This was a tricky merge (wallet refactor). Please double check my
changes to CreateTransactionInternal(...) in src/wallet/spend.cpp, and to
SendGenerationTransaction(...) in src/wallet/rpc/elements.cpp.
Lastly, I got all the tests passing, but I'm not certain that the changes
with fixed_change_pos in CreateTransactionInternal were correct.
This merge was a bit tricky, since in Elements the witnesses are not
part of the transaction inputs themselves. This merge should be reviewed
carefully.
Rename `BResult` class to `util::Result` and update the class interface to be
more compatible with `std::optional` and with a full-featured result class
implemented in https://github.com/bitcoin/bitcoin/pull/25665. Motivation for
this change is to update existing `BResult` usages now so they don't have to
change later when more features are added in #25665.
This change makes the following improvements originally implemented in #25665:
- More explicit API. Drops potentially misleading `BResult` constructor that
treats any bilingual string argument as an error. Adds `util::Error`
constructor so it is never ambiguous when a result is being assigned an error
or non-error value.
- Better type compatibility. Supports `util::Result<bilingual_str>` return
values to hold translated messages which are not errors.
- More standard and consistent API. `util::Result` supports most of the same
operators and methods as `std::optional`. `BResult` had a less familiar
interface with `HasRes`/`GetObj`/`ReleaseObj` methods. The Result/Res/Obj
naming was also not internally consistent.
- Better code organization. Puts `src/util/` code in the `util::` namespace so
naming reflects code organization and it is obvious where the class is coming
from. Drops "B" from name because it is undocumented what it stands for
(bilingual?)
- Has unit tests.
The subtract fee from outputs assumes that the leftover input amount
will be dropped to fees. However this only happens if that amount is
less than the cost of change. In the event that it is higher than the
cost of change, the leftover amount will actually become a change
output. To avoid this scenario, force a change type which has a high
cost of change.
Followup to commit "MOVEONLY: CWallet transaction code out of
wallet.cpp/.h" that detaches and renames some CWalletTx methods, making
into them into standalone functions or CWallet methods instead.
There are no changes in behavior and no code changes that aren't purely
mechanical. It just gives spend and receive functions more consistent
names and removes the circular dependencies added by the earlier
MOVEONLY commit.
There are also no comment or documentation changes. Removed comments
from transaction.h are just migrated to spend.h, receive.h, and
wallet.h.
Behavior might have recently changed in #17331 (it is not clear) but not
noticed because there is no test coverage.
This adds test coverage for current subtract from recipient behavior
without changing it.
Co-authored-by: Andrew Chow <achow101-github@achow101.com>
