add_change_if_needed() puts all the change into fees when issuing a delegation certificate

[wutzebaer]

Hi i'm trying to build a transaction which stakes to a pool with cardano-serialization-lib.

Sometimes it uses a utxo like this, wich has about 7ada. This should be enough, fee should only be about 0.2 ada.

But instead of returning the ada add_change_if_needed() puts all the change into the fee. The Transaction is valid, but has too much fees.

The output 0 has no tokens: https://cardanoscan.io/transaction/81aceed33f0ff4560579a41cac8355e6e908633f8b5906f21453568064ab4b6a?tab=utxo

Currently i run CoinSelectionStrategyCIP2.RandomImproveMultiAsset in a loop until it selects inputs where add_change_if_needed() results in txBuilder.get_total_output().to_js_value().coin != "0" but it feels buggy.

I'm using

"node_modules/@emurgo/cardano-serialization-lib-browser": {
  "version": "13.2.1",
  "resolved": "https://registry.npmjs.org/@emurgo/cardano-serialization-lib-browser/-/cardano-serialization-lib-browser-13.2.1.tgz",
  "integrity": "sha512-7RfX1gI16Vj2DgCp/ZoXqyLAakWo6+X95ku/rYGbVzuS/1etrlSiJmdbmdm+eYmszMlGQjrtOJQeVLXoj4L/Ag=="
},

Here is a working example:

const txBuilderConfig = TransactionBuilderConfigBuilder.new()
  .fee_algo(LinearFee.new(BigNum.from_str("44"), BigNum.from_str("155381")))
  .coins_per_utxo_byte(BigNum.from_str("34482"))
  .pool_deposit(BigNum.from_str("500000000"))
  .key_deposit(BigNum.from_str("2000000"))
  .max_value_size(5000)
  .max_tx_size(16384)
  .build();

const testTransaction = () => {
  const changeAddressFromWallet =
    "0184b1feb9c705e664caae0e093ddfd6372dc23b93c62eda05cbbe890a072b585b21c3bfd5e01e775504704af98de330ed4d5a16d3e0186805";
  const rawUtxosFromWallet = [
    "8282582081aceed33f0ff4560579a41cac8355e6e908633f8b5906f21453568064ab4b6a00825839018bd0faf6a901fab1ba4f2325d3ece418cc38f8fbcc360a4a897773fd072b585b21c3bfd5e01e775504704af98de330ed4d5a16d3e01868051a006f28ab",
  ];

  // change address
  const changeAddress = Address.from_bytes(
    Buffer.from(changeAddressFromWallet, "hex")
  );

  // parse utxos
  const utxos = rawUtxosFromWallet.map((ru) => {
    return TransactionUnspentOutput.from_bytes(Buffer.from(ru, "hex"));
  });

  // create transaction unspent outputs
  const transactionUnspentOutputs = TransactionUnspentOutputs.new();
  for (const utxo of utxos) {
    transactionUnspentOutputs.add(utxo);
  }

  const txBuilder = TransactionBuilder.new(txBuilderConfig);

  // build delegation certificate
  const poolKeyHash = Ed25519KeyHash.from_bech32("pool180fejev4xgwe2y53ky0pxvgxr3wcvkweu6feq5mdljfzcsmtg6u");
  const rewardAddressHash = "e1072b585b21c3bfd5e01e775504704af98de330ed4d5a16d3e0186805";
  const address = Address.from_bytes(Buffer.from(rewardAddressHash, "hex"));
  const rewardAddress = RewardAddress.from_address(address)!;
  const stakeCredential = rewardAddress.payment_cred();
  const stakeDelegation = StakeDelegation.new(stakeCredential, poolKeyHash);
  const delegationCert = Certificate.new_stake_delegation(stakeDelegation);
  const certificates = Certificates.new();
  certificates.add(delegationCert);

  txBuilder.set_certs(certificates);

  txBuilder.add_inputs_from(
    transactionUnspentOutputs,
    CoinSelectionStrategyCIP2.RandomImproveMultiAsset
  );

  txBuilder.add_change_if_needed(changeAddress);

  console.log(txBuilder.get_fee_if_set()?.to_js_value())
  console.log(txBuilder.get_total_output().to_js_value().coin)

  return txBuilder.build_tx();
};

[wutzebaer]

Turned out my coins_per_utxo_byte() was wrong

had to change it
from 34482
to 4310

cardano-cli query protocol-parameters --mainnet
"utxoCostPerByte": 4310

i think i had it from a very old example