Migrate Rpc.Transaction test to Cardano.Api.Experimental API

[carbolymer]

Summary

The RPC transaction integration test (cardano-testnet/test/.../Rpc/Transaction.hs) currently uses the old Cardano.Api transaction-building API. It should be migrated to the new Cardano.Api.Experimental API to:

• Align with the direction of cardano-api (old API is being deprecated)
• Use ledger-aligned types directly, reducing impedance mismatch
• Serve as a reference example for RPC + experimental API integration

Current old-API patterns to replace

The test currently uses these old-API constructs:

1. Era handling: ConwayEraOnwards/ShelleyBasedEra with convert — replace with Exp.Era (Exp.ConwayEra)
2. TxOut construction: TxOut addr (lovelaceToTxOutValue sbe coin) TxOutDatumNone ReferenceScriptNone — replace with Exp.TxOut (Ledger.mkBasicTxOut ledgerAddr value)
3. TxBodyContent: defaultTxBodyContent sbe with old setters and wrapper types (BuildTxWith, TxFeeExplicit, KeyWitness KeyWitnessForSpending, LedgerProtocolParameters) — replace with Exp.defaultTxBodyContent + experimental setters using direct ledger types
4. Tx creation: createTransactionBody sbe content — replace with Exp.makeUnsignedTx era content
5. Tx signing: signShelleyTransaction sbe txBody [wit0] — replace with Exp.makeKeyWitness era unsignedTx wit0 then Exp.signTx era [] [keyWit] unsignedTx
6. TxId extraction: getTxId $ getTxBody signedTx — replace with Exp.hashTxBody (ledgerTx ^. L.bodyTxL) or equivalent
7. Serialization: serialiseToCBOR signedTx — replace with serialiseToRawBytes (Exp.SignedTx ledgerTx)

Migration plan

Step 1: Update imports

• Add import qualified Cardano.Api.Experimental as Exp
• Add import qualified Cardano.Api.Experimental.Tx as Exp
• Keep Cardano.Api for shared types still needed (address deserialization, TxIn, TxIx, ShelleyWitnessSigningKey, etc.)
• Keep Cardano.Api.Ledger for direct ledger types (Addr, MaryValue, Coin, etc.)

Step 2: Update era handling

• Replace (ceo, eraProxy) = (conwayBasedEra, asType) with era = Exp.ConwayEra
• Derive sbe = Exp.convert era only where testnet infrastructure still requires ShelleyBasedEra (e.g., cardanoNodeEra = AnyShelleyBasedEra sbe)
• Address deserialization can stay as old-API (deserialiseAddress), converting to ledger Addr via toShelleyAddr where needed for tx outputs

Step 3: Update transaction building

Replace old-style TxBodyContent construction:

-- OLD
let content =
      defaultTxBodyContent sbe
        & setTxIns [(txIn0, pure $ KeyWitness KeyWitnessForSpending)]
        & setTxFee (TxFeeExplicit sbe (L.Coin fee))
        & setTxOuts [TxOut addr1 (lovelaceToTxOutValue sbe $ L.Coin amount) TxOutDatumNone ReferenceScriptNone, ...]
        & setTxProtocolParams (pure . pure $ LedgerProtocolParameters pparams)

With experimental-style:

-- NEW
let ledgerAddr0 = toShelleyAddr addr0
    ledgerAddr1 = toShelleyAddr addr1
    mkOut addr coin = Exp.obtainCommonConstraints era $
      Exp.TxOut (Ledger.mkBasicTxOut addr (Ledger.valueFromList coin []))
    content =
      Exp.defaultTxBodyContent
        & Exp.setTxIns [(txIn0, Exp.AnyKeyWitnessPlaceholder)]
        & Exp.setTxFee (L.Coin fee)
        & Exp.setTxOuts [mkOut ledgerAddr1 amount, mkOut ledgerAddr0 change]
        & Exp.setTxProtocolParams (Just pparams)

Step 4: Update transaction creation and signing

-- OLD
txBody <- H.leftFail $ createTransactionBody sbe content
let signedTx = signShelleyTransaction sbe txBody [wit0]

-- NEW
let unsignedTx = Exp.makeUnsignedTx era content
    keyWit = Exp.makeKeyWitness era unsignedTx wit0
    Exp.SignedTx signedLedgerTx = Exp.signTx era [] [keyWit] unsignedTx

Step 5: Update TxId extraction and serialization

-- OLD
txId' <- H.noteShow . getTxId $ getTxBody signedTx
... serialiseToCBOR signedTx

-- NEW  
txId' <- H.noteShow $ Exp.hashTxBody (signedLedgerTx ^. L.bodyTxL)
... serialiseToRawBytes (Exp.SignedTx signedLedgerTx)

Step 6: Verify utxoRpcPParamsToProtocolParams compatibility

utxoRpcPParamsToProtocolParams already takes Era era and returns L.PParams (ShelleyLedgerEra era) (ledger PParams), so it's already compatible with the experimental API. The call site change is minimal — pass era directly instead of convert ceo.

Notes

• The testnet infrastructure (TestnetRuntime, createAndRunTestnet, etc.) still uses AnyShelleyBasedEra, so sbe = Exp.convert era will still be needed for the testnet options. This is not part of this migration scope.
• Address deserialization from RPC responses (deserialiseAddressBs) uses old-API AddressInEra. These can either be kept (with toShelleyAddr conversion) or replaced with direct ledger address deserialization if available.
• The helper functions txoRefToTxIn and deserialiseAddressBs use old-API types (TxIn, SerialiseAddress) and can remain as-is since they're about deserialization, not tx building.
• Reference test for the experimental API pattern: cardano-api/test/cardano-api-test/Test/Cardano/Api/Experimental.hs

Test plan

• Migrate the code following the steps above
• Build successfully with cabal build cardano-testnet-test
• Run the test: TASTY_PATTERN='/RPC Transaction Submit/' cabal test cardano-testnet-test
• Verify the transaction is still submitted and confirmed correctly via RPC