Enable signing taproot transactions with only non_witness_utxos

[afilini]

Description

Some wallets may only specify the non_witness_utxo for a PSBT input. If that's the case, BDK should still be able to sign.

This was pointed out in the discussion of #734

Changelog notice

• Enable signing taproot transactions that only specify the non_witness_utxo

Checklists

All Submissions:

• I've signed all my commits
• I followed the contribution guidelines
• I ran cargo fmt and cargo clippy before committing

Bugfixes:

• This pull request breaks the existing API
• I've added tests to reproduce the issue which are now passing
• I'm linking the issue being fixed by this PR

[cryptoquick]

Just tried your branch, works great! PSBT got signed and submitted:
https://mempool.space/testnet/tx/a3baffe1ca14ce357b5fb4caa1b753795e65f4ee330f677044bc17ad387775f8
There's definitely a lot more work to do, but it unblocks me for now. Rust won't let me compile using both 0.19 for WASM and your branch since it's from a different source, though.

[danielabrozzoni]

@cryptoquick can you try including these lines in the Cargo.toml, and then updating to the latest bdk:

[target.'cfg(target_arch = "wasm32")'.dependencies]
rand = { version = "^0.6", features = ["wasm-bindgen"] }

I used this workaround in bitcoindevkit/bdk-cli#117 and it seems to work

[danielabrozzoni]

tACK 5e9965f - the code looks good to me, I played around with the test you provided (inspecting the PSBT, adding/removing the witness and non-witness utxos, etc) and everything works as expected.

[cryptoquick]

@cryptoquick can you try including these lines in the Cargo.toml, and then updating to the latest bdk:

[target.'cfg(target_arch = "wasm32")'.dependencies]
rand = { version = "^0.6", features = ["wasm-bindgen"] }

I used this workaround in bitcoindevkit/bdk-cli#117 and it seems to work

Works great, I can use 0.22 in wasm now, thanks!