, and use that as the
destination for shielding transparent funds.
Fixed#614
Kris Nuttycombe
Kris Nuttycombe
Hazel OHearn
Daira Emma Hopwood
Jack Grigg