chore: exporters/prometheus/internal/x - Generate x package from x component template

exporters/prometheus/internal/gen.go

@@ -7,3 +7,6 @@ package internal // import "go.opentelemetry.io/otel/exporters/prometheus/intern
 
 //go:generate gotmpl --body=../../../internal/shared/counter/counter.go.tmpl "--data={ \"pkg\": \"go.opentelemetry.io/otel/exporters/prometheus/internal/counter\" }" --out=counter/counter.go
 //go:generate gotmpl --body=../../../internal/shared/counter/counter_test.go.tmpl "--data={}" --out=counter/counter_test.go
+
+//go:generate gotmpl --body=../../../internal/shared/x/x.go.tmpl "--data={ \"pkg\": \"go.opentelemetry.io/otel/exporters/prometheus\" }" --out=x/x.go
+//go:generate gotmpl --body=../../../internal/shared/x/x_test.go.tmpl "--data={}" --out=x/x_test.go

exporters/prometheus/internal/x/features.go

@@ -0,0 +1,22 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package x // import "go.opentelemetry.io/otel/exporters/prometheus/internal/x"
+
+import "strings"
+
+// Observability is an experimental feature flag that determines if exporter
+// observability metrics are enabled.
+//
+// To enable this feature set the OTEL_GO_X_OBSERVABILITY environment variable
+// to the case-insensitive string value of "true" (i.e. "True" and "TRUE"
+// will also enable this).
+var Observability = newFeature(
+	[]string{"OBSERVABILITY"},
+	func(v string) (string, bool) {
+		if strings.EqualFold(v, "true") {
+			return v, true
+		}
+		return "", false
+	},
+)

exporters/prometheus/internal/x/features_test.go

@@ -0,0 +1,21 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package x
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestObservability(t *testing.T) {
+	const key = "OTEL_GO_X_OBSERVABILITY"
+	require.Contains(t, Observability.Keys(), key)
+
+	t.Run("100", run(setenv(key, "100"), assertDisabled(Observability)))
+	t.Run("true", run(setenv(key, "true"), assertEnabled(Observability, "true")))
+	t.Run("True", run(setenv(key, "True"), assertEnabled(Observability, "True")))
+	t.Run("false", run(setenv(key, "false"), assertDisabled(Observability)))
+	t.Run("empty", run(assertDisabled(Observability)))
+}