Preserve sensor chip on sysfs fallback name collision

An existing cpu_thermal chip with an unusable CPU value can still carry valid fan readings. Use a free synthetic CPU-chip key instead of replacing that entry when supplementing Pulse #2311, and cover the collision with a regression test.

Change-source: pulse-maintainer

internal/sensors/collector.go

@@ -90,6 +90,17 @@ func addMissingSysfsCPU(ctx context.Context, sensorsJSON string) string {
 		return sensorsJSON
 	}
 	for name, value := range fallback {
+		if _, exists := chips[name]; exists {
+			// A real lm-sensors chip can have the same name as the synthetic
+			// fallback. Keep its other readings rather than replacing the chip.
+			for suffix := 1; ; suffix++ {
+				alternate := fmt.Sprintf("%s-sysfs-%d", name, suffix)
+				if _, exists := chips[alternate]; !exists {
+					name = alternate
+					break
+				}
+			}
+		}
 		chips[name] = value
 	}
 	merged, err := json.Marshal(chips)

internal/sensors/collector_additional_test.go

@@ -2,6 +2,7 @@ package sensors
 
 import (
 	"context"
+	"encoding/json"
 	"os"
 	"path/filepath"
 	"strings"
@@ -122,6 +123,34 @@ func TestCollectLocal_CPUChipWithoutTemperatureGainsSysfsCPU(t *testing.T) {
 	}
 }
 
+func TestCollectLocal_SysfsCPUDoesNotReplaceMatchingSensorChip(t *testing.T) {
+	dir := t.TempDir()
+	const original = `{"cpu_thermal-virtual-0":{"temp1":{"temp1_input":"bad"},"fan1":{"fan1_input":1200}}}`
+	writeScript(t, dir, "sensors", "#!/bin/sh\necho '"+original+"'\n")
+	t.Setenv("PATH", dir+":"+os.Getenv("PATH"))
+	thermal, _ := useTestSysfsRoots(t)
+	writeSysfsSensor(t, thermal, "thermal_zone0", "type", "armada_thermal", "57000")
+
+	out, err := CollectLocal(context.Background())
+	if err != nil {
+		t.Fatal(err)
+	}
+	parsed, err := Parse(out)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if parsed.CPUPackage != 57 || parsed.Fans["cpu_thermal_fan1"] != 1200 {
+		t.Fatalf("sysfs CPU replaced existing chip readings: %+v", parsed)
+	}
+	var chips map[string]json.RawMessage
+	if err := json.Unmarshal([]byte(out), &chips); err != nil {
+		t.Fatal(err)
+	}
+	if _, ok := chips["cpu_thermal-virtual-0-sysfs-1"]; !ok {
+		t.Fatalf("expected a distinct sysfs CPU chip, got %s", out)
+	}
+}
+
 func TestCollectLocal_ExistingCPUPrecedesSysfs(t *testing.T) {
 	dir := t.TempDir()
 	const original = `{"coretemp-isa-0000":{"Package id 0":{"temp1_input":42}}}`