Ignore deprecation warnings about NameValidationScheme

CHANGELOG.md

@@ -8,6 +8,14 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ## [Unreleased]
 
+> [!WARNING]
+> This is the last version to support `model.LegacyValidation` for
+> `go.opentelemetry.io/otel/exporters/prometheus`.
+> The next version (v0.59.0) will only support the default `model.UTF8Validation`.
+>
+> See also [Change default validation scheme to UTF8Validation](https://github.com/prometheus/common/pull/724)
+> in the prometheus repository.
+
 ### Added
 
 - The `go.opentelemetry.io/otel/semconv/v1.31.0` package.
@@ -29,6 +37,10 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - `go.opentelemetry.io/otel/log/logtest` is now a separate Go module. (#6465)
 - `go.opentelemetry.io/otel/sdk/log/logtest` is now a separate Go module. (#6466)
 
+### Deprecated
+
+- Deprecate support for `model.LegacyValidation` for `go.opentelemetry.io/otel/exporters/prometheus`. (#6449)
+
 ### Fixes
 
 - Stop percent encoding header environment variables in `go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc` and `go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploghttp`. (#6392)

exporters/prometheus/config.go

@@ -5,11 +5,13 @@ package prometheus // import "go.opentelemetry.io/otel/exporters/prometheus"
 
 import (
 	"strings"
+	"sync"
 
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/common/model"
 
 	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/internal/global"
 	"go.opentelemetry.io/otel/sdk/metric"
 )
 
@@ -25,6 +27,10 @@ type config struct {
 	resourceAttributesFilter attribute.Filter
 }
 
+var logDeprecatedLegacyScheme = sync.OnceFunc(func() {
+	global.Warn("prometheus exporter legacy scheme deprecated: support for the legacy NameValidationScheme will be removed in the next release")
+})
+
 // newConfig creates a validated config configured with options.
 func newConfig(opts ...Option) config {
 	cfg := config{}
@@ -132,7 +138,8 @@ func WithoutScopeInfo() Option {
 // have special behavior based on their name.
 func WithNamespace(ns string) Option {
 	return optionFunc(func(cfg config) config {
-		if model.NameValidationScheme != model.UTF8Validation {
+		if model.NameValidationScheme != model.UTF8Validation { // nolint:staticcheck // We need this check to keep supporting the legacy scheme.
+			logDeprecatedLegacyScheme()
 			// Only sanitize if prometheus does not support UTF-8.
 			ns = model.EscapeName(ns, model.NameEscapingScheme)
 		}

exporters/prometheus/exporter.go

@@ -327,7 +327,7 @@ func getAttrs(attrs attribute.Set) ([]string, []string) {
 	values := make([]string, 0, attrs.Len())
 	itr := attrs.Iter()
 
-	if model.NameValidationScheme == model.UTF8Validation {
+	if model.NameValidationScheme == model.UTF8Validation { // nolint:staticcheck // We need this check to keep supporting the legacy scheme.
 		// Do not perform sanitization if prometheus supports UTF-8.
 		for itr.Next() {
 			kv := itr.Attribute()
@@ -413,8 +413,9 @@ var unitSuffixes = map[string]string{
 // getName returns the sanitized name, prefixed with the namespace and suffixed with unit.
 func (c *collector) getName(m metricdata.Metrics, typ *dto.MetricType) string {
 	name := m.Name
-	if model.NameValidationScheme != model.UTF8Validation {
+	if model.NameValidationScheme != model.UTF8Validation { // nolint:staticcheck // We need this check to keep supporting the legacy scheme.
 		// Only sanitize if prometheus does not support UTF-8.
+		logDeprecatedLegacyScheme()
 		name = model.EscapeName(name, model.NameEscapingScheme)
 	}
 	addCounterSuffix := !c.withoutCounterSuffixes && *typ == dto.MetricType_COUNTER

exporters/prometheus/exporter_test.go

@@ -472,10 +472,10 @@ func TestPrometheusExporter(t *testing.T) {
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {
 			if tc.disableUTF8 {
-				model.NameValidationScheme = model.LegacyValidation
+				model.NameValidationScheme = model.LegacyValidation // nolint:staticcheck // We need this check to keep supporting the legacy scheme.
 				defer func() {
 					// Reset to defaults
-					model.NameValidationScheme = model.UTF8Validation
+					model.NameValidationScheme = model.UTF8Validation // nolint:staticcheck // We need this check to keep supporting the legacy scheme.
 				}()
 			}
 			ctx := context.Background()
@@ -1029,13 +1029,13 @@ func TestExemplars(t *testing.T) {
 	} {
 		t.Run(tc.name, func(t *testing.T) {
 			originalEscapingScheme := model.NameEscapingScheme
-			originalValidationScheme := model.NameValidationScheme
+			originalValidationScheme := model.NameValidationScheme // nolint:staticcheck // We need this check to keep supporting the legacy scheme.
 			model.NameEscapingScheme = tc.escapingScheme
-			model.NameValidationScheme = tc.validationScheme
+			model.NameValidationScheme = tc.validationScheme // nolint:staticcheck // We need this check to keep supporting the legacy scheme.
 			// Restore original value after the test is complete
 			defer func() {
 				model.NameEscapingScheme = originalEscapingScheme
-				model.NameValidationScheme = originalValidationScheme
+				model.NameValidationScheme = originalValidationScheme // nolint:staticcheck // We need this check to keep supporting the legacy scheme.
 			}()
 			// initialize registry exporter
 			ctx := context.Background()