From 55fb2bb57b47133d0b966e4d55151fba47aae057 Mon Sep 17 00:00:00 2001
From: Tyler Yahn <MrAlias@users.noreply.github.com>
Date: Wed, 12 Jul 2023 15:10:40 -0700
Subject: [PATCH] Log an error for an empty view criteria (#4307)

* Log an error for an empty view

Resolves #4149

* Add changelog entry
---
 CHANGELOG.md            |  1 +
 sdk/metric/view.go      |  5 +++++
 sdk/metric/view_test.go | 10 ++++++++++
 3 files changed, 16 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2f69a0ddfd6..8759f726a18 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -33,6 +33,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 ### Fixed
 
 - Correctly format log messages from the `go.opentelemetry.io/otel/exporters/zipkin` exporter. (#4143)
+- Log an error for calls to `NewView` in `go.opentelemetry.io/otel/sdk/metric` that have empty criteria. (#4307)
 
 ## [1.16.0/0.39.0] 2023-05-18
 
diff --git a/sdk/metric/view.go b/sdk/metric/view.go
index 9dab839f003..f1df24466bc 100644
--- a/sdk/metric/view.go
+++ b/sdk/metric/view.go
@@ -25,6 +25,7 @@ import (
 
 var (
 	errMultiInst = errors.New("name replacement for multiple instruments")
+	errEmptyView = errors.New("no criteria provided for view")
 
 	emptyView = func(Instrument) (Stream, bool) { return Stream{}, false }
 )
@@ -55,6 +56,10 @@ type View func(Instrument) (Stream, bool)
 // View, create a View directly.
 func NewView(criteria Instrument, mask Stream) View {
 	if criteria.empty() {
+		global.Error(
+			errEmptyView, "dropping view",
+			"mask", mask,
+		)
 		return emptyView
 	}
 
diff --git a/sdk/metric/view_test.go b/sdk/metric/view_test.go
index 439e7819c2d..b8f6c921468 100644
--- a/sdk/metric/view_test.go
+++ b/sdk/metric/view_test.go
@@ -467,6 +467,16 @@ func TestNewViewAggregationErrorLogged(t *testing.T) {
 	assert.Equal(t, 1, l.ErrorN())
 }
 
+func TestNewViewEmptyViewErrorLogged(t *testing.T) {
+	var got string
+	otel.SetLogger(funcr.New(func(_, args string) {
+		got = args
+	}, funcr.Options{Verbosity: 6}))
+
+	_ = NewView(Instrument{}, Stream{})
+	assert.Contains(t, got, errEmptyView.Error())
+}
+
 func TestNewViewMultiInstMatchErrorLogged(t *testing.T) {
 	var got string
 	otel.SetLogger(funcr.New(func(_, args string) {