Merge pull request #721 from guggero/psbt-change-fix
wallet: use constant input source for change calculation
This commit is contained in:
commit
e6d01202cb
2 changed files with 90 additions and 27 deletions
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@ -19,7 +19,9 @@ import (
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// FundPsbt creates a fully populated PSBT packet that contains enough inputs to
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// fund the outputs specified in the passed in packet with the specified fee
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// rate. If there is change left, a change output from the wallet is added.
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// rate. If there is change left, a change output from the wallet is added and
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// the index of the change output is returned. Otherwise no additional output
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// is created and the index -1 is returned.
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//
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// NOTE: If the packet doesn't contain any inputs, coin selection is performed
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// automatically. If the packet does contain any inputs, it is assumed that full
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@ -32,13 +34,13 @@ import (
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// selected/validated inputs by this method. It is in the caller's
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// responsibility to lock the inputs before handing the partial transaction out.
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func (w *Wallet) FundPsbt(packet *psbt.Packet, account uint32,
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feeSatPerKB btcutil.Amount) error {
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feeSatPerKB btcutil.Amount) (int32, error) {
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// Make sure the packet is well formed. We only require there to be at
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// least one output but not necessarily any inputs.
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err := psbt.VerifyInputOutputLen(packet, false, true)
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if err != nil {
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return err
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return 0, err
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}
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txOut := packet.UnsignedTx.TxOut
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@ -53,7 +55,7 @@ func (w *Wallet) FundPsbt(packet *psbt.Packet, account uint32,
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// dust.
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err := txrules.CheckOutput(output, txrules.DefaultRelayFeePerKb)
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if err != nil {
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return err
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return 0, err
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}
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}
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@ -108,7 +110,8 @@ func (w *Wallet) FundPsbt(packet *psbt.Packet, account uint32,
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false,
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)
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if err != nil {
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return fmt.Errorf("error creating funding TX: %v", err)
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return 0, fmt.Errorf("error creating funding TX: %v",
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err)
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}
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// Copy over the inputs now then collect all UTXO information
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@ -118,7 +121,7 @@ func (w *Wallet) FundPsbt(packet *psbt.Packet, account uint32,
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packet.UnsignedTx.TxIn = tx.Tx.TxIn
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err = addInputInfo(tx.Tx.TxIn)
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if err != nil {
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return err
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return 0, err
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}
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// If there are inputs, we need to check if they're sufficient and add
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@ -127,11 +130,18 @@ func (w *Wallet) FundPsbt(packet *psbt.Packet, account uint32,
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// Make sure all inputs provided are actually ours.
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err = addInputInfo(txIn)
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if err != nil {
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return err
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return 0, err
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}
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// We can leverage the fee calculation of the txauthor package
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// if we provide the selected UTXOs as a coin source.
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// if we provide the selected UTXOs as a coin source. We just
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// need to make sure we always return the full list of user-
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// selected UTXOs rather than a subset, otherwise our change
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// amount will be off (in case the user selected multiple UTXOs
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// that are large enough on their own). That's why we use our
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// own static input source creator instead of the more generic
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// makeInputSource() that selects a subset that is "large
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// enough".
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credits := make([]wtxmgr.Credit, len(txIn))
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for idx, in := range txIn {
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utxo := packet.Inputs[idx].WitnessUtxo
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@ -141,13 +151,13 @@ func (w *Wallet) FundPsbt(packet *psbt.Packet, account uint32,
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PkScript: utxo.PkScript,
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}
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}
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inputSource := makeInputSource(credits)
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inputSource := constantInputSource(credits)
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// We also need a change source which needs to be able to insert
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// a new change addresse into the database.
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dbtx, err := w.db.BeginReadWriteTx()
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if err != nil {
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return err
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return 0, err
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}
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_, changeSource := w.addrMgrWithChangeSource(dbtx, account)
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@ -159,24 +169,25 @@ func (w *Wallet) FundPsbt(packet *psbt.Packet, account uint32,
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)
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if err != nil {
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_ = dbtx.Rollback()
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return fmt.Errorf("fee estimation not successful: %v",
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err)
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return 0, fmt.Errorf("fee estimation not successful: "+
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"%v", err)
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}
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// The transaction could be created, let's commit the DB TX to
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// store the change address (if one was created).
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err = dbtx.Commit()
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if err != nil {
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return fmt.Errorf("could not add change address to "+
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return 0, fmt.Errorf("could not add change address to "+
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"database: %v", err)
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}
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}
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// If there is a change output, we need to copy it over to the PSBT now.
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var changeTxOut *wire.TxOut
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if tx.ChangeIndex >= 0 {
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changeTxOut = tx.Tx.TxOut[tx.ChangeIndex]
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packet.UnsignedTx.TxOut = append(
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packet.UnsignedTx.TxOut,
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tx.Tx.TxOut[tx.ChangeIndex],
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packet.UnsignedTx.TxOut, changeTxOut,
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)
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packet.Outputs = append(packet.Outputs, psbt.POutput{})
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}
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@ -186,10 +197,22 @@ func (w *Wallet) FundPsbt(packet *psbt.Packet, account uint32,
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// partial inputs and outputs accordingly.
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err = psbt.InPlaceSort(packet)
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if err != nil {
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return fmt.Errorf("could not sort PSBT: %v", err)
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return 0, fmt.Errorf("could not sort PSBT: %v", err)
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}
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return nil
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// The change output index might have changed after the sorting. We need
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// to find our index again.
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changeIndex := int32(-1)
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if changeTxOut != nil {
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for idx, txOut := range packet.UnsignedTx.TxOut {
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if psbt.TxOutsEqual(changeTxOut, txOut) {
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changeIndex = int32(idx)
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break
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}
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}
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}
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return changeIndex, nil
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}
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// FinalizePsbt expects a partial transaction with all inputs and outputs fully
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@ -303,3 +326,30 @@ func (w *Wallet) FinalizePsbt(packet *psbt.Packet) error {
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return nil
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}
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// constantInputSource creates an input source function that always returns the
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// static set of user-selected UTXOs.
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func constantInputSource(eligible []wtxmgr.Credit) txauthor.InputSource {
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// Current inputs and their total value. These won't change over
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// different invocations as we want our inputs to remain static since
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// they're selected by the user.
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currentTotal := btcutil.Amount(0)
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currentInputs := make([]*wire.TxIn, 0, len(eligible))
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currentScripts := make([][]byte, 0, len(eligible))
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currentInputValues := make([]btcutil.Amount, 0, len(eligible))
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for _, credit := range eligible {
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nextInput := wire.NewTxIn(&credit.OutPoint, nil, nil)
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currentTotal += credit.Amount
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currentInputs = append(currentInputs, nextInput)
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currentScripts = append(currentScripts, credit.PkScript)
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currentInputValues = append(currentInputValues, credit.Amount)
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}
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return func(target btcutil.Amount) (btcutil.Amount, []*wire.TxIn,
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[]btcutil.Amount, [][]byte, error) {
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return currentTotal, currentInputs, currentInputValues,
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currentScripts, nil
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}
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}
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@ -68,6 +68,8 @@ func TestFundPsbt(t *testing.T) {
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feeRateSatPerKB btcutil.Amount
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expectedErr string
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validatePackage bool
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expectedFee int64
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expectedChange int64
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numExpectedInputs int
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}{{
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name: "no outputs provided",
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@ -106,6 +108,8 @@ func TestFundPsbt(t *testing.T) {
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feeRateSatPerKB: 2000, // 2 sat/byte
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expectedErr: "",
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validatePackage: true,
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expectedChange: 1000000 - 150000 - 368,
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expectedFee: 368,
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numExpectedInputs: 1,
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}, {
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name: "two outputs, two inputs",
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@ -136,13 +140,17 @@ func TestFundPsbt(t *testing.T) {
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feeRateSatPerKB: 2000, // 2 sat/byte
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expectedErr: "",
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validatePackage: true,
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expectedFee: 506,
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expectedChange: 2000000 - 150000 - 506,
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numExpectedInputs: 2,
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}}
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for _, tc := range testCases {
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tc := tc
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t.Run(tc.name, func(t *testing.T) {
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err := w.FundPsbt(tc.packet, 0, tc.feeRateSatPerKB)
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changeIndex, err := w.FundPsbt(
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tc.packet, 0, tc.feeRateSatPerKB,
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)
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// Make sure the error is what we expected.
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if err == nil && tc.expectedErr != "" {
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@ -258,9 +266,10 @@ func TestFundPsbt(t *testing.T) {
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}
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p2wkhIndex := -1
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p2wshIndex := -1
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changeIndex := -1
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totalOut := int64(0)
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for idx, txOut := range txOuts {
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script := txOut.PkScript
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totalOut += txOut.Value
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switch {
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case bytes.Equal(script, testScriptP2WKH):
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@ -269,10 +278,12 @@ func TestFundPsbt(t *testing.T) {
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case bytes.Equal(script, testScriptP2WSH):
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p2wshIndex = idx
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default:
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changeIndex = idx
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}
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}
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totalIn := int64(0)
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for _, txIn := range packet.Inputs {
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totalIn += txIn.WitnessUtxo.Value
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}
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// All outputs must be found.
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if p2wkhIndex < 0 || p2wshIndex < 0 || changeIndex < 0 {
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@ -291,15 +302,17 @@ func TestFundPsbt(t *testing.T) {
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txOuts[p2wshIndex].PkScript)
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}
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// Finally, check the change output size and that it
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// belongs to the wallet.
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expectedFee := int64(368)
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expectedChange := 1000000 - 150000 - expectedFee
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if txOuts[changeIndex].Value != expectedChange {
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// Finally, check the change output size and fee.
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fee := totalIn - totalOut
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if fee != tc.expectedFee {
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t.Fatalf("unexpected fee, got %d wanted %d",
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fee, tc.expectedFee)
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}
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if txOuts[changeIndex].Value != tc.expectedChange {
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t.Fatalf("unexpected change output size, got "+
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"%d wanted %d",
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txOuts[changeIndex].Value,
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expectedChange)
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tc.expectedChange)
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}
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})
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}
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