Move metric No-Op to metric/noop (#3941)

* Revert "Revert "Move metric No-Op to metric/noop (#3893)" (#3921)"

This reverts commit 795ad97.

* Add PR number

* Move example_test back to `otel/metric`

* Update CHANGELOG.md

Co-authored-by: Robert Pająk <[email protected]>

* Remove redundant panic tests

* Update noop pkg docs

---------

Co-authored-by: Robert Pająk <[email protected]>

CHANGELOG.md

@@ -8,6 +8,11 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ## [Unreleased]
 
+### Changed
+
+- Move No-Op implementation from `go.opentelemetry.io/otel/metric` into its own package `go.opentelemetry.io/otel/metric/noop`. (#3941)
+  - `metric.NewNoopMeterProvider` is replaced with `noop.NewMeterProvider`
+
 ### Fixed
 
 - `TracerProvider` allows calling `Tracer()` while it's shutting down.

internal/global/instruments_test.go

@@ -21,6 +21,7 @@ import (
 	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/metric"
 	"go.opentelemetry.io/otel/metric/instrument"
+	"go.opentelemetry.io/otel/metric/noop"
 )
 
 func testFloat64Race(interact func(context.Context, float64, ...attribute.KeyValue), setDelegate func(metric.Meter)) {
@@ -36,7 +37,7 @@ func testFloat64Race(interact func(context.Context, float64, ...attribute.KeyVal
 		}
 	}()
 
-	setDelegate(metric.NewNoopMeterProvider().Meter(""))
+	setDelegate(noop.NewMeterProvider().Meter(""))
 	close(finish)
 }
 
@@ -53,7 +54,7 @@ func testInt64Race(interact func(context.Context, int64, ...attribute.KeyValue),
 		}
 	}()
 
-	setDelegate(metric.NewNoopMeterProvider().Meter(""))
+	setDelegate(noop.NewMeterProvider().Meter(""))
 	close(finish)
 }
 

internal/global/meter_test.go

@@ -25,6 +25,7 @@ import (
 
 	"go.opentelemetry.io/otel/metric"
 	"go.opentelemetry.io/otel/metric/instrument"
+	"go.opentelemetry.io/otel/metric/noop"
 )
 
 func TestMeterProviderRace(t *testing.T) {
@@ -41,7 +42,7 @@ func TestMeterProviderRace(t *testing.T) {
 		}
 	}()
 
-	mp.setDelegate(metric.NewNoopMeterProvider())
+	mp.setDelegate(noop.NewMeterProvider())
 	close(finish)
 }
 
@@ -84,7 +85,7 @@ func TestMeterRace(t *testing.T) {
 	}()
 
 	wg.Wait()
-	mtr.setDelegate(metric.NewNoopMeterProvider())
+	mtr.setDelegate(noop.NewMeterProvider())
 	close(finish)
 }
 
@@ -113,7 +114,7 @@ func TestUnregisterRace(t *testing.T) {
 	_ = reg.Unregister()
 
 	wg.Wait()
-	mtr.setDelegate(metric.NewNoopMeterProvider())
+	mtr.setDelegate(noop.NewMeterProvider())
 	close(finish)
 }
 

internal/global/state_test.go

@@ -20,6 +20,7 @@ import (
 	"github.com/stretchr/testify/assert"
 
 	"go.opentelemetry.io/otel/metric"
+	"go.opentelemetry.io/otel/metric/noop"
 	"go.opentelemetry.io/otel/propagation"
 	"go.opentelemetry.io/otel/trace"
 )
@@ -152,7 +153,7 @@ func TestSetMeterProvider(t *testing.T) {
 	t.Run("First Set() should replace the delegate", func(t *testing.T) {
 		ResetForTest(t)
 
-		SetMeterProvider(metric.NewNoopMeterProvider())
+		SetMeterProvider(noop.NewMeterProvider())
 
 		_, ok := MeterProvider().(*meterProvider)
 		if ok {
@@ -165,7 +166,7 @@ func TestSetMeterProvider(t *testing.T) {
 
 		mp := MeterProvider()
 
-		SetMeterProvider(metric.NewNoopMeterProvider())
+		SetMeterProvider(noop.NewMeterProvider())
 
 		dmp := mp.(*meterProvider)