evm, rpc: fix tx log attribute value is not parsable by some client (#615)

* Problem: tx log attribute value not parsable by some client

Closes: #614

Solution:
- encode the value to json string rather than bytes

Apply suggestions from code review

* rm cdc and changelog

Co-authored-by: Federico Kunze Küllmer <31522760+fedekunze@users.noreply.github.com>
Co-authored-by: Federico Kunze <federico.kunze94@gmail.com>

rpc/ethereum/backend/backend.go

@@ -400,7 +400,8 @@ func (e *EVMBackend) GetTransactionLogs(txHash common.Hash) ([]*ethtypes.Log, er
 	if err != nil {
 		return nil, err
 	}
-	return TxLogsFromEvents(e.clientCtx.Codec, tx.TxResult.Events), nil
+
+	return TxLogsFromEvents(tx.TxResult.Events)
 }
 
 // PendingTransactions returns the transactions that are in the transaction pool
@@ -433,7 +434,11 @@ func (e *EVMBackend) GetLogsByHeight(height *int64) ([][]*ethtypes.Log, error) {
 
 	blockLogs := [][]*ethtypes.Log{}
 	for _, txResult := range blockRes.TxsResults {
-		logs := TxLogsFromEvents(e.clientCtx.Codec, txResult.Events)
+		logs, err := TxLogsFromEvents(txResult.Events)
+		if err != nil {
+			return nil, err
+		}
+
 		blockLogs = append(blockLogs, logs)
 	}
 

rpc/ethereum/backend/utils.go

@@ -2,10 +2,10 @@ package backend
 
 import (
 	"bytes"
+	"encoding/json"
 	"errors"
 	"math/big"
 
-	"github.com/cosmos/cosmos-sdk/codec"
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	authtypes "github.com/cosmos/cosmos-sdk/x/auth/types"
 	"github.com/ethereum/go-ethereum/common"
@@ -135,21 +135,25 @@ func (e *EVMBackend) getAccountNonce(accAddr common.Address, pending bool, heigh
 }
 
 // TxLogsFromEvents parses ethereum logs from cosmos events
-func TxLogsFromEvents(codec codec.Codec, events []abci.Event) []*ethtypes.Log {
+func TxLogsFromEvents(events []abci.Event) ([]*ethtypes.Log, error) {
 	logs := make([]*evmtypes.Log, 0)
 	for _, event := range events {
 		if event.Type != evmtypes.EventTypeTxLog {
 			continue
 		}
+
 		for _, attr := range event.Attributes {
 			if !bytes.Equal(attr.Key, []byte(evmtypes.AttributeKeyTxLog)) {
 				continue
 			}
 
 			var log evmtypes.Log
-			codec.MustUnmarshal(attr.Value, &log)
+			if err := json.Unmarshal(attr.Value, &log); err != nil {
+				return nil, err
+			}
+
 			logs = append(logs, &log)
 		}
 	}
-	return evmtypes.LogsToEthereum(logs)
+	return evmtypes.LogsToEthereum(logs), nil
 }