mempool: Accept test mungers for create tickets.

This modifies CreateTicketPurchase to accept a spendable output (instead
of a transaction) as well as munge functions similar to how
CreateSignedTx works and then introduces a new method named
CreateTicketPurchaseFromTx which keeps the existing signature and is
defined in terms of the aforementioned.

This allows the test code to more easily mutate the transactions as
desired prior to them being signed which provides greater flexibility.

internal/mempool/mempool_test.go

@@ -527,40 +527,44 @@ func (p *poolHarness) CreateTx(out spendableOutput) (*dcrutil.Tx, error) {
 	return txns[0], err
 }
 
-// CreateTicketPurchase creates a ticket purchase spending the first output of
-// the provided transaction.
-func (p *poolHarness) CreateTicketPurchase(sourceTx *dcrutil.Tx, cost int64) (*dcrutil.Tx, error) {
+// CreateTicketPurchase creates a ticket purchase from the provided spendable
+// output.
+func (p *poolHarness) CreateTicketPurchase(input spendableOutput, cost int64, mungers ...func(*wire.MsgTx)) (*dcrutil.Tx, error) {
 	ticketFee := singleInputTicketSize
 	ticketPrice := cost
 
 	// Generate the voting rights, commitment, and change scripts of the ticket.
 	voteScriptVer, voteScript := p.payAddr.VotingRightsScript()
 	commitScriptVer, commitScript := p.payAddr.RewardCommitmentScript(
 		ticketPrice+ticketFee, 0, ticketPrice)
-	change := sourceTx.MsgTx().TxOut[0].Value - ticketPrice - ticketFee
+	change := int64(input.amount) - ticketPrice - ticketFee
 	changeScriptVer, changeScript := p.payAddr.StakeChangeScript()
 
 	// Generate the ticket purchase.
 	tx := wire.NewMsgTx()
 	tx.AddTxIn(&wire.TxIn{
 		PreviousOutPoint: wire.OutPoint{
-			Hash:  *sourceTx.Hash(),
+			Hash:  input.outPoint.Hash,
 			Index: 0,
 			Tree:  wire.TxTreeRegular,
 		},
 		Sequence:    wire.MaxTxInSequenceNum,
-		ValueIn:     sourceTx.MsgTx().TxOut[0].Value,
+		ValueIn:     int64(input.amount),
 		BlockHeight: uint32(p.chain.BestHeight()),
 	})
 
 	tx.AddTxOut(newTxOut(ticketPrice, voteScriptVer, voteScript))
 	tx.AddTxOut(newTxOut(0, commitScriptVer, commitScript))
 	tx.AddTxOut(newTxOut(change, changeScriptVer, changeScript))
 
+	// Perform any transaction munging just before signing.
+	for _, f := range mungers {
+		f(tx)
+	}
+
 	// Sign the ticket purchase.
-	sigScript, err := sign.SignatureScript(tx, 0,
-		sourceTx.MsgTx().TxOut[0].PkScript, txscript.SigHashAll, p.signKey,
-		dcrec.STEcdsaSecp256k1, true)
+	sigScript, err := sign.SignatureScript(tx, 0, p.payScript,
+		txscript.SigHashAll, p.signKey, dcrec.STEcdsaSecp256k1, true)
 	if err != nil {
 		return nil, err
 	}
@@ -569,6 +573,13 @@ func (p *poolHarness) CreateTicketPurchase(sourceTx *dcrutil.Tx, cost int64) (*d
 	return dcrutil.NewTx(tx), nil
 }
 
+// CreateTicketPurchaseFromTx creates a ticket purchase spending the first
+// output of the provided transaction.
+func (p *poolHarness) CreateTicketPurchaseFromTx(sourceTx *dcrutil.Tx, cost int64) (*dcrutil.Tx, error) {
+	spend := txOutToSpendableOut(sourceTx, 0, wire.TxTreeRegular)
+	return p.CreateTicketPurchase(spend, cost)
+}
+
 // newVoteScript generates a voting script from the passed VoteBits, for
 // use in a vote.
 func newVoteScript(voteBits stake.VoteBits) ([]byte, error) {
@@ -973,7 +984,7 @@ func TestTicketPurchaseOrphan(t *testing.T) {
 
 	// Create a ticket purchase transaction spending the outputs of the
 	// prior regular transaction.
-	ticket, err := harness.CreateTicketPurchase(tx, 40000)
+	ticket, err := harness.CreateTicketPurchaseFromTx(tx, 40000)
 	if err != nil {
 		t.Fatalf("unable to create ticket purchase transaction %v", err)
 	}
@@ -1047,7 +1058,7 @@ func TestVoteOrphan(t *testing.T) {
 
 	// Create a ticket purchase transaction spending the outputs of the
 	// prior regular transaction.
-	ticket, err := harness.CreateTicketPurchase(tx, 40000)
+	ticket, err := harness.CreateTicketPurchaseFromTx(tx, 40000)
 	if err != nil {
 		t.Fatalf("unable to create ticket purchase transaction: %v", err)
 	}
@@ -1117,7 +1128,7 @@ func TestRevocationOrphan(t *testing.T) {
 
 	// Create a ticket purchase transaction spending the outputs of the
 	// prior regular transaction.
-	ticket, err := harness.CreateTicketPurchase(tx, 40000)
+	ticket, err := harness.CreateTicketPurchaseFromTx(tx, 40000)
 	if err != nil {
 		t.Fatalf("unable to create ticket purchase transaction: %v", err)
 	}
@@ -1863,7 +1874,7 @@ func TestMaxVoteDoubleSpendRejection(t *testing.T) {
 
 	// Create a ticket purchase transaction spending the outputs of the prior
 	// regular transaction.
-	ticket, err := harness.CreateTicketPurchase(tx, 40000)
+	ticket, err := harness.CreateTicketPurchaseFromTx(tx, 40000)
 	if err != nil {
 		t.Fatalf("unable to create ticket purchase transaction: %v", err)
 	}
@@ -1988,7 +1999,7 @@ func TestDuplicateVoteRejection(t *testing.T) {
 
 	// Create a ticket purchase transaction spending the outputs of the prior
 	// regular transaction.
-	ticket, err := harness.CreateTicketPurchase(tx, 40000)
+	ticket, err := harness.CreateTicketPurchaseFromTx(tx, 40000)
 	if err != nil {
 		t.Fatalf("unable to create ticket purchase transaction: %v", err)
 	}
@@ -2186,7 +2197,7 @@ func TestFetchTransaction(t *testing.T) {
 
 	// Create a ticket purchase transaction spending the outputs of the
 	// prior regular transaction.
-	ticket, err := harness.CreateTicketPurchase(tx, 40000)
+	ticket, err := harness.CreateTicketPurchaseFromTx(tx, 40000)
 	if err != nil {
 		t.Fatalf("unable to create ticket purchase transaction %v", err)
 	}
@@ -2248,7 +2259,7 @@ func TestRemoveDoubleSpends(t *testing.T) {
 
 	// Create a ticket purchase transaction spending the outputs of the
 	// base regular transaction.
-	ticket, err := harness.CreateTicketPurchase(baseTx, 40000)
+	ticket, err := harness.CreateTicketPurchaseFromTx(baseTx, 40000)
 	if err != nil {
 		t.Fatalf("unable to create ticket purchase transaction %v", err)
 	}
@@ -2683,7 +2694,7 @@ func TestStagedTransactionHeight(t *testing.T) {
 		spendableOuts[0],
 	}, 1)
 
-	ticket, err := harness.CreateTicketPurchase(txA, 40000)
+	ticket, err := harness.CreateTicketPurchaseFromTx(txA, 40000)
 	if err != nil {
 		t.Fatalf("unable to create ticket purchase transaction %v", err)
 	}