From 395c0317de0febe0933dd8b31258ca97563acde0 Mon Sep 17 00:00:00 2001
From: Bogdan Drutu <bogdandrutu@gmail.com>
Date: Thu, 16 Dec 2021 11:35:55 -0800
Subject: [PATCH] Fixes the instrument kind for noop async instruments

Signed-off-by: Bogdan Drutu <bogdandrutu@gmail.com>
---
 internal/metric/registry/registry_test.go | 11 +++++++++++
 metric/sdkapi/noop.go                     | 24 ++++++++++++++++++-----
 2 files changed, 30 insertions(+), 5 deletions(-)

diff --git a/internal/metric/registry/registry_test.go b/internal/metric/registry/registry_test.go
index 04884898822..05cbeddf316 100644
--- a/internal/metric/registry/registry_test.go
+++ b/internal/metric/registry/registry_test.go
@@ -19,6 +19,7 @@ import (
 	"errors"
 	"testing"
 
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
 	"go.opentelemetry.io/otel/internal/metric/registry"
@@ -125,3 +126,13 @@ func TestRegistryDiffInstruments(t *testing.T) {
 		}
 	}
 }
+
+func TestDoubleNewInstrument(t *testing.T) {
+	reg := registry.NewUniqueInstrumentMeterImpl(
+		metrictest.NewMeterProvider().Meter("meter").MeterImpl(),
+	)
+	_, err := reg.NewAsyncInstrument(sdkapi.NewNoopAsyncInstrument().Descriptor(), nil)
+	require.NoError(t, err)
+	_, err = reg.NewSyncInstrument(sdkapi.NewNoopSyncInstrument().Descriptor())
+	assert.Error(t, err)
+}
diff --git a/metric/sdkapi/noop.go b/metric/sdkapi/noop.go
index 986f5efec45..f22895dae6f 100644
--- a/metric/sdkapi/noop.go
+++ b/metric/sdkapi/noop.go
@@ -21,7 +21,9 @@ import (
 	"go.opentelemetry.io/otel/metric/number"
 )
 
-type noopInstrument struct{}
+type noopInstrument struct {
+	descriptor Descriptor
+}
 type noopSyncInstrument struct{ noopInstrument }
 type noopAsyncInstrument struct{ noopInstrument }
 
@@ -31,21 +33,33 @@ var _ AsyncImpl = noopAsyncInstrument{}
 // NewNoopSyncInstrument returns a No-op implementation of the
 // synchronous instrument interface.
 func NewNoopSyncInstrument() SyncImpl {
-	return noopSyncInstrument{}
+	return noopSyncInstrument{
+		noopInstrument{
+			descriptor: Descriptor{
+				instrumentKind: CounterInstrumentKind,
+			},
+		},
+	}
 }
 
 // NewNoopAsyncInstrument returns a No-op implementation of the
 // asynchronous instrument interface.
 func NewNoopAsyncInstrument() AsyncImpl {
-	return noopAsyncInstrument{}
+	return noopAsyncInstrument{
+		noopInstrument{
+			descriptor: Descriptor{
+				instrumentKind: CounterObserverInstrumentKind,
+			},
+		},
+	}
 }
 
 func (noopInstrument) Implementation() interface{} {
 	return nil
 }
 
-func (noopInstrument) Descriptor() Descriptor {
-	return Descriptor{}
+func (n noopInstrument) Descriptor() Descriptor {
+	return n.descriptor
 }
 
 func (noopSyncInstrument) RecordOne(context.Context, number.Number, []attribute.KeyValue) {