opencensus.NewMetricProducer returns a struct instead of the metric.P…

…roducer (#4583)

CHANGELOG.md

@@ -16,6 +16,10 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 - Deprecate `go.opentelemetry.io/otel/bridge/opencensus.NewTracer` in favor of `opencensus.InstallTraceBridge`. (#4567)
 
+### Changed
+
+- `go.opentelemetry.io/otel/bridge/opencensus.NewMetricProducer` returns a `*MetricProducer` struct instead of the metric.Producer interface. (#4583)
+
 ## [1.19.0/0.42.0/0.0.7] 2023-09-28
 
 This release contains the first stable release of the OpenTelemetry Go [metric SDK].

bridge/opencensus/metric.go

@@ -26,19 +26,25 @@ import (
 	"go.opentelemetry.io/otel/sdk/metric/metricdata"
 )
 
-type producer struct {
+// MetricProducer implements the [go.opentelemetry.io/otel/sdk/metric.Producer] to provide metrics
+// from OpenCensus to the OpenTelemetry SDK.
+type MetricProducer struct {
 	manager *metricproducer.Manager
 }
 
 // NewMetricProducer returns a metric.Producer that fetches metrics from
 // OpenCensus.
-func NewMetricProducer(opts ...MetricOption) metric.Producer {
-	return &producer{
+func NewMetricProducer(opts ...MetricOption) *MetricProducer {
+	return &MetricProducer{
 		manager: metricproducer.GlobalManager(),
 	}
 }
 
-func (p *producer) Produce(context.Context) ([]metricdata.ScopeMetrics, error) {
+var _ metric.Producer = (*MetricProducer)(nil)
+
+// Produce fetches metrics from the OpenCensus manager,
+// translates them to OpenTelemetry's data model, and returns them.
+func (p *MetricProducer) Produce(context.Context) ([]metricdata.ScopeMetrics, error) {
 	producers := p.manager.GetAll()
 	data := []*ocmetricdata.Metric{}
 	for _, ocProducer := range producers {