4c5ceb040cf50d24201903a9200fb23be88d96fb wallet: CreateTransaction(): return out-params as (optional) struct (Sebastian Falbesoner)
c9fdaa5e3ae09b45be6a5c2d4ee6b1e8cef9d8a8 wallet: CreateTransactionInternal(): return out-params as (optional) struct (Sebastian Falbesoner)
Pull request description:
The method `CWallet::CreateTransaction` currently returns several values in the form of out-parameters:
* the actual newly created transaction (`CTransactionRef& tx`)
* its required fee (`CAmount& nFeeRate`)
* the position of the change output (`int& nChangePosInOut`) -- as the name suggests, this is both an in- and out-param
By returning these values in an optional structure (which returns no value a.k.a. `std::nullopt` if an error occured), the interfaces is shorter, cleaner (requested change position is now in-param and can be passed by value) and callers don't have to create dummy variables for results that they are not interested in.
Note that the names of the replaced out-variables were kept in `CreateTransactionInternal` to keep the diff minimal. Also, the fee calculation data (`FeeCalculation& fee_calc_out`) would be another candidate to put into the structure, but `FeeCalculation` is currently an opaque data type in the wallet interface and I think it should stay that way.
As a potential follow-up, I think it would make sense to also do the same refactoring for `CWallet::FundTransaction`, which has a very similar parameter structure.
Suggested by laanwj in https://github.com/bitcoin/bitcoin/pull/20588#issuecomment-739838428.
ACKs for top commit:
achow101:
re-ACK 4c5ceb040cf50d24201903a9200fb23be88d96fb
Xekyo:
ACK 4c5ceb040cf50d24201903a9200fb23be88d96fb
w0xlt:
crACK 4c5ceb040c
Tree-SHA512: 27e5348bbf4f698713002d40c834dcda59c711c93207113e14522fc6d9ae7f4d8edf1ef6d214c5dd62bb52943d342878960ca333728828bf39b645a27d55d524
1ab389b1ba