fix: preserve battery array encoding with json v2

internal/entities/system/system.go

@@ -44,7 +44,7 @@ type Stats struct {
 	MaxBandwidth [2]uint64 `json:"bm,omitzero" cbor:"-"`                   // [sent bytes, recv bytes]
 	// TODO: remove other load fields in future release in favor of load avg array
 	LoadAvg           [3]float64           `json:"la,omitempty" cbor:"28,keyasint"`
-	Battery           [2]uint8             `json:"bat,omitzero" cbor:"29,keyasint,omitzero"`    // [percent, charge state]
+	Battery           Battery              `json:"bat,omitzero" cbor:"29,keyasint,omitzero"`    // [percent, charge state]
 	NetworkInterfaces map[string][4]uint64 `json:"ni,omitempty" cbor:"31,keyasint,omitempty"`   // [upload bytes, download bytes, total upload, total download]
 	DiskIO            [2]uint64            `json:"dio,omitzero" cbor:"32,keyasint,omitzero"`    // [read bytes, write bytes]
 	MaxDiskIO         [2]uint64            `json:"diom,omitzero" cbor:"-"`                      // [max read bytes, max write bytes]
@@ -71,6 +71,15 @@ func (s Uint8Slice) MarshalJSON() ([]byte, error) {
 	return json.Marshal(arr)
 }
 
+// Battery stores the representative battery's percent and charge state.
+// Its custom JSON encoding keeps the public and persisted representation as a
+// numeric tuple under both encoding/json v1 and v2.
+type Battery [2]uint8
+
+func (b Battery) MarshalJSON() ([]byte, error) {
+	return json.Marshal([2]uint16{uint16(b[0]), uint16(b[1])})
+}
+
 type GPUData struct {
 	Name        string             `json:"n" cbor:"0,keyasint"`
 	Temperature float64            `json:"-"`
@@ -155,8 +164,8 @@ type Info struct {
 	LoadAvg        [3]float64         `json:"la,omitempty" cbor:"19,keyasint"`
 	ConnectionType ConnectionType     `json:"ct,omitempty" cbor:"20,keyasint,omitempty,omitzero"`
 	ExtraFsPct     map[string]float64 `json:"efs,omitempty" cbor:"21,keyasint,omitempty"`
-	Services       []uint16           `json:"sv,omitempty" cbor:"22,keyasint,omitempty"` // [totalServices, numFailedServices]
-	Battery        [2]uint8           `json:"bat,omitzero" cbor:"23,keyasint,omitzero"`  // [percent, charge state]
+	Services       []uint16           `json:"sv,omitempty" cbor:"22,keyasint,omitempty"`  // [totalServices, numFailedServices]
+	Battery        Battery            `json:"bat,omitzero" cbor:"23,keyasint,omitzero"`   // [percent, charge state]
 	RootDiskName   string             `json:"rdn,omitempty" cbor:"24,keyasint,omitempty"` // custom name for root disk (set via FILESYSTEM=device__name)
 }
 

internal/entities/system/system_test.go

@@ -2,6 +2,7 @@ package system
 
 import (
 	"encoding/json"
+	jsonv2 "encoding/json/v2"
 	"testing"
 
 	"github.com/fxamacker/cbor/v2"
@@ -12,12 +13,19 @@ import (
 func TestStatsBatteryTransport(t *testing.T) {
 	stats := Stats{Battery: [2]uint8{0, 1}, Batteries: map[string]uint8{"Primary": 0, "Mouse": 75}}
 
-	jsonData, err := json.Marshal(stats)
-	require.NoError(t, err)
-	var jsonPayload map[string]any
-	require.NoError(t, json.Unmarshal(jsonData, &jsonPayload))
-	assert.Equal(t, []any{float64(0), float64(1)}, jsonPayload["bat"])
-	assert.Equal(t, map[string]any{"Primary": float64(0), "Mouse": float64(75)}, jsonPayload["bats"])
+	for name, marshal := range map[string]func(any) ([]byte, error){
+		"json_v1": json.Marshal,
+		"json_v2": func(value any) ([]byte, error) { return jsonv2.Marshal(value) },
+	} {
+		t.Run(name, func(t *testing.T) {
+			jsonData, err := marshal(stats)
+			require.NoError(t, err)
+			var jsonPayload map[string]any
+			require.NoError(t, json.Unmarshal(jsonData, &jsonPayload))
+			assert.Equal(t, []any{float64(0), float64(1)}, jsonPayload["bat"])
+			assert.Equal(t, map[string]any{"Primary": float64(0), "Mouse": float64(75)}, jsonPayload["bats"])
+		})
+	}
 
 	cborData, err := cbor.Marshal(stats)
 	require.NoError(t, err)
@@ -27,6 +35,12 @@ func TestStatsBatteryTransport(t *testing.T) {
 	assert.Equal(t, stats.Batteries, decoded.Batteries)
 }
 
+func TestStatsBatteryNumericArrayUnmarshal(t *testing.T) {
+	var stats Stats
+	require.NoError(t, json.Unmarshal([]byte(`{"bat":[50,4]}`), &stats))
+	assert.Equal(t, Battery{50, 4}, stats.Battery)
+}
+
 func TestStatsLegacyBatteryPayload(t *testing.T) {
 	data, err := json.Marshal(Stats{Battery: [2]uint8{50, 4}})
 	require.NoError(t, err)

internal/records/records_averaging_test.go

@@ -620,7 +620,7 @@ func TestAverageSystemStatsSlice_ZeroRepresentativeBattery(t *testing.T) {
 		{Battery: [2]uint8{0, 1}, Batteries: map[string]uint8{"Primary": 0}},
 		{},
 	})
-	assert.Equal(t, [2]uint8{0, 1}, result.Battery)
+	assert.Equal(t, system.Battery{0, 1}, result.Battery)
 	assert.Equal(t, map[string]uint8{"Primary": 0}, result.Batteries)
 }