move the OnEnding processor into internal/x

sdk/internal/x/onending_processor.go

@@ -0,0 +1,14 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package x // import "go.opentelemetry.io/otel/sdk/internal/x"
+
+import "go.opentelemetry.io/otel/trace"
+
+// OnEndingSpanProcessor represents span processors that allow mutating spans
+// just before they are ended and made immutable.
+type OnEndingSpanProcessor interface {
+	// OnEnding is called while the span is finished, and while spans are still
+	// mutable. It is called synchronously and cannot block.
+	OnEnding(trace.Span)
+}

sdk/trace/span.go

@@ -19,6 +19,7 @@ import (
 	"go.opentelemetry.io/otel/codes"
 	"go.opentelemetry.io/otel/internal/global"
 	"go.opentelemetry.io/otel/sdk/instrumentation"
+	"go.opentelemetry.io/otel/sdk/internal/x"
 	"go.opentelemetry.io/otel/sdk/resource"
 	semconv "go.opentelemetry.io/otel/semconv/v1.26.0"
 	"go.opentelemetry.io/otel/trace"
@@ -427,7 +428,7 @@ func (s *recordingSpan) End(options ...trace.SpanEndOption) {
 
 	sps := s.tracer.provider.getSpanProcessors()
 	for _, sp := range sps {
-		if oesp, ok := sp.sp.(OnEndingSpanProcessor); ok {
+		if oesp, ok := sp.sp.(x.OnEndingSpanProcessor); ok {
 			oesp.OnEnding(s)
 		}
 	}

sdk/trace/span_processor.go

@@ -49,17 +49,6 @@ type SpanProcessor interface {
 	// must never be done outside of a new major release.
 }
 
-// OnEndingSpanProcessor represents span processors that allow mutating spans
-// just before they are ended and made immutable.
-//
-// NOT STABLE: This interface still has a status of "development", and may have
-// breaking changes.
-type OnEndingSpanProcessor interface {
-	// OnEnding is called while the span is finished, and while spans are still
-	// mutable. It is called synchronously and cannot block.
-	OnEnding(ReadWriteSpan)
-}
-
 type spanProcessorState struct {
 	sp    SpanProcessor
 	state sync.Once

sdk/trace/span_processor_test.go

@@ -46,7 +46,7 @@ func (t *testSpanProcessor) OnStart(parent context.Context, s sdktrace.ReadWrite
 	t.spansStarted = append(t.spansStarted, s)
 }
 
-func (t *testSpanProcessor) OnEnding(s sdktrace.ReadWriteSpan) {
+func (t *testSpanProcessor) OnEnding(s trace.Span) {
 	if t == nil {
 		return
 	}