metrics testing: add type aliases to avoid direct prometheus imports

In tests it is sometimes unavoidable to use the Prometheus types directly,
for example when writing a custom gatherer which needs to normalize data
before testing it. device_taint_eviction_test.go does this to strip
out unpredictable data in a histogram.

With type aliases in a package that is explicitly meant for tests we
can avoid adding exceptions for such tests to the global exception list.

Author: pohly

hack/verify-prometheus-imports.sh

@@ -37,7 +37,6 @@ source "${KUBE_ROOT}/hack/lib/util.sh"
 # See: https://github.com/kubernetes/kubernetes/issues/89267
 allowed_prometheus_importers=(
   ./cluster/images/etcd-version-monitor/etcd-version-monitor.go
-  ./pkg/controller/devicetainteviction/device_taint_eviction_test.go
   ./staging/src/k8s.io/component-base/metrics/prometheusextension/timing_histogram.go
   ./staging/src/k8s.io/component-base/metrics/prometheusextension/timing_histogram_test.go
   ./staging/src/k8s.io/component-base/metrics/prometheusextension/timing_histogram_vec.go

pkg/controller/devicetainteviction/device_taint_eviction_test.go

@@ -32,8 +32,6 @@ import (
 	"github.com/onsi/gomega"
 	"github.com/onsi/gomega/gstruct"
 	gomegatypes "github.com/onsi/gomega/types"
-	"github.com/prometheus/client_golang/prometheus"
-	dto "github.com/prometheus/client_model/go"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
@@ -1205,7 +1203,7 @@ device_taint_eviction_controller_pod_deletions_total %[1]d
 		controller.metrics.PodDeletionsTotal.FQName(),
 		controller.metrics.PodDeletionsLatency.FQName(),
 	}
-	gather := func() ([]*dto.MetricFamily, error) {
+	gather := func() ([]*metricstestutil.MetricFamily, error) {
 		got, err := controller.metrics.Gather()
 		for _, mf := range got {
 			for _, m := range mf.Metric {
@@ -1218,7 +1216,7 @@ device_taint_eviction_controller_pod_deletions_total %[1]d
 		return got, err
 	}
 
-	return metricstestutil.GatherAndCompare(prometheus.GathererFunc(gather), strings.NewReader(expectedMetric), names...)
+	return metricstestutil.GatherAndCompare(metricstestutil.GathererFunc(gather), strings.NewReader(expectedMetric), names...)
 }
 
 // TestEviction runs through the full flow of starting the controller and evicting one pod.

staging/src/k8s.io/component-base/metrics/testutil/testutil.go

@@ -20,7 +20,9 @@ import (
 	"fmt"
 	"io"
 
+	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/testutil"
+	dto "github.com/prometheus/client_model/go"
 
 	apimachineryversion "k8s.io/apimachinery/pkg/version"
 	"k8s.io/component-base/metrics"
@@ -33,6 +35,14 @@ type TB interface {
 	Fatalf(format string, args ...any)
 }
 
+// MetricFamily is a type alias which enables writing gatherers in tests
+// without importing prometheus directly (https://github.com/kubernetes/kubernetes/issues/99876).
+type MetricFamily = dto.MetricFamily
+
+// GathererFunc is a type alias which enables writing gatherers as a function in tests
+// without importing prometheus directly (https://github.com/kubernetes/kubernetes/issues/99876).
+type GathererFunc = prometheus.GathererFunc
+
 // CollectAndCompare registers the provided Collector with a newly created
 // pedantic Registry. It then does the same as GatherAndCompare, gathering the
 // metrics from the pedantic Registry.