From 833b3a0c8dbe7df87f901ce4dcd988659fad1f13 Mon Sep 17 00:00:00 2001
From: Stephen Buttolph <stephen@avalabs.org>
Date: Tue, 3 Sep 2024 11:06:32 -0400
Subject: [PATCH] Support unmarshalling of json byte slices (#3354)

---
 vms/avm/service_test.go        | 16 +++++-----
 vms/platformvm/service_test.go |  4 +++
 vms/types/blob_data.go         | 23 ++++++++++++++
 vms/types/blob_data_test.go    | 56 ++++++++++++++++++++++++++++++++++
 4 files changed, 91 insertions(+), 8 deletions(-)
 create mode 100644 vms/types/blob_data_test.go

diff --git a/vms/avm/service_test.go b/vms/avm/service_test.go
index 6f44e469a75..c6e20c6ecb5 100644
--- a/vms/avm/service_test.go
+++ b/vms/avm/service_test.go
@@ -660,7 +660,7 @@ func TestServiceGetTxJSON_ExportTx(t *testing.T) {
 				}
 			}
 		],
-		"memo": "0x",
+		"memo": null,
 		"destinationChain": "2mcwQKiD8VEspmMJpL1dc7okQQ5dDVAWeCBZ7FWBFAbxpv3t7w",
 		"exportedOutputs": [
 			{
@@ -800,7 +800,7 @@ func TestServiceGetTxJSON_CreateAssetTx(t *testing.T) {
 				}
 			}
 		],
-		"memo": "0x",
+		"memo": null,
 		"name": "Team Rocket",
 		"symbol": "TR",
 		"denomination": 0,
@@ -972,7 +972,7 @@ func TestServiceGetTxJSON_OperationTxWithNftxMintOp(t *testing.T) {
 				}
 			}
 		],
-		"memo": "0x",
+		"memo": null,
 		"operations": [
 			{
 				"assetID": %[4]q,
@@ -1117,7 +1117,7 @@ func TestServiceGetTxJSON_OperationTxWithMultipleNftxMintOp(t *testing.T) {
 				}
 			}
 		],
-		"memo": "0x",
+		"memo": null,
 		"operations": [
 			{
 				"assetID": %[4]q,
@@ -1292,7 +1292,7 @@ func TestServiceGetTxJSON_OperationTxWithSecpMintOp(t *testing.T) {
 				}
 			}
 		],
-		"memo": "0x",
+		"memo": null,
 		"operations": [
 			{
 				"assetID": %[4]q,
@@ -1439,7 +1439,7 @@ func TestServiceGetTxJSON_OperationTxWithMultipleSecpMintOp(t *testing.T) {
 				}
 			}
 		],
-		"memo": "0x",
+		"memo": null,
 		"operations": [
 			{
 				"assetID": %[4]q,
@@ -1617,7 +1617,7 @@ func TestServiceGetTxJSON_OperationTxWithPropertyFxMintOp(t *testing.T) {
 				}
 			}
 		],
-		"memo": "0x",
+		"memo": null,
 		"operations": [
 			{
 				"assetID": %[4]q,
@@ -1759,7 +1759,7 @@ func TestServiceGetTxJSON_OperationTxWithPropertyFxMintOpMultiple(t *testing.T)
 				}
 			}
 		],
-		"memo": "0x",
+		"memo": null,
 		"operations": [
 			{
 				"assetID": %[4]q,
diff --git a/vms/platformvm/service_test.go b/vms/platformvm/service_test.go
index c896066142e..7b3252c140e 100644
--- a/vms/platformvm/service_test.go
+++ b/vms/platformvm/service_test.go
@@ -234,6 +234,7 @@ func TestGetTx(t *testing.T) {
 					constants.AVMID,
 					[]ids.ID{},
 					"chain name",
+					common.WithMemo([]byte{}),
 				)
 				require.NoError(t, err)
 				return tx
@@ -266,6 +267,7 @@ func TestGetTx(t *testing.T) {
 					rewardsOwner,
 					rewardsOwner,
 					0,
+					common.WithMemo([]byte{}),
 				)
 				require.NoError(t, err)
 				return tx
@@ -289,6 +291,7 @@ func TestGetTx(t *testing.T) {
 							},
 						},
 					}},
+					common.WithMemo([]byte{}),
 				)
 				require.NoError(t, err)
 				return tx
@@ -792,6 +795,7 @@ func TestGetBlock(t *testing.T) {
 				constants.AVMID,
 				[]ids.ID{},
 				"chain name",
+				common.WithMemo([]byte{}),
 			)
 			require.NoError(err)
 
diff --git a/vms/types/blob_data.go b/vms/types/blob_data.go
index cee4fe7ba4d..155d6a29d7e 100644
--- a/vms/types/blob_data.go
+++ b/vms/types/blob_data.go
@@ -9,13 +9,36 @@ import (
 	"github.com/ava-labs/avalanchego/utils/formatting"
 )
 
+const nullStr = "null"
+
 // JSONByteSlice represents [[]byte] that is json marshalled to hex
 type JSONByteSlice []byte
 
 func (b JSONByteSlice) MarshalJSON() ([]byte, error) {
+	if b == nil {
+		return []byte(nullStr), nil
+	}
+
 	hexData, err := formatting.Encode(formatting.HexNC, b)
 	if err != nil {
 		return nil, err
 	}
 	return json.Marshal(hexData)
 }
+
+func (b *JSONByteSlice) UnmarshalJSON(jsonBytes []byte) error {
+	if string(jsonBytes) == nullStr {
+		return nil
+	}
+
+	var hexData string
+	if err := json.Unmarshal(jsonBytes, &hexData); err != nil {
+		return err
+	}
+	v, err := formatting.Decode(formatting.HexNC, hexData)
+	if err != nil {
+		return err
+	}
+	*b = v
+	return nil
+}
diff --git a/vms/types/blob_data_test.go b/vms/types/blob_data_test.go
new file mode 100644
index 00000000000..82c692a9468
--- /dev/null
+++ b/vms/types/blob_data_test.go
@@ -0,0 +1,56 @@
+// Copyright (C) 2019-2024, Ava Labs, Inc. All rights reserved.
+// See the file LICENSE for licensing terms.
+
+package types
+
+import (
+	"encoding/json"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestJSON(t *testing.T) {
+	tests := []struct {
+		name         string
+		value        JSONByteSlice
+		expectedJSON string
+	}{
+		{
+			name:         "nil",
+			value:        nil,
+			expectedJSON: nullStr,
+		},
+		{
+			name:         "empty",
+			value:        []byte{},
+			expectedJSON: `"0x"`,
+		},
+		{
+			name:         "not empty",
+			value:        []byte{0, 1, 2, 3},
+			expectedJSON: `"0x00010203"`,
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			require := require.New(t)
+
+			jsonBytes, err := json.Marshal(test.value)
+			require.NoError(err)
+			require.Equal(test.expectedJSON, string(jsonBytes))
+
+			var unmarshaled JSONByteSlice
+			require.NoError(json.Unmarshal(jsonBytes, &unmarshaled))
+			require.Equal(test.value, unmarshaled)
+		})
+	}
+}
+
+func TestUnmarshalJSONNullKeepsInitialValue(t *testing.T) {
+	require := require.New(t)
+
+	unmarshaled := JSONByteSlice{1, 2, 3}
+	require.NoError(json.Unmarshal([]byte(nullStr), &unmarshaled))
+	require.Equal(JSONByteSlice{1, 2, 3}, unmarshaled)
+}