accounts/abi/bind/backends: Disallow AdjustTime for non-empty blocks (ethereum#21334)

* accounts/abi/bind/backends: Disallow timeshift for non-empty blocks

* accounts/abi/bind/backends: added tests for adjust time

* accounts/abi/bind/simulated: added comments, fixed test for AdjustTime

* accounts/abi/bind/backends: updated comment

Author: MariusVanDerWijden

accounts/abi/bind/backends/simulated.go

@@ -675,14 +675,16 @@ func (b *SimulatedBackend) SubscribeNewHead(ctx context.Context, ch chan<- *type
 }
 
 // AdjustTime adds a time shift to the simulated clock.
+// It can only be called on empty blocks.
 func (b *SimulatedBackend) AdjustTime(adjustment time.Duration) error {
 	b.mu.Lock()
 	defer b.mu.Unlock()
 
+	if len(b.pendingBlock.Transactions()) != 0 {
+		return errors.New("Could not adjust time on non-empty block")
+	}
+
 	blocks, _ := core.GenerateChain(b.config, b.blockchain.CurrentBlock(), ethash.NewFaker(), b.database, 1, func(number int, block *core.BlockGen) {
-		for _, tx := range b.pendingBlock.Transactions() {
-			block.AddTx(tx)
-		}
 		block.OffsetTime(int64(adjustment.Seconds()))
 	})
 	statedb, _ := b.blockchain.State()

accounts/abi/bind/backends/simulated_test.go

@@ -143,8 +143,7 @@ func TestSimulatedBackend_AdjustTime(t *testing.T) {
 	defer sim.Close()
 
 	prevTime := sim.pendingBlock.Time()
-	err := sim.AdjustTime(time.Second)
-	if err != nil {
+	if err := sim.AdjustTime(time.Second); err != nil {
 		t.Error(err)
 	}
 	newTime := sim.pendingBlock.Time()
@@ -154,6 +153,44 @@ func TestSimulatedBackend_AdjustTime(t *testing.T) {
 	}
 }
 
+func TestNewSimulatedBackend_AdjustTimeFail(t *testing.T) {
+	testAddr := crypto.PubkeyToAddress(testKey.PublicKey)
+	sim := simTestBackend(testAddr)
+	// Create tx and send
+	tx := types.NewTransaction(0, testAddr, big.NewInt(1000), params.TxGas, big.NewInt(1), nil)
+	signedTx, err := types.SignTx(tx, types.HomesteadSigner{}, testKey)
+	if err != nil {
+		t.Errorf("could not sign tx: %v", err)
+	}
+	sim.SendTransaction(context.Background(), signedTx)
+	// AdjustTime should fail on non-empty block
+	if err := sim.AdjustTime(time.Second); err == nil {
+		t.Error("Expected adjust time to error on non-empty block")
+	}
+	sim.Commit()
+
+	prevTime := sim.pendingBlock.Time()
+	if err := sim.AdjustTime(time.Minute); err != nil {
+		t.Error(err)
+	}
+	newTime := sim.pendingBlock.Time()
+	if newTime-prevTime != uint64(time.Minute.Seconds()) {
+		t.Errorf("adjusted time not equal to a minute. prev: %v, new: %v", prevTime, newTime)
+	}
+	// Put a transaction after adjusting time
+	tx2 := types.NewTransaction(1, testAddr, big.NewInt(1000), params.TxGas, big.NewInt(1), nil)
+	signedTx2, err := types.SignTx(tx2, types.HomesteadSigner{}, testKey)
+	if err != nil {
+		t.Errorf("could not sign tx: %v", err)
+	}
+	sim.SendTransaction(context.Background(), signedTx2)
+	sim.Commit()
+	newTime = sim.pendingBlock.Time()
+	if newTime-prevTime >= uint64(time.Minute.Seconds()) {
+		t.Errorf("time adjusted, but shouldn't be: prev: %v, new: %v", prevTime, newTime)
+	}
+}
+
 func TestSimulatedBackend_BalanceAt(t *testing.T) {
 	testAddr := crypto.PubkeyToAddress(testKey.PublicKey)
 	expectedBal := big.NewInt(10000000000)