return &cachedMetrics{wrapped: provider}
}

// GetMetrics runs the wrapped metrics provider's GetMetrics method once and
// caches the result. Will not cache result if there is an error.
// See MetricsProvider.GetMetrics
func (md *cachedMetrics) GetMetrics() (*Metrics, error) {
	md.once.cache(func() error {
		md.resultMetrics, md.resultError = md.wrapped.GetMetrics()
		return md.resultError
	})

func TestGetMetricsStatFS(t *testing.T) {
	metrics := NewMetricsStatFS("")
	actual, err := metrics.GetMetrics()
	expected := &Metrics{}
	if !volumetest.MetricsEqualIgnoreTimestamp(actual, expected) {
		t.Errorf("Expected empty Metrics from uninitialized MetricsStatFS, actual %v", *actual)
	}
	if err == nil {
		t.Errorf("Expected error when calling GetMetrics on uninitialized MetricsStatFS, actual nil")
	}

type MetricsNil struct{}

// SupportsMetrics returns false for the MetricsNil type.
func (*MetricsNil) SupportsMetrics() bool {
	return false
}

// GetMetrics returns an empty Metrics and an error.
// See MetricsProvider.GetMetrics
func (*MetricsNil) GetMetrics() (*Metrics, error) {
	return &Metrics{}, NewNotSupportedError()

example.com/depends/on/generics v1.0.0
written by hand

-- .mod --
module example.com/depends/on/generics

go 1.18

require example.com/generics v1.0.0
-- .info --
{"Version":"v1.0.0"}
-- go.mod --
module example.com/depends/on/generics

go 1.18

require example.com/generics v1.0.0
-- main.go --
package main

import "example.com/generics"

func NewMetricsStatFS(path string) MetricsProvider {
	return &metricsStatFS{path}
}

// See MetricsProvider.GetMetrics
// GetMetrics calculates the volume usage and device free space by executing "du"
// and gathering filesystem info for the Volume path.
func (md *metricsStatFS) GetMetrics() (*Metrics, error) {
	startTime := time.Now()
	defer servermetrics.CollectVolumeStatCalDuration("statfs", startTime)

	test(t, "namespaced", audit.LevelNone, stages, stages, "getLogs")
	test(t, "namespaced", audit.LevelNone, stages, stages, "getMetrics")
	test(t, "namespaced", audit.LevelMetadata, stages, stages, "getMetrics", "serviceAccounts", "default")
	test(t, "namespaced", audit.LevelRequestResponse, stages, stages, "getMetrics", "getPods", "default")
	test(t, "namespaced", audit.LevelRequestResponse, stages, stages, "getPodLogs", "getPods")

}

// See MetricsProvider.GetMetrics
// GetMetrics detects the size of the BlockMode volume for the device node
// where the Volume is attached.
//
// Note that only the capacity of the device can be detected with standard
// tools. Storage systems may have more information that they can provide by
// going through specialized APIs.
func (mb *metricsBlock) GetMetrics() (*Metrics, error) {
	startTime := time.Now()

func NewMetricsDu(path string) MetricsProvider {
	return &metricsDu{path}
}

// GetMetrics calculates the volume usage and device free space by executing "du"
// and gathering filesystem info for the Volume path.
// See MetricsProvider.GetMetrics
func (md *metricsDu) GetMetrics() (*Metrics, error) {
	metrics := &Metrics{Time: metav1.Now()}
	if md.path == "" {
		return metrics, NewNoPathDefinedError()
	}

	metrics := NewMetricsBlock("")
	actual, err := metrics.GetMetrics()
	expected := &Metrics{}
	if !volumetest.MetricsEqualIgnoreTimestamp(actual, expected) {
		t.Errorf("Expected empty Metrics from uninitialized MetricsBlock, actual %v", *actual)
	}
	if err == nil {
		t.Errorf("Expected error when calling GetMetrics on uninitialized MetricsBlock, actual nil")
	}

example.com/generics v1.0.0
written by hand

-- .mod --
module example.com/generics

go 1.18
-- .info --
{"Version":"v1.0.0"}
-- go.mod --
module example.com/generics

go 1.18
-- generics.go --
package generics

type Int interface {
	~int
}