chore: go mod tidy / vendor / make deps

vendor/go.opentelemetry.io/otel/sdk/trace/internal/x/x.go

@@ -0,0 +1,63 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+// Package x documents experimental features for [go.opentelemetry.io/otel/sdk/trace].
+package x // import "go.opentelemetry.io/otel/sdk/trace/internal/x"
+
+import (
+	"os"
+	"strings"
+)
+
+// SelfObservability is an experimental feature flag that determines if SDK
+// self-observability metrics are enabled.
+//
+// To enable this feature set the OTEL_GO_X_SELF_OBSERVABILITY environment variable
+// to the case-insensitive string value of "true" (i.e. "True" and "TRUE"
+// will also enable this).
+var SelfObservability = newFeature("SELF_OBSERVABILITY", func(v string) (string, bool) {
+	if strings.EqualFold(v, "true") {
+		return v, true
+	}
+	return "", false
+})
+
+// Feature is an experimental feature control flag. It provides a uniform way
+// to interact with these feature flags and parse their values.
+type Feature[T any] struct {
+	key   string
+	parse func(v string) (T, bool)
+}
+
+func newFeature[T any](suffix string, parse func(string) (T, bool)) Feature[T] {
+	const envKeyRoot = "OTEL_GO_X_"
+	return Feature[T]{
+		key:   envKeyRoot + suffix,
+		parse: parse,
+	}
+}
+
+// Key returns the environment variable key that needs to be set to enable the
+// feature.
+func (f Feature[T]) Key() string { return f.key }
+
+// Lookup returns the user configured value for the feature and true if the
+// user has enabled the feature. Otherwise, if the feature is not enabled, a
+// zero-value and false are returned.
+func (f Feature[T]) Lookup() (v T, ok bool) {
+	// https://github.com/open-telemetry/opentelemetry-specification/blob/62effed618589a0bec416a87e559c0a9d96289bb/specification/configuration/sdk-environment-variables.md#parsing-empty-value
+	//
+	// > The SDK MUST interpret an empty value of an environment variable the
+	// > same way as when the variable is unset.
+	vRaw := os.Getenv(f.key)
+	if vRaw == "" {
+		return v, ok
+	}
+	return f.parse(vRaw)
+}
+
+// Enabled reports whether the feature is enabled.
+func (f Feature[T]) Enabled() bool {
+	_, ok := f.Lookup()
+	return ok
+}