accounts/abi, ethclient: Allow sending transactions from unlocked accounts via RPC

accounts/abi/bind/backend.go

@@ -88,6 +88,8 @@ type ContractTransactor interface {
 	EstimateGas(ctx context.Context, call ethereum.CallMsg) (usedGas *big.Int, err error)
 	// SendTransaction injects the transaction into the pending pool for execution.
 	SendTransaction(ctx context.Context, tx *types.Transaction) error
+	// SendUnsignedTransaction injects an unsigned transaction into the pending pool for execution.
+	SendUnsignedTransaction(ctx context.Context, tx *types.Transaction, sender common.Address) error
 }
 
 // ContractBackend defines the methods needed to work with contracts on a read-write basis.

accounts/abi/bind/backends/simulated.go

@@ -287,6 +287,28 @@ func (b *SimulatedBackend) SendTransaction(ctx context.Context, tx *types.Transa
 	return nil
 }
 
+// SendUnsignedTransaction updates the pending block to include the given raw transaction.
+// It panics if the transaction is invalid.
+func (b *SimulatedBackend) SendUnsignedTransaction(ctx context.Context, tx *types.Transaction, sender common.Address) error {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	nonce := b.pendingState.GetNonce(sender)
+	if tx.Nonce() != nonce {
+		panic(fmt.Errorf("invalid transaction nonce: got %d, want %d", tx.Nonce(), nonce))
+	}
+
+	blocks, _ := core.GenerateChain(b.config, b.blockchain.CurrentBlock(), b.database, 1, func(number int, block *core.BlockGen) {
+		for _, tx := range b.pendingBlock.Transactions() {
+			block.AddTx(tx)
+		}
+		block.AddTx(tx)
+	})
+	b.pendingBlock = blocks[0]
+	b.pendingState, _ = state.New(b.pendingBlock.Root(), state.NewDatabase(b.database))
+	return nil
+}
+
 // JumpTimeInSeconds adds skip seconds to the clock
 func (b *SimulatedBackend) AdjustTime(adjustment time.Duration) error {
 	b.mu.Lock()

accounts/abi/bind/base.go

@@ -18,7 +18,6 @@ package bind
 
 import (
 	"context"
-	"errors"
 	"fmt"
 	"math/big"
 
@@ -213,16 +212,20 @@ func (c *BoundContract) transact(opts *TransactOpts, contract *common.Address, i
 		rawTx = types.NewTransaction(nonce, c.address, value, gasLimit, gasPrice, input)
 	}
 	if opts.Signer == nil {
-		return nil, errors.New("no signer to authorize the transaction with")
+		if err := c.transactor.SendUnsignedTransaction(ensureContext(opts.Context), rawTx, opts.From); err != nil {
+			return nil, err
+		}
+		return rawTx, nil
+	} else {
+		signedTx, err := opts.Signer(types.HomesteadSigner{}, opts.From, rawTx)
+		if err != nil {
+			return nil, err
+		}
+		if err := c.transactor.SendTransaction(ensureContext(opts.Context), signedTx); err != nil {
+			return nil, err
+		}
+		return signedTx, nil
 	}
-	signedTx, err := opts.Signer(types.HomesteadSigner{}, opts.From, rawTx)
-	if err != nil {
-		return nil, err
-	}
-	if err := c.transactor.SendTransaction(ensureContext(opts.Context), signedTx); err != nil {
-		return nil, err
-	}
-	return signedTx, nil
 }
 
 func ensureContext(ctx context.Context) context.Context {

ethclient/ethclient.go

@@ -476,6 +476,12 @@ func (ec *Client) SendTransaction(ctx context.Context, tx *types.Transaction) er
 	return ec.c.CallContext(ctx, nil, "eth_sendRawTransaction", common.ToHex(data))
 }
 
+// SendUnsignedTransaction injects an unsigned transaction into the pending pool
+// for execution, depending on the RPC server to calculate the signature.
+func (ec *Client) SendUnsignedTransaction(ctx context.Context, tx *types.Transaction, sender common.Address) error {
+	return ec.c.CallContext(ctx, nil, "eth_sendTransaction", toTransactArg(tx, sender))
+}
+
 func toCallArg(msg ethereum.CallMsg) interface{} {
 	arg := map[string]interface{}{
 		"from": msg.From,
@@ -495,3 +501,19 @@ func toCallArg(msg ethereum.CallMsg) interface{} {
 	}
 	return arg
 }
+
+func toTransactArg(tx *types.Transaction, sender common.Address) interface{} {
+	arg := map[string]interface{}{
+		"from":     sender,
+		"to":       tx.To(),
+		"value":    (*hexutil.Big)(tx.Value()),
+		"gas":      (*hexutil.Big)(tx.Gas()),
+		"gasPrice": (*hexutil.Big)(tx.GasPrice()),
+	}
+
+	if len(tx.Data()) > 0 {
+		arg["data"] = hexutil.Bytes(tx.Data())
+	}
+
+	return arg
+}