sweep: account for all script types in craftSweepTx

With this change, transactions created via craftSweepTx will be
standard. Previously, p2wsh/p2pkh scripts passed in via SendCoins would
be weighted as p2wpkh scripts. With a feerate of 1 sat/vbyte,
transactions returned would be non-standard. Luckily, the critical
sweeper subsystem only used p2wpkh scripts so this only affected
callers from the rpcserver.

Also added is an integration test that fails if SendCoins manages
to generate a non-standard transaction. All script types are now
accounted for in getWeightEstimate, which now errors if an unknown
script type is passed in.

sweep/sweeper_test.go

@@ -124,7 +124,6 @@ func createSweeperTestContext(t *testing.T) *sweeperTestContext {
 		timeoutChan: make(chan chan time.Time, 1),
 	}
 
-	var outputScriptCount byte
 	ctx.sweeper = New(&UtxoSweeperConfig{
 		Notifier: notifier,
 		Wallet:   backend,
@@ -137,8 +136,8 @@ func createSweeperTestContext(t *testing.T) *sweeperTestContext {
 		Signer: &mock.DummySigner{},
 		GenSweepScript: func() ([]byte, error) {
 			script := make([]byte, input.P2WPKHSize)
-			script[0] = outputScriptCount
-			outputScriptCount++
+			script[0] = 0
+			script[1] = 20
 			return script, nil
 		},
 		FeeEstimator:     estimator,
@@ -330,7 +329,8 @@ func assertTxSweepsInputs(t *testing.T, sweepTx *wire.MsgTx,
 // NOTE: This assumes that transactions only have one output, as this is the
 // only type of transaction the UtxoSweeper can create at the moment.
 func assertTxFeeRate(t *testing.T, tx *wire.MsgTx,
-	expectedFeeRate chainfee.SatPerKWeight, inputs ...input.Input) {
+	expectedFeeRate chainfee.SatPerKWeight, changePk []byte,
+	inputs ...input.Input) {
 
 	t.Helper()
 
@@ -355,7 +355,9 @@ func assertTxFeeRate(t *testing.T, tx *wire.MsgTx,
 	outputAmt := tx.TxOut[0].Value
 
 	fee := btcutil.Amount(inputAmt - outputAmt)
-	_, estimator := getWeightEstimate(inputs, nil, 0, nil)
+	_, estimator, err := getWeightEstimate(inputs, nil, 0, changePk)
+	require.NoError(t, err)
+
 	txWeight := estimator.weight()
 
 	expectedFee := expectedFeeRate.FeeForWeight(int64(txWeight))
@@ -1092,14 +1094,19 @@ func TestDifferentFeePreferences(t *testing.T) {
 	// transactions to be broadcast in order of high to low fee preference.
 	ctx.tick()
 
+	// Generate the same type of sweep script that was used for weight
+	// estimation.
+	changePk, err := ctx.sweeper.cfg.GenSweepScript()
+	require.NoError(t, err)
+
 	// The first transaction broadcast should be the one spending the higher
 	// fee rate inputs.
 	sweepTx1 := ctx.receiveTx()
-	assertTxFeeRate(t, &sweepTx1, highFeeRate, input1, input2)
+	assertTxFeeRate(t, &sweepTx1, highFeeRate, changePk, input1, input2)
 
 	// The second should be the one spending the lower fee rate inputs.
 	sweepTx2 := ctx.receiveTx()
-	assertTxFeeRate(t, &sweepTx2, lowFeeRate, input3)
+	assertTxFeeRate(t, &sweepTx2, lowFeeRate, changePk, input3)
 
 	// With the transactions broadcast, we'll mine a block to so that the
 	// result is delivered to each respective client.
@@ -1218,10 +1225,15 @@ func TestBumpFeeRBF(t *testing.T) {
 		t.Fatal(err)
 	}
 
+	// Generate the same type of change script used so we can have accurate
+	// weight estimation.
+	changePk, err := ctx.sweeper.cfg.GenSweepScript()
+	require.NoError(t, err)
+
 	// Ensure that a transaction is broadcast with the lower fee preference.
 	ctx.tick()
 	lowFeeTx := ctx.receiveTx()
-	assertTxFeeRate(t, &lowFeeTx, lowFeeRate, &input)
+	assertTxFeeRate(t, &lowFeeTx, lowFeeRate, changePk, &input)
 
 	// We'll then attempt to bump its fee rate.
 	highFeePref := FeePreference{ConfTarget: 6}
@@ -1242,7 +1254,7 @@ func TestBumpFeeRBF(t *testing.T) {
 	// A higher fee rate transaction should be immediately broadcast.
 	ctx.tick()
 	highFeeTx := ctx.receiveTx()
-	assertTxFeeRate(t, &highFeeTx, highFeeRate, &input)
+	assertTxFeeRate(t, &highFeeTx, highFeeRate, changePk, &input)
 
 	// We'll finish our test by mining the sweep transaction.
 	ctx.backend.mine()