op-service: jsonutil sorted-map

op-service/jsonutil/sortedmap.go

+package jsonutil
+
+import (
+	"encoding/json"
+	"fmt"
+	"sort"
+)
+
+// LazySortedJsonMap provides sorted encoding order for JSON maps.
+// The sorting is lazy: in-memory it's just a map, until it sorts just-in-time when the map is encoded to JSON.
+// Warning: the just-in-time sorting requires a full allocation of the map structure and keys slice during encoding.
+// Sorting order is not enforced when decoding from JSON.
+type LazySortedJsonMap[K comparable, V any] map[K]V
+
+func (m LazySortedJsonMap[K, V]) MarshalJSON() ([]byte, error) {
+	keys := make([]string, 0, len(m))
+	values := make(map[string]V)
+	for k, v := range m {
+		s := fmt.Sprintf("%q", any(k)) // format as quoted string
+		keys = append(keys, s)
+		values[s] = v
+	}
+	sort.Strings(keys)
+	var out []byte
+	out = append(out, '{')
+	for i, k := range keys {
+		out = append(out, k...) // quotes are already included
+		out = append(out, ':')
+		v, err := json.Marshal(values[k])
+		if err != nil {
+			return nil, fmt.Errorf("failed to encode value of %s: %w", k, err)
+		}
+		out = append(out, v...)
+		if i != len(keys)-1 {
+			out = append(out, ',')
+		}
+	}
+	out = append(out, '}')
+	return out, nil
+}
+
+func (m *LazySortedJsonMap[K, V]) UnmarshalJSON(data []byte) error {
+	return json.Unmarshal(data, (*map[K]V)(m))
+}

op-service/jsonutil/sortedmap_test.go

+package jsonutil
+
+import (
+	"encoding/json"
+	"fmt"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/stretchr/testify/require"
+)
+
+type LazySortedJsonMapTestCase[K comparable, V any] struct {
+	Object LazySortedJsonMap[K, V]
+	Json   string
+}
+
+func (tc *LazySortedJsonMapTestCase[K, V]) Run(t *testing.T) {
+	t.Run("Marshal", func(t *testing.T) {
+		got, err := json.Marshal(tc.Object)
+		require.NoError(t, err)
+		require.Equal(t, tc.Json, string(got), "json output must match")
+	})
+	t.Run("Unmarshal", func(t *testing.T) {
+		var dest LazySortedJsonMap[K, V]
+		err := json.Unmarshal([]byte(tc.Json), &dest)
+		require.NoError(t, err)
+		require.Equal(t, len(tc.Object), len(dest), "lengths match")
+		for k, v := range tc.Object {
+			require.Equal(t, v, dest[k], "values of %q match", k)
+		}
+	})
+}
+
+func TestLazySortedJsonMap(t *testing.T) {
+	testCases := []interface{ Run(t *testing.T) }{
+		&LazySortedJsonMapTestCase[string, int]{Object: LazySortedJsonMap[string, int]{}, Json: `{}`},
+		&LazySortedJsonMapTestCase[string, int]{Object: LazySortedJsonMap[string, int]{"a": 1, "c": 2, "b": 3}, Json: `{"a":1,"b":3,"c":2}`},
+		&LazySortedJsonMapTestCase[common.Address, int]{Object: LazySortedJsonMap[common.Address, int]{
+			common.HexToAddress("0x4100000000000000000000000000000000000000"): 123,
+			common.HexToAddress("0x4200000000000000000000000000000000000000"): 100,
+			common.HexToAddress("0x4200000000000000000000000000000000000001"): 100,
+		},
+			Json: `{"0x4100000000000000000000000000000000000000":123,` +
+				`"0x4200000000000000000000000000000000000000":100,` +
+				`"0x4200000000000000000000000000000000000001":100}`},
+	}
+	for i, tc := range testCases {
+		t.Run(fmt.Sprintf("case %d", i), tc.Run)
+	}
+}