From 152ebdc18048c7ee577a6f4e0ae7f83d7fe26876 Mon Sep 17 00:00:00 2001
From: HuangYi <huang@crypto.com>
Date: Tue, 14 Dec 2021 15:03:15 +0800
Subject: [PATCH 1/3] Problem: empty topics shouldn't be encoded as nil

Closes: #839

Solution:
- encode it as empty array
---
 x/evm/types/logs.go | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/x/evm/types/logs.go b/x/evm/types/logs.go
index 75cea38896..4cf73c94dc 100644
--- a/x/evm/types/logs.go
+++ b/x/evm/types/logs.go
@@ -70,9 +70,9 @@ func (log *Log) Validate() error {
 
 // ToEthereum returns the Ethereum type Log from a Ethermint proto compatible Log.
 func (log *Log) ToEthereum() *ethtypes.Log {
-	var topics []common.Hash // nolint: prealloc
-	for i := range log.Topics {
-		topics = append(topics, common.HexToHash(log.Topics[i]))
+	topics := make([]common.Hash, len(log.Topics))
+	for i, topic := range log.Topics {
+		topics[i] = common.HexToHash(topic)
 	}
 
 	return &ethtypes.Log{
@@ -108,9 +108,9 @@ func LogsToEthereum(logs []*Log) []*ethtypes.Log {
 
 // NewLogFromEth creates a new Log instance from a Ethereum type Log.
 func NewLogFromEth(log *ethtypes.Log) *Log {
-	var topics []string // nolint: prealloc
-	for _, topic := range log.Topics {
-		topics = append(topics, topic.String())
+	topics := make([]string, len(log.Topics))
+	for i, topic := range log.Topics {
+		topics[i] = topic.String()
 	}
 
 	return &Log{

From cb7c3d7c99a6d9592f3b75314e67dd7d00cdee9c Mon Sep 17 00:00:00 2001
From: HuangYi <huang@crypto.com>
Date: Tue, 14 Dec 2021 15:45:18 +0800
Subject: [PATCH 2/3] fix unit tests

---
 x/evm/keeper/statedb_test.go | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/x/evm/keeper/statedb_test.go b/x/evm/keeper/statedb_test.go
index 7c69072b45..a3cb8cafdf 100644
--- a/x/evm/keeper/statedb_test.go
+++ b/x/evm/keeper/statedb_test.go
@@ -592,6 +592,7 @@ func (suite *KeeperTestSuite) TestAddLog() {
 			&ethtypes.Log{
 				Address: addr,
 				TxHash:  txHash,
+				Topics:  make([]common.Hash, 0),
 			},
 			func() {},
 		},
@@ -606,6 +607,7 @@ func (suite *KeeperTestSuite) TestAddLog() {
 				TxHash:  txHash2,
 				TxIndex: 1,
 				Index:   1,
+				Topics:  make([]common.Hash, 0),
 			},
 			func() {
 				suite.app.EvmKeeper.SetTxHashTransient(txHash)
@@ -624,6 +626,7 @@ func (suite *KeeperTestSuite) TestAddLog() {
 			&ethtypes.Log{
 				Address: addr,
 				TxHash:  txHash3,
+				Topics:  make([]common.Hash, 0),
 			},
 			func() {},
 		},
@@ -638,6 +641,7 @@ func (suite *KeeperTestSuite) TestAddLog() {
 				TxHash:  txHash4,
 				TxIndex: 1,
 				Index:   1,
+				Topics:  make([]common.Hash, 0),
 			},
 			func() {
 				suite.app.EvmKeeper.SetTxHashTransient(txHash)

From 42b3a14f6c30388c34dcd271c2511af478151786 Mon Sep 17 00:00:00 2001
From: HuangYi <huang@crypto.com>
Date: Tue, 14 Dec 2021 20:44:39 +0800
Subject: [PATCH 3/3] changelog

---
 CHANGELOG.md | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index b39a9c52e3..77ef6f4c33 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -37,6 +37,10 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ## Unreleased
 
+### State Machine Breaking
+
+- (evm) [tharsis#840](https://github.com/tharsis/ethermint/pull/840) Store empty topics as empty array rather than nil.
+
 ## [v0.9.0] - 2021-12-01
 
 ### State Machine Breaking