Implement noop validator wallet and use it for watchtower staker strategy

arbnode/node.go

@@ -9,6 +9,7 @@ import (
 	"errors"
 	"fmt"
 	"math/big"
+	"strings"
 	"time"
 
 	flag "github.com/spf13/pflag"
@@ -816,28 +817,32 @@ func createNodeImpl(
 			return nil, err
 		}
 		getExtraGas := func() uint64 { return configFetcher.Get().Staker.ExtraGas }
-		var wallet staker.ValidatorWalletInterface
-		if config.Staker.UseSmartContractWallet || txOptsValidator == nil {
-			var existingWalletAddress *common.Address
-			if len(config.Staker.ContractWalletAddress) > 0 {
-				if !common.IsHexAddress(config.Staker.ContractWalletAddress) {
-					log.Error("invalid validator smart contract wallet", "addr", config.Staker.ContractWalletAddress)
-					return nil, errors.New("invalid validator smart contract wallet address")
+		// TODO: factor this out into separate helper, and split rest of node
+		// creation into multiple helpers.
+		var wallet staker.ValidatorWalletInterface = validatorwallet.NewNoOp(l1client)
+		if !strings.EqualFold(config.Staker.Strategy, "watchtower") {
+			if config.Staker.UseSmartContractWallet || txOptsValidator == nil {
+				var existingWalletAddress *common.Address
+				if len(config.Staker.ContractWalletAddress) > 0 {
+					if !common.IsHexAddress(config.Staker.ContractWalletAddress) {
+						log.Error("invalid validator smart contract wallet", "addr", config.Staker.ContractWalletAddress)
+						return nil, errors.New("invalid validator smart contract wallet address")
+					}
+					tmpAddress := common.HexToAddress(config.Staker.ContractWalletAddress)
+					existingWalletAddress = &tmpAddress
+				}
+				wallet, err = validatorwallet.NewContract(dp, existingWalletAddress, deployInfo.ValidatorWalletCreator, deployInfo.Rollup, l1Reader, txOptsValidator, int64(deployInfo.DeployedAt), func(common.Address) {}, getExtraGas)
+				if err != nil {
+					return nil, err
+				}
+			} else {
+				if len(config.Staker.ContractWalletAddress) > 0 {
+					return nil, errors.New("validator contract wallet specified but flag to use a smart contract wallet was not specified")
+				}
+				wallet, err = validatorwallet.NewEOA(dp, deployInfo.Rollup, l1client, txOptsValidator, getExtraGas)
+				if err != nil {
+					return nil, err
 				}
-				tmpAddress := common.HexToAddress(config.Staker.ContractWalletAddress)
-				existingWalletAddress = &tmpAddress
-			}
-			wallet, err = validatorwallet.NewContract(dp, existingWalletAddress, deployInfo.ValidatorWalletCreator, deployInfo.Rollup, l1Reader, txOptsValidator, int64(deployInfo.DeployedAt), func(common.Address) {}, getExtraGas)
-			if err != nil {
-				return nil, err
-			}
-		} else {
-			if len(config.Staker.ContractWalletAddress) > 0 {
-				return nil, errors.New("validator contract wallet specified but flag to use a smart contract wallet was not specified")
-			}
-			wallet, err = validatorwallet.NewEOA(dp, deployInfo.Rollup, l1client, txOptsValidator, getExtraGas)
-			if err != nil {
-				return nil, err
 			}
 		}
 
@@ -851,9 +856,8 @@ func createNodeImpl(
 		if err != nil {
 			return nil, err
 		}
-		if stakerObj.Strategy() != staker.WatchtowerStrategy {
-			err := wallet.Initialize(ctx)
-			if err != nil {
+		if stakerObj.Strategy() == staker.WatchtowerStrategy {
+			if err := wallet.Initialize(ctx); err != nil {
 				return nil, err
 			}
 		}

staker/validatorwallet/noop.go

@@ -0,0 +1,63 @@
+// Copyright 2021-2022, Offchain Labs, Inc.
+// For license information, see https://github.com/nitro/blob/master/LICENSE
+
+package validatorwallet
+
+import (
+	"context"
+	"errors"
+
+	"github.com/ethereum/go-ethereum/accounts/abi/bind"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/offchainlabs/nitro/arbnode/dataposter"
+	"github.com/offchainlabs/nitro/arbutil"
+	"github.com/offchainlabs/nitro/staker/txbuilder"
+)
+
+// NoOp validator wallet is used for watchtower mode.
+type NoOp struct {
+	l1Client arbutil.L1Interface
+}
+
+func NewNoOp(l1Client arbutil.L1Interface) *NoOp {
+	return &NoOp{l1Client: l1Client}
+}
+
+func (*NoOp) Initialize(context.Context) error { return nil }
+
+func (*NoOp) Address() *common.Address { return nil }
+
+func (*NoOp) AddressOrZero() common.Address { return common.Address{} }
+
+func (*NoOp) TxSenderAddress() *common.Address { return nil }
+
+func (*NoOp) From() common.Address { return common.Address{} }
+
+func (*NoOp) ExecuteTransactions(context.Context, *txbuilder.Builder, common.Address) (*types.Transaction, error) {
+	return nil, errors.New("no op validator wallet cannot execute transactions")
+}
+
+func (*NoOp) TimeoutChallenges(ctx context.Context, challenges []uint64) (*types.Transaction, error) {
+	return nil, errors.New("no op validator wallet cannot timeout challenges")
+}
+
+func (n *NoOp) L1Client() arbutil.L1Interface { return n.l1Client }
+
+func (*NoOp) RollupAddress() common.Address { return common.Address{} }
+
+func (*NoOp) ChallengeManagerAddress() common.Address { return common.Address{} }
+
+func (*NoOp) TestTransactions(ctx context.Context, txs []*types.Transaction) error {
+	return nil
+}
+
+func (*NoOp) CanBatchTxs() bool { return false }
+
+func (*NoOp) AuthIfEoa() *bind.TransactOpts { return nil }
+
+func (w *NoOp) Start(ctx context.Context) {}
+
+func (b *NoOp) StopAndWait() {}
+
+func (b *NoOp) DataPoster() *dataposter.DataPoster { return nil }