Fix eth events query and sync inconsistent state

- kvdb
	- Fix path in Last when doing `setNew`
	- Only close if db != nil, and after closing, always set db to nil
		- This will avoid a panic in the case where the db is closed but
		  there's an error soon after, and a future call tries to close
		  again.  This is because pebble.Close() will panic if the db is
		  already closed.
	- Avoid calling pebble methods when a the Storage interface already
	  implements that method (like Close).
- statedb
	- In test, avoid calling KVDB method if the same method is available for
	  the StateDB (like MakeCheckpoint, CurrentBatch).
- eth
	- In *EventByBlock methods, take blockHash as input argument and use it
	  when querying the event logs.  Previously the blockHash was only taken
	  from the logs results *only if* there was any log.  This caused the
	  following issue: if there was no logs, it was not possible to know if
	  the result was from the expected block or an uncle block!  By querying
	  logs by blockHash we make sure that even if there are no logs, they
	  are from the right block.
	  	- Note that now the function can either be called with a
		  blockNum or blockHash, but not both at the same time.
- sync
	- If there's an error during call to Sync call resetState, which
	  internally resets the stateDB to avoid stale checkpoints (and a
	  corresponding invalid increase in the StateDB batchNum).
	- During a Sync, after very batch processed, make sure that the StateDB
	  currentBatch corresponds to the batchNum in the smart contract
	  log/event.

eth/wdelayer.go

@@ -134,7 +134,7 @@ type WDelayerInterface interface {
 	WDelayerWithdrawal(owner, token ethCommon.Address) (*types.Transaction, error)
 	WDelayerEscapeHatchWithdrawal(to, token ethCommon.Address, amount *big.Int) (*types.Transaction, error)
 
-	WDelayerEventsByBlock(blockNum int64) (*WDelayerEvents, *ethCommon.Hash, error)
+	WDelayerEventsByBlock(blockNum int64, blockHash *ethCommon.Hash) (*WDelayerEvents, error)
 	WDelayerConstants() (*common.WDelayerConstants, error)
 	WDelayerEventInit() (*WDelayerEventInitialize, int64, error)
 }
@@ -424,40 +424,47 @@ func (c *WDelayerClient) WDelayerEventInit() (*WDelayerEventInitialize, int64, e
 }
 
 // WDelayerEventsByBlock returns the events in a block that happened in the
-// WDelayer Smart Contract and the blockHash where the eents happened.  If
-// there are no events in that block, blockHash is nil.
-func (c *WDelayerClient) WDelayerEventsByBlock(blockNum int64) (*WDelayerEvents, *ethCommon.Hash, error) {
+// WDelayer Smart Contract.
+// To query by blockNum, set blockNum >= 0 and blockHash == nil.
+// To query by blockHash, set blockNum == -1 and blockHash != nil.
+// If there are no events in that block the result is nil.
+func (c *WDelayerClient) WDelayerEventsByBlock(blockNum int64,
+	blockHash *ethCommon.Hash) (*WDelayerEvents, error) {
 	var wdelayerEvents WDelayerEvents
-	var blockHash *ethCommon.Hash
 
+	var blockNumBigInt *big.Int
+	if blockNum >= 0 {
+		blockNumBigInt = big.NewInt(blockNum)
+	}
 	query := ethereum.FilterQuery{
-		FromBlock: big.NewInt(blockNum),
-		ToBlock:   big.NewInt(blockNum),
+		BlockHash: blockHash,
+		FromBlock: blockNumBigInt,
+		ToBlock:   blockNumBigInt,
 		Addresses: []ethCommon.Address{
 			c.address,
 		},
-		BlockHash: nil,
-		Topics:    [][]ethCommon.Hash{},
+		Topics: [][]ethCommon.Hash{},
 	}
 
 	logs, err := c.client.client.FilterLogs(context.Background(), query)
 	if err != nil {
-		return nil, nil, tracerr.Wrap(err)
+		return nil, tracerr.Wrap(err)
 	}
-	if len(logs) > 0 {
-		blockHash = &logs[0].BlockHash
+	if len(logs) == 0 {
+		return nil, nil
 	}
+
 	for _, vLog := range logs {
-		if vLog.BlockHash != *blockHash {
+		if blockHash != nil && vLog.BlockHash != *blockHash {
 			log.Errorw("Block hash mismatch", "expected", blockHash.String(), "got", vLog.BlockHash.String())
-			return nil, nil, tracerr.Wrap(ErrBlockHashMismatchEvent)
+			return nil, tracerr.Wrap(ErrBlockHashMismatchEvent)
 		}
 		switch vLog.Topics[0] {
 		case logWDelayerDeposit:
 			var deposit WDelayerEventDeposit
 			err := c.contractAbi.UnpackIntoInterface(&deposit, "Deposit", vLog.Data)
 			if err != nil {
-				return nil, nil, tracerr.Wrap(err)
+				return nil, tracerr.Wrap(err)
 			}
 			deposit.Owner = ethCommon.BytesToAddress(vLog.Topics[1].Bytes())
 			deposit.Token = ethCommon.BytesToAddress(vLog.Topics[2].Bytes())
@@ -468,7 +475,7 @@ func (c *WDelayerClient) WDelayerEventsByBlock(blockNum int64) (*WDelayerEvents,
 			var withdraw WDelayerEventWithdraw
 			err := c.contractAbi.UnpackIntoInterface(&withdraw, "Withdraw", vLog.Data)
 			if err != nil {
-				return nil, nil, tracerr.Wrap(err)
+				return nil, tracerr.Wrap(err)
 			}
 			withdraw.Token = ethCommon.BytesToAddress(vLog.Topics[1].Bytes())
 			withdraw.Owner = ethCommon.BytesToAddress(vLog.Topics[2].Bytes())
@@ -482,7 +489,7 @@ func (c *WDelayerClient) WDelayerEventsByBlock(blockNum int64) (*WDelayerEvents,
 			var withdrawalDelay WDelayerEventNewWithdrawalDelay
 			err := c.contractAbi.UnpackIntoInterface(&withdrawalDelay, "NewWithdrawalDelay", vLog.Data)
 			if err != nil {
-				return nil, nil, tracerr.Wrap(err)
+				return nil, tracerr.Wrap(err)
 			}
 			wdelayerEvents.NewWithdrawalDelay = append(wdelayerEvents.NewWithdrawalDelay, withdrawalDelay)
 
@@ -490,7 +497,7 @@ func (c *WDelayerClient) WDelayerEventsByBlock(blockNum int64) (*WDelayerEvents,
 			var escapeHatchWithdrawal WDelayerEventEscapeHatchWithdrawal
 			err := c.contractAbi.UnpackIntoInterface(&escapeHatchWithdrawal, "EscapeHatchWithdrawal", vLog.Data)
 			if err != nil {
-				return nil, nil, tracerr.Wrap(err)
+				return nil, tracerr.Wrap(err)
 			}
 			escapeHatchWithdrawal.Who = ethCommon.BytesToAddress(vLog.Topics[1].Bytes())
 			escapeHatchWithdrawal.To = ethCommon.BytesToAddress(vLog.Topics[2].Bytes())
@@ -501,7 +508,7 @@ func (c *WDelayerClient) WDelayerEventsByBlock(blockNum int64) (*WDelayerEvents,
 			var emergencyCouncil WDelayerEventNewEmergencyCouncil
 			err := c.contractAbi.UnpackIntoInterface(&emergencyCouncil, "NewEmergencyCouncil", vLog.Data)
 			if err != nil {
-				return nil, nil, tracerr.Wrap(err)
+				return nil, tracerr.Wrap(err)
 			}
 			wdelayerEvents.NewEmergencyCouncil = append(wdelayerEvents.NewEmergencyCouncil, emergencyCouncil)
 
@@ -509,10 +516,10 @@ func (c *WDelayerClient) WDelayerEventsByBlock(blockNum int64) (*WDelayerEvents,
 			var governanceAddress WDelayerEventNewHermezGovernanceAddress
 			err := c.contractAbi.UnpackIntoInterface(&governanceAddress, "NewHermezGovernanceAddress", vLog.Data)
 			if err != nil {
-				return nil, nil, tracerr.Wrap(err)
+				return nil, tracerr.Wrap(err)
 			}
 			wdelayerEvents.NewHermezGovernanceAddress = append(wdelayerEvents.NewHermezGovernanceAddress, governanceAddress)
 		}
 	}
-	return &wdelayerEvents, blockHash, nil
+	return &wdelayerEvents, nil
 }