fix: send battery stats even if some batteries are missing stats (#1287)

Implement battery error reporting mechanism

Added error reporting for battery information retrieval.

Handles cases like bluetooth devices where `battery` finds it but it has incomplete information about that battery, which would have otherwise caused a null pointer error.

Related: #1254

agent/battery/battery.go

@@ -5,6 +5,8 @@ package battery
 
 import (
 	"errors"
+	"fmt"
+	"os"
 	"log/slog"
 
 	"github.com/distatus/battery"
@@ -19,33 +21,60 @@ func HasReadableBattery() bool {
 		return systemHasBattery
 	}
 	haveCheckedBattery = true
-	bat, err := battery.Get(0)
+	batteries,err := battery.GetAll()
-	systemHasBattery = err == nil && bat != nil && bat.Design != 0 && bat.Full != 0
+	if err != nil {
+		// even if there's errors getting some batteries, the system
+		// definitely has a battery if the list is not empty.
+		// This list will include everything `battery` can find,
+		// including things like bluetooth devices.
+		fmt.Fprintln(os.Stderr, err)
+	}
+	systemHasBattery = len(batteries) > 0
 	if !systemHasBattery {
 		slog.Debug("No battery found", "err", err)
 	}
 	return systemHasBattery
 }
 
-// GetBatteryStats returns the current battery percent and charge state
+// GetBatteryStats returns the current battery percent and charge state 
+// percent = (current charge of all batteries) / (sum of designed/full capacity of all batteries)
 func GetBatteryStats() (batteryPercent uint8, batteryState uint8, err error) {
-	if !systemHasBattery {
+	if !HasReadableBattery() {
 		return batteryPercent, batteryState, errors.ErrUnsupported
 	}
 	batteries, err := battery.GetAll()
-	if err != nil || len(batteries) == 0 {
+	// we'll handle errors later by skipping batteries with errors, rather
-		return batteryPercent, batteryState, err
+	// than skipping everything because of the presence of some errors.
+	if len(batteries) == 0 {
+		return batteryPercent, batteryState, errors.New("no batteries")
 	}
+
 	totalCapacity := float64(0)
 	totalCharge := float64(0)
-	for _, bat := range batteries {
+	errs, partialErrs := err.(battery.Errors)
-		if bat.Design != 0 {
+
-			totalCapacity += bat.Design
+	for i, bat := range batteries {
-		} else {
+		if partialErrs && errs[i] != nil {
-			totalCapacity += bat.Full
+			// if there were some errors, like missing data, skip it
+			continue
 		}
+		if bat.Full == 0  {
+			// skip batteries with no capacity. Charge is unlikely to ever be zero, but
+			// we can't guarantee that, so don't skip based on charge.
+			continue
+		}
+		totalCapacity += bat.Full
 		totalCharge += bat.Current
 	}
+
+	if totalCapacity == 0 {
+		// for macs there's sometimes a ghost battery with 0 capacity
+		// https://github.com/distatus/battery/issues/34
+		// Instead of skipping over those batteries, we'll check for total 0 capacity
+		// and return an error. This also prevents a divide by zero.
+		return batteryPercent, batteryState, errors.New("no battery capacity")
+	}
+
 	batteryPercent = uint8(totalCharge / totalCapacity * 100)
 	batteryState = uint8(batteries[0].State.Raw)
 	return batteryPercent, batteryState, nil

agent/system.go

@@ -78,8 +78,9 @@ func (a *Agent) getSystemStats(cacheTimeMs uint16) system.Stats {
 	var systemStats system.Stats
 
 	// battery
-	if battery.HasReadableBattery() {
+	if batteryPercent, batteryState, err := battery.GetBatteryStats(); err == nil {
-		systemStats.Battery[0], systemStats.Battery[1], _ = battery.GetBatteryStats()
+		systemStats.Battery[0] = batteryPercent
+		systemStats.Battery[1] = batteryState
 	}
 
 	// cpu percent

go.sum

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