Do not expose NopHost struct (#2585)

Signed-off-by: Bogdan Drutu <bogdandrutu@gmail.com>

Author: bogdandrutu

component/componenttest/nop_host.go

@@ -19,34 +19,26 @@ import (
 	"go.opentelemetry.io/collector/config/configmodels"
 )
 
-// NopHost mocks a receiver.ReceiverHost for test purposes.
-type NopHost struct {
-}
+// nopHost mocks a receiver.ReceiverHost for test purposes.
+type nopHost struct{}
 
-var _ component.Host = (*NopHost)(nil)
+var nopHostInstance component.Host = &nopHost{}
 
-// NewNopHost returns a new instance of NopHost with proper defaults for most
-// tests.
+// NewNopHost returns a new instance of nopHost with proper defaults for most tests.
 func NewNopHost() component.Host {
-	return &NopHost{}
+	return nopHostInstance
 }
 
-// ReportFatalError is used to report to the host that the receiver encountered
-// a fatal error (i.e.: an error that the instance can't recover from) after
-// its start function has already returned.
-func (nh *NopHost) ReportFatalError(_ error) {
-	// Do nothing for now.
-}
+func (nh *nopHost) ReportFatalError(_ error) {}
 
-// GetFactory of the specified kind. Returns the factory for a component type.
-func (nh *NopHost) GetFactory(_ component.Kind, _ configmodels.Type) component.Factory {
+func (nh *nopHost) GetFactory(_ component.Kind, _ configmodels.Type) component.Factory {
 	return nil
 }
 
-func (nh *NopHost) GetExtensions() map[configmodels.Extension]component.ServiceExtension {
+func (nh *nopHost) GetExtensions() map[configmodels.Extension]component.ServiceExtension {
 	return nil
 }
 
-func (nh *NopHost) GetExporters() map[configmodels.DataType]map[configmodels.Exporter]component.Exporter {
+func (nh *nopHost) GetExporters() map[configmodels.DataType]map[configmodels.Exporter]component.Exporter {
 	return nil
 }

component/componenttest/nop_host_test.go

@@ -27,7 +27,7 @@ import (
 func TestNewNopHost(t *testing.T) {
 	nh := NewNopHost()
 	require.NotNil(t, nh)
-	require.IsType(t, &NopHost{}, nh)
+	require.IsType(t, &nopHost{}, nh)
 
 	nh.ReportFatalError(errors.New("TestError"))
 	assert.Nil(t, nh.GetExporters())

exporter/prometheusexporter/prometheus_test.go

@@ -80,7 +80,7 @@ func TestPrometheusExporter(t *testing.T) {
 			}
 
 			assert.NotNil(t, exp)
-			err = exp.Start(context.Background(), &componenttest.NopHost{})
+			err = exp.Start(context.Background(), componenttest.NewNopHost())
 
 			if tt.wantStartErr != "" {
 				require.Error(t, err)
@@ -118,7 +118,7 @@ func TestPrometheusExporter_endToEnd(t *testing.T) {
 
 	assert.NotNil(t, exp)
 
-	require.NoError(t, exp.Start(context.Background(), &componenttest.NopHost{}))
+	require.NoError(t, exp.Start(context.Background(), componenttest.NewNopHost()))
 
 	// Should accumulate multiple metrics
 	md := internaldata.OCToMetrics(internaldata.MetricsData{Metrics: metricBuilder(128, "metric_1_")})
@@ -193,7 +193,7 @@ func TestPrometheusExporter_endToEndWithTimestamps(t *testing.T) {
 	})
 
 	assert.NotNil(t, exp)
-	require.NoError(t, exp.Start(context.Background(), &componenttest.NopHost{}))
+	require.NoError(t, exp.Start(context.Background(), componenttest.NewNopHost()))
 
 	// Should accumulate multiple metrics