Handle singular labels in allowlist

Handle singular labels in allowlist failing when such a label is
supplied, in order to keep the behaviour in sync with --resources.

Signed-off-by: Pranshu Srivastava <rexagod@gmail.com>

internal/store/builder.go

@@ -200,10 +200,16 @@ func (b *Builder) WithAllowAnnotations(annotations map[string][]string) {
 }
 
 // WithAllowLabels configures which labels can be returned for metrics
-func (b *Builder) WithAllowLabels(labels map[string][]string) {
+func (b *Builder) WithAllowLabels(labels map[string][]string) error {
 	if len(labels) > 0 {
+		for label := range labels {
+			if !resourceExists(label) {
+				return fmt.Errorf("resource %s does not exist. Available resources: %s", label, strings.Join(availableResources(), ","))
+			}
+		}
 		b.allowLabelsList = labels
 	}
+	return nil
 }
 
 // Build initializes and registers all enabled stores.

pkg/app/server.go

@@ -149,7 +149,9 @@ func RunKubeStateMetrics(ctx context.Context, opts *options.Options, factories .
 	storeBuilder.WithCustomResourceClients(customResourceClients)
 	storeBuilder.WithSharding(opts.Shard, opts.TotalShards)
 	storeBuilder.WithAllowAnnotations(opts.AnnotationsAllowList)
-	storeBuilder.WithAllowLabels(opts.LabelsAllowList)
+	if err := storeBuilder.WithAllowLabels(opts.LabelsAllowList); err != nil {
+		return fmt.Errorf("failed to set up labels allowlist: %v", err)
+	}
 
 	ksmMetricsRegistry.MustRegister(
 		collectors.NewProcessCollector(collectors.ProcessCollectorOpts{}),

pkg/builder/types/interfaces.go

@@ -44,7 +44,7 @@ type BuilderInterface interface {
 	WithUsingAPIServerCache(u bool)
 	WithFamilyGeneratorFilter(l generator.FamilyGeneratorFilter)
 	WithAllowAnnotations(a map[string][]string)
-	WithAllowLabels(l map[string][]string)
+	WithAllowLabels(l map[string][]string) error
 	WithGenerateStoresFunc(f BuildStoresFunc)
 	WithGenerateCustomResourceStoresFunc(f BuildCustomResourceStoresFunc)
 	DefaultGenerateStoresFunc() BuildStoresFunc