Make CRS metrics type dynamic

All CRS metrics are hardcoded to "gauge" type, this patch addresses
that.

pkg/customresourcestate/custom_resource_metrics_test.go

@@ -0,0 +1,60 @@
+package customresourcestate
+
+import (
+	"testing"
+)
+
+func TestNewCustomResourceMetrics(t *testing.T) {
+	tests := []struct {
+		r       Resource
+		wantErr bool
+		name    string
+	}{
+		{
+			// https://github.com/kubernetes/kube-state-metrics/issues/1886
+			name: "dynamic metric type (not just hardcoded to gauge)",
+			r: Resource{
+				GroupVersionKind: GroupVersionKind{
+					Group:   "apps",
+					Version: "v1",
+					Kind:    "Deployment",
+				},
+				Labels: Labels{
+					LabelsFromPath: map[string][]string{
+						"name": {"metadata", "name"},
+					},
+				},
+				Metrics: []Generator{
+					{
+						Name: "test_metrics",
+						Help: "metrics for testing",
+						Each: Metric{
+							Type: MetricTypeInfo,
+							Info: &MetricInfo{
+								MetricMeta: MetricMeta{
+									Path: []string{
+										"metadata",
+										"annotations",
+									},
+								},
+								LabelFromKey: "test",
+							},
+						},
+					},
+				},
+			},
+			wantErr: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			v, err := NewCustomResourceMetrics(tt.r)
+			expectedError := v.(*customResourceMetrics).Families[0].Each.Type() != "info"
+			if (err != nil) != tt.wantErr || expectedError {
+				t.Errorf("NewCustomResourceMetrics() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+		})
+	}
+}

pkg/customresourcestate/registry_factory.go

@@ -118,6 +118,7 @@ type compiledEach compiledMetric
 type compiledCommon struct {
 	labelFromPath map[string]valuePath
 	path          valuePath
+	t             metric.Type
 }
 
 func (c compiledCommon) Path() valuePath {
@@ -126,6 +127,9 @@ func (c compiledCommon) Path() valuePath {
 func (c compiledCommon) LabelFromPath() map[string]valuePath {
 	return c.labelFromPath
 }
+func (c compiledCommon) Type() metric.Type {
+	return c.t
+}
 
 type eachValue struct {
 	Labels map[string]string
@@ -136,6 +140,7 @@ type compiledMetric interface {
 	Values(v interface{}) (result []eachValue, err []error)
 	Path() valuePath
 	LabelFromPath() map[string]valuePath
+	Type() metric.Type
 }
 
 // newCompiledMetric returns a compiledMetric depending given the metric type.
@@ -146,6 +151,7 @@ func newCompiledMetric(m Metric) (compiledMetric, error) {
 			return nil, errors.New("expected each.gauge to not be nil")
 		}
 		cc, err := compileCommon(m.Gauge.MetricMeta)
+		cc.t = metric.Gauge
 		if err != nil {
 			return nil, fmt.Errorf("each.gauge: %w", err)
 		}
@@ -164,6 +170,7 @@ func newCompiledMetric(m Metric) (compiledMetric, error) {
 			return nil, errors.New("expected each.info to not be nil")
 		}
 		cc, err := compileCommon(m.Info.MetricMeta)
+		cc.t = metric.Info
 		if err != nil {
 			return nil, fmt.Errorf("each.info: %w", err)
 		}
@@ -176,6 +183,7 @@ func newCompiledMetric(m Metric) (compiledMetric, error) {
 			return nil, errors.New("expected each.stateSet to not be nil")
 		}
 		cc, err := compileCommon(m.StateSet.MetricMeta)
+		cc.t = metric.StateSet
 		if err != nil {
 			return nil, fmt.Errorf("each.stateSet: %w", err)
 		}
@@ -569,8 +577,7 @@ func famGen(f compiledFamily) generator.FamilyGenerator {
 	errLog := klog.V(f.ErrorLogV)
 	return generator.FamilyGenerator{
 		Name: f.Name,
-		// TODO(@rexagod): This should be dynamic.
-		Type: metric.Gauge,
+		Type: f.Each.Type(),
 		Help: f.Help,
 		GenerateFunc: func(obj interface{}) *metric.Family {
 			return generate(obj.(*unstructured.Unstructured), f, errLog)

pkg/metric/metric.go

@@ -38,12 +38,19 @@ var (
 )
 
 // Type represents the type of a metric e.g. a counter. See
-// https://prometheus.io/docs/concepts/metric_types/.
+// https://prometheus.io/docs/concepts/metric_types/ and,
+// https://github.com/OpenObservability/OpenMetrics/blob/main/specification/OpenMetrics.md#metric-types.
 type Type string
 
 // Gauge defines a Prometheus gauge.
 var Gauge Type = "gauge"
 
+// Info defines an OpenMetrics info.
+var Info Type = "info"
+
+// StateSet defines an OpenMetrics stateset.
+var StateSet Type = "stateset"
+
 // Counter defines a Prometheus counter.
 var Counter Type = "counter"