feat: expose detailed try_finalize_psbt outcomes

[reez]

Description

Close #73

This PR keeps the scope to PSBT finalization only:

• add try_finalize_psbt which returns FinalizePsbtOutcome
• report per input outcomes via FinalizeInputOutcome

Notes to the reviewers

This is now additive rather than breaking: Wallet::finalize_psbt still returns bool

Intentionally not included here:

• changing Wallet::sign to return a richer result type
• any broader redesign beyond the PSBT finalization API surface

Changelog notice

• Add Wallet::try_finalize_psbt, which returns FinalizePsbtOutcome and exposes per-input finalization outcomes while preserving the existing Wallet::finalize_psbt API.

Checklists

All Submissions:

• I've signed all my commits
• I followed the contribution guidelines
• I ran just p before pushing

New Features:

• I've added tests for the new feature
• I've added docs for the new feature

[codecov]

Codecov Report

❌ Patch coverage is 96.62921% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.15%. Comparing base (58fe631) to head (72261ce).
⚠️ Report is 5 commits behind head on master.

Files with missing lines	Patch %	Lines
src/types.rs	82.35%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #433      +/-   ##
==========================================
+ Coverage   80.96%   81.15%   +0.19%     
==========================================
  Files          24       24              
  Lines        5489     5552      +63     
  Branches      247      247              
==========================================
+ Hits         4444     4506      +62     
- Misses        968      970       +2     
+ Partials       77       76       -1     

Flag	Coverage Δ
rust	81.15% <96.62%> (+0.19%)	⬆️

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[reez]

Updated per some good feedback from mammal

[ValuedMammal]

I don't think After and Older are doing much good, and would prefer to leave them out of the new implementation if we plan to support try_finalize_psbt into the future.

[notmandatory]

Concept ACK, glad to see this as a non-breaking change.

[reez]

Added four commits as small follow-ups from review feedback from mammal: make finalization cleanup more explicit, preserve opaque PSBT/input metadata, stop the new try_finalize_psbt path from redacting output metadata, and clarify the internal timelock inputs without changing legacy finalize_psbt behavior.

[oleonardolima]

cACK 09d2cd0

[Musab1258]

tACK 09d2cd0

The concept and approach make sense. I fetched the branch and ran the tests locally, and they all pass. The documentation also clearly specifies when to use the finalize_psbt and try_finalize_psbt methods.

[Musab1258]

If outcomes is empty (e.g. a PSBT with no inputs), is_finalized() returns true, since .all() on an empty iterator is true. Is this the intended behavior or worth documenting/guarding against explicitly?

[reez]

I think this is intended since is_finalized() is only answering whether any input failed finalization, so if there are no inputs there is nothing to fail. This also matches the old finalize_psbt behavior where finished started as true and only changed inside the input loop. But that's my take, open to further thoughts

[ValuedMammal]

ACK ec3a683

[ValuedMammal]

cargo +nightly fmt produced a diff, and it wasn't caught by CI

                             let final_script_witness =
                                 (!tmp_input.witness.is_empty()).then_some(tmp_input.witness);

-                            // BIP174 finalization clears input metadata except UTXOs, final scripts,
-                            // and opaque fields the finalizer does not understand.
+                            // BIP174 finalization clears input metadata except UTXOs, final
+                            // scripts, and opaque fields the finalizer
+                            // does not understand.
                             *psbt_input = bitcoin::psbt::Input {
                                 non_witness_utxo: original.non_witness_utxo,
                                 witness_utxo: original.witness_utxo,

[ValuedMammal]

ACK 72261ce