container: fix deserialize HNS response in GetHNSEndpointStats (#2379) (#2380)

Co-authored-by: Stefan L. <116070569+slab-msft@users.noreply.github.com>

internal/headers/hcn/hcn.go

@@ -75,13 +75,21 @@ func GetHNSEndpointStats(endpointID string) (EndpointStats, error) {
 		return EndpointStats{}, err
 	}
 
-	var stats EndpointStats
+	var response struct {
+		Success bool          `json:"Success"`
+		Error   string        `json:"Error"`
+		Output  EndpointStats `json:"Output"`
+	}
 
-	if err := json.Unmarshal([]byte(result), &stats); err != nil {
+	if err := json.Unmarshal([]byte(result), &response); err != nil {
 		return EndpointStats{}, fmt.Errorf("failed to unmarshal JSON %s: %w", result, err)
 	}
 
-	return stats, nil
+	if !response.Success {
+		return EndpointStats{}, fmt.Errorf("HNSCall failed: %s", response.Error)
+	}
+
+	return response.Output, nil
 }
 
 func hnsCall(method, path, body *uint16) (string, error) {

internal/pdh/registry/collector.go

@@ -53,7 +53,7 @@ func NewCollector[T any](object string, _ []string) (*Collector, error) {
 		counters:       make(map[string]Counter),
 	}
 
-	valueType := reflect.TypeFor[T]().Elem()
+	valueType := reflect.TypeFor[T]()
 
 	if f, ok := valueType.FieldByName("Name"); ok {
 		if f.Type.Kind() == reflect.String {

internal/pdh/registry/perflib_test.go

@@ -21,6 +21,22 @@ import (
 	"testing"
 )
 
+// TestNewCollectorStructTypeParam guards against a regression where
+// reflect.TypeFor[T]().Elem() panicked when T is a plain struct (not a pointer).
+// See https://github.com/prometheus-community/windows_exporter/issues/2365
+func TestNewCollectorStructTypeParam(t *testing.T) {
+	type systemCounterValues struct {
+		Name string
+
+		ProcessorQueueLength float64 `perfdata:"Processor Queue Length"`
+	}
+
+	_, err := NewCollector[systemCounterValues]("System", nil)
+	if err != nil {
+		t.Skipf("skipping: failed to create collector: %v", err)
+	}
+}
+
 func BenchmarkQueryPerformanceData(b *testing.B) {
 	for b.Loop() {
 		_, _ = QueryPerformanceData("Global", "")