feat: implement StateTransitionJsonConvert and fix PlatformAddress map key serialization

[Copilot]

Problem

StateTransition enum lacked StateTransitionJsonConvert implementation, forcing manual variant matching. Additionally, JSON serialization failed for address-based state transitions containing BTreeMap<PlatformAddress, V> with error "key must be a string" because PlatformAddress (enum with data) serializes as a complex object, violating JSON's string-key requirement.

Investigation revealed both serde_json::to_string_pretty() and to_json() fail identically since to_json() uses platform_value::to_value() internally, which relies on serde.

Changes

StateTransition trait implementations:

• Created json_conversion.rs - dispatches to_json() to variant implementations
• Created value_conversion.rs - dispatches conversion methods to variants
• Implemented StateTransitionFieldTypes returning empty vectors (paths are variant-specific)
• Added state-transition-json-conversion to dash-sdk-features

PlatformAddress map key serialization fix:

• Created platform_address_map_serde.rs - custom serde helpers that serialize PlatformAddress keys as Display strings ("P2PKH(hex...)") and deserialize via FromStr
• Applied to all transitions with BTreeMap<PlatformAddress, ...>:
  • AddressFundsTransferTransitionV0 (inputs, outputs)
  • AddressFundingFromAssetLockTransitionV0 (inputs, outputs)
  • AddressCreditWithdrawalTransitionV0 (inputs)
  • IdentityTopUpFromAddressesTransitionV0 (inputs)
  • IdentityCreateFromAddressesTransitionV0 (inputs)
  • IdentityCreditTransferToAddressesTransitionV0 (recipient_addresses)

WASM bindings update:

• Added state-transition-json-conversion feature to wasm-dpp2 Cargo.toml to maintain feature parity with wasm-dpp

Result

Both serialization paths now work:

// Serde (now works)
let json = serde_json::to_string_pretty(&state_transition)?;

// Custom (now works)
let json = state_transition.to_json(JsonStateTransitionSerializationOptions::default())?;

{
  "inputs": {
    "P2PKH(0101010101010101010101010101010101010101)": [1, 1000]
  }
}

Original prompt

---

This section details on the original issue you should resolve

<issue_title>feat: implement StateTransitionJsonConvert for top-level StateTransition enum</issue_title>
<issue_description>## Problem

In packages/rs-dpp/src/state_transition/mod.rs, the StateTransition enum derives Serialize (behind state-transition-serde-conversion feature), but serde_json::to_string_pretty(&state_transition) fails with "key must be a string" for any variant that contains BTreeMap<PlatformAddress, ...> (e.g. AddressFundsTransfer, AddressFundingFromAssetLock, AddressCreditWithdrawal, IdentityCreateFromAddresses, IdentityTopUpFromAddresses, IdentityCreditTransferToAddresses).

This happens because PlatformAddress is an enum that serializes as a complex structure, not a string, and JSON requires all object keys to be strings.

Every individual variant type already implements StateTransitionJsonConvert (which has a to_json() method that properly converts through platform_value::Value, stringifying identifiers and binary data). But the top-level StateTransition enum itself does NOT implement it, forcing consumers to match on all 15 variants manually.

Proposed Fix

Add an impl StateTransitionJsonConvert<'_> for StateTransition that dispatches to each variant's to_json(). This should go in a new file packages/rs-dpp/src/state_transition/json_conversion.rs (gated behind #[cfg(feature = "state-transition-json-conversion")]), similar to how value_conversion.rs or other dispatch files are structured. The implementation:

#[cfg(feature = "state-transition-json-conversion")]
impl StateTransitionJsonConvert<'_> for StateTransition {
    fn to_json(
        &self,
        options: JsonStateTransitionSerializationOptions,
    ) -> Result<serde_json::Value, ProtocolError> {
        match self {
            StateTransition::DataContractCreate(st) => st.to_json(options),
            StateTransition::DataContractUpdate(st) => st.to_json(options),
            StateTransition::Batch(st) => st.to_json(options),
            StateTransition::IdentityCreate(st) => st.to_json(options),
            StateTransition::IdentityTopUp(st) => st.to_json(options),
            StateTransition::IdentityCreditWithdrawal(st) => st.to_json(options),
            StateTransition::IdentityUpdate(st) => st.to_json(options),
            StateTransition::IdentityCreditTransfer(st) => st.to_json(options),
            StateTransition::MasternodeVote(st) => st.to_json(options),
            StateTransition::IdentityCreditTransferToAddresses(st) => st.to_json(options),
            StateTransition::IdentityCreateFromAddresses(st) => st.to_json(options),
            StateTransition::IdentityTopUpFromAddresses(st) => st.to_json(options),
            StateTransition::AddressFundsTransfer(st) => st.to_json(options),
            StateTransition::AddressFundingFromAssetLock(st) => st.to_json(options),
            StateTransition::AddressCreditWithdrawal(st) => st.to_json(options),
        }
    }
}

Note: StateTransitionJsonConvert has a blanket default to_json() that calls self.to_object() (from StateTransitionValueConvert). Since StateTransitionValueConvert is also not implemented for the top-level enum, the explicit override above is needed. It may also make sense to implement StateTransitionValueConvert for StateTransition with the same dispatch pattern.

Also consider adding state-transition-json-conversion to the dash-sdk-features list in packages/rs-dpp/Cargo.toml so SDK consumers get it by default.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes feat: implement StateTransitionJsonConvert for top-level StateTransition enum #3109

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

[shumkov]

Please update wasm-dpp2 as well then

[lklimek]

@copilot Please update wasm-dpp2 to match changes in this PR.

[Copilot]

Please update wasm-dpp2 as well then

Updated in commit 314a1c6. Added state-transition-json-conversion feature to wasm-dpp2 Cargo.toml to match wasm-dpp.

@copilot Please update wasm-dpp2 to match changes in this PR.

Done in commit 314a1c6. Added state-transition-json-conversion feature to wasm-dpp2/Cargo.toml dependencies.

[lklimek]

Merge Base Report — v3.1-dev → copilot/fix-state-transition-json-conversion

Merge commit: fafac36d43
Risk Factor: 45%

Conflicts Resolved

File	Ours	Theirs	Resolution
rs-dpp/Cargo.toml (dash-sdk-features)	4 separate features: data-contract-json-conversion, identity-value-conversion, state-transition-value-conversion, state-transition-json-conversion	Single unified json-conversion	Theirs — unified feature subsumes all separate ones
identity_credit_transfer_to_addresses/v0/mod.rs	feature = "state-transition-serde-conversion" + custom platform_address_map_serde	feature = "json-conversion" + centralized json_safe_generic_u64_value_map	Theirs — upstream provides a better generalized serializer
wasm-dpp2/Cargo.toml	Many separate features + custom ones	Unified json-conversion + minimal features	Theirs — unified feature covers everything

Safe Changes

• rs-dpp/Cargo.toml — Unified json-conversion correctly subsumes all old per-type features. Old feature names still exist as aliases, so existing #[cfg] guards still compile.
• wasm-dpp2/Cargo.toml — Slimmed to unified json-conversion. Covers all previously separate features.
• identity_credit_transfer_to_addresses/v0/mod.rs — Now uses upstream's centralized json_safe_generic_u64_value_map serializer. Functionally equivalent for BTreeMap<PlatformAddress, Credits>.
• 628 auto-merged upstream files — Disjoint from this PR's 15-file change set. No textual overlap.

⚠️ Changes Requiring Attention

• Inconsistent serde approach — Custom platform_address_map_serde is still used in 7 locations across address_funds and identity transitions (topup_from_addresses, create_from_addresses, address_credit_withdrawal, address_funding_from_asset_lock, address_funds_transfer). Only identity_credit_transfer_to_addresses was switched to the upstream serializer. Same data type (BTreeMap<PlatformAddress, _>) serialized two different ways depending on which transition.

• Stale feature guards — json_conversion.rs and value_conversion.rs still use #[cfg(feature = "state-transition-json-conversion")] / #[cfg(feature = "state-transition-value-conversion")]. These work today (aliases exist in Cargo.toml), but diverge from the upstream convention of using json-conversion / value-conversion directly.

Recommended Follow-up

• Migrate remaining platform_address_map_serde usages to json_safe_generic_u64_value_map (7 files)
• Update #[cfg] guards in json_conversion.rs and value_conversion.rs to use unified feature names
• Verify if custom platform_address_map_serde module can be removed after migration
• Run cargo test -p dpp and cargo test -p wasm-dpp2 to confirm no runtime serialization mismatches

Relevant Upstream Contributors

Author	Key Changes
@shumkov	Unified JSON/Object conversion #3167 (root cause of all 3 conflicts), platform address WASM bindings #3147

_{🤖 Co-authored by Claudius the Magnificent AI Agent}

[lklimek]

replaced by #3167

[github-actions]

✅ DashSDKFFI.xcframework built for this PR.

• Workflow run: https://github.com/dashpay/platform/actions/runs/22995278033
• Artifacts: DashSDKFFI.xcframework (folder), DashSDKFFI.xcframework.zip, xc_checksum.txt

SwiftPM (host the zip at a stable URL, then use):

.binaryTarget(
  name: "DashSDKFFI",
  url: "https://your.cdn.example/DashSDKFFI.xcframework.zip",
  checksum: "eff095b277c9589cd3bf250568a3eba514a575fe6e0d12791db5df995a772bf9"
)

Xcode manual integration:

• Download 'DashSDKFFI.xcframework' artifact from the run link above.
• Drag it into your app target (Frameworks, Libraries & Embedded Content) and set Embed & Sign.
• If using the Swift wrapper package, point its binaryTarget to the xcframework location or add the package and place the xcframework at the expected path.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 56.95%. Comparing base (512db4b) to head (fafac36).
⚠️ Report is 5 commits behind head on v3.1-dev.

Additional details and impacted files

@@             Coverage Diff              @@
##           v3.1-dev    #3110      +/-   ##
============================================
+ Coverage     50.39%   56.95%   +6.55%     
============================================
  Files          3089     1955    -1134     
  Lines        219104   158147   -60957     
============================================
- Hits         110426    90069   -20357     
+ Misses       108678    68078   -40600     

Components	Coverage Δ
dpp	∅ <ø> (∅)
drive	42.38% <ø> (-0.13%)	⬇️
drive-abci	79.21% <ø> (-0.03%)	⬇️
sdk	32.13% <ø> (ø)
dapi-client	∅ <ø> (∅)
platform-version	∅ <ø> (∅)
platform-value	∅ <ø> (∅)
platform-wallet	∅ <ø> (∅)
drive-proof-verifier	∅ <ø> (∅)

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